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rust/src/expr.rs
Seiichi Uchida d45aa55bd6 Remove nested parens 
And make sure that we do not remove comments within parens.
2018-03-08 20:25:18 +09:00

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// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
use std::borrow::Cow;
use std::cmp::min;
use std::iter::repeat;
use config::lists::*;
use syntax::{ast, ptr};
use syntax::codemap::{BytePos, CodeMap, Span};
use chains::rewrite_chain;
use closures;
use codemap::{LineRangeUtils, SpanUtils};
use comment::{combine_strs_with_missing_comments, contains_comment, recover_comment_removed,
rewrite_comment, rewrite_missing_comment, CharClasses, FindUncommented};
use config::{Config, ControlBraceStyle, IndentStyle};
use lists::{definitive_tactic, itemize_list, shape_for_tactic, struct_lit_formatting,
struct_lit_shape, struct_lit_tactic, write_list, ListFormatting, ListItem, Separator};
use macros::{rewrite_macro, MacroArg, MacroPosition};
use patterns::{can_be_overflowed_pat, TuplePatField};
use rewrite::{Rewrite, RewriteContext};
use shape::{Indent, Shape};
use spanned::Spanned;
use string::{rewrite_string, StringFormat};
use types::{can_be_overflowed_type, rewrite_path, PathContext};
use utils::{colon_spaces, contains_skip, count_newlines, extra_offset, first_line_width,
inner_attributes, last_line_extendable, last_line_width, mk_sp, outer_attributes,
paren_overhead, ptr_vec_to_ref_vec, semicolon_for_stmt, trimmed_last_line_width,
wrap_str};
use vertical::rewrite_with_alignment;
use visitor::FmtVisitor;
impl Rewrite for ast::Expr {
fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
format_expr(self, ExprType::SubExpression, context, shape)
}
}
#[derive(Copy, Clone, PartialEq)]
pub enum ExprType {
Statement,
SubExpression,
}
pub fn format_expr(
expr: &ast::Expr,
expr_type: ExprType,
context: &RewriteContext,
shape: Shape,
) -> Option<String> {
skip_out_of_file_lines_range!(context, expr.span);
if contains_skip(&*expr.attrs) {
return Some(context.snippet(expr.span()).to_owned());
}
let expr_rw = match expr.node {
ast::ExprKind::Array(ref expr_vec) => rewrite_array(
&ptr_vec_to_ref_vec(expr_vec),
mk_sp(
context.snippet_provider.span_after(expr.span, "["),
expr.span.hi(),
),
context,
shape,
false,
),
ast::ExprKind::Lit(ref l) => rewrite_literal(context, l, shape),
ast::ExprKind::Call(ref callee, ref args) => {
let inner_span = mk_sp(callee.span.hi(), expr.span.hi());
let callee_str = callee.rewrite(context, shape)?;
rewrite_call(context, &callee_str, args, inner_span, shape)
}
ast::ExprKind::Paren(ref subexpr) => rewrite_paren(context, subexpr, shape, expr.span),
ast::ExprKind::Binary(ref op, ref lhs, ref rhs) => {
// FIXME: format comments between operands and operator
rewrite_pair(
&**lhs,
&**rhs,
PairParts::new("", &format!(" {} ", context.snippet(op.span)), ""),
context,
shape,
context.config.binop_separator(),
)
}
ast::ExprKind::Unary(ref op, ref subexpr) => rewrite_unary_op(context, op, subexpr, shape),
ast::ExprKind::Struct(ref path, ref fields, ref base) => rewrite_struct_lit(
context,
path,
fields,
base.as_ref().map(|e| &**e),
expr.span,
shape,
),
ast::ExprKind::Tup(ref items) => {
rewrite_tuple(context, &ptr_vec_to_ref_vec(items), expr.span, shape)
}
ast::ExprKind::If(..)
| ast::ExprKind::IfLet(..)
| ast::ExprKind::ForLoop(..)
| ast::ExprKind::Loop(..)
| ast::ExprKind::While(..)
| ast::ExprKind::WhileLet(..) => to_control_flow(expr, expr_type)
.and_then(|control_flow| control_flow.rewrite(context, shape)),
ast::ExprKind::Block(ref block) => {
match expr_type {
ExprType::Statement => {
if is_unsafe_block(block) {
block.rewrite(context, shape)
} else if let rw @ Some(_) = rewrite_empty_block(context, block, shape) {
// Rewrite block without trying to put it in a single line.
rw
} else {
let prefix = block_prefix(context, block, shape)?;
rewrite_block_with_visitor(context, &prefix, block, shape, true)
}
}
ExprType::SubExpression => block.rewrite(context, shape),
}
}
ast::ExprKind::Match(ref cond, ref arms) => {
rewrite_match(context, cond, arms, shape, expr.span, &expr.attrs)
}
ast::ExprKind::Path(ref qself, ref path) => {
rewrite_path(context, PathContext::Expr, qself.as_ref(), path, shape)
}
ast::ExprKind::Assign(ref lhs, ref rhs) => {
rewrite_assignment(context, lhs, rhs, None, shape)
}
ast::ExprKind::AssignOp(ref op, ref lhs, ref rhs) => {
rewrite_assignment(context, lhs, rhs, Some(op), shape)
}
ast::ExprKind::Continue(ref opt_label) => {
let id_str = match *opt_label {
Some(label) => format!(" {}", label.ident),
None => String::new(),
};
Some(format!("continue{}", id_str))
}
ast::ExprKind::Break(ref opt_label, ref opt_expr) => {
let id_str = match *opt_label {
Some(label) => format!(" {}", label.ident),
None => String::new(),
};
if let Some(ref expr) = *opt_expr {
rewrite_unary_prefix(context, &format!("break{} ", id_str), &**expr, shape)
} else {
Some(format!("break{}", id_str))
}
}
ast::ExprKind::Yield(ref opt_expr) => if let Some(ref expr) = *opt_expr {
rewrite_unary_prefix(context, "yield ", &**expr, shape)
} else {
Some("yield".to_string())
},
ast::ExprKind::Closure(capture, movability, ref fn_decl, ref body, _) => {
closures::rewrite_closure(
capture,
movability,
fn_decl,
body,
expr.span,
context,
shape,
)
}
ast::ExprKind::Try(..)
| ast::ExprKind::Field(..)
| ast::ExprKind::TupField(..)
| ast::ExprKind::MethodCall(..) => rewrite_chain(expr, context, shape),
ast::ExprKind::Mac(ref mac) => {
rewrite_macro(mac, None, context, shape, MacroPosition::Expression).or_else(|| {
wrap_str(
context.snippet(expr.span).to_owned(),
context.config.max_width(),
shape,
)
})
}
ast::ExprKind::Ret(None) => Some("return".to_owned()),
ast::ExprKind::Ret(Some(ref expr)) => {
rewrite_unary_prefix(context, "return ", &**expr, shape)
}
ast::ExprKind::Box(ref expr) => rewrite_unary_prefix(context, "box ", &**expr, shape),
ast::ExprKind::AddrOf(mutability, ref expr) => {
rewrite_expr_addrof(context, mutability, expr, shape)
}
ast::ExprKind::Cast(ref expr, ref ty) => rewrite_pair(
&**expr,
&**ty,
PairParts::new("", " as ", ""),
context,
shape,
SeparatorPlace::Front,
),
ast::ExprKind::Type(ref expr, ref ty) => rewrite_pair(
&**expr,
&**ty,
PairParts::new("", ": ", ""),
context,
shape,
SeparatorPlace::Back,
),
ast::ExprKind::Index(ref expr, ref index) => {
rewrite_index(&**expr, &**index, context, shape)
}
ast::ExprKind::Repeat(ref expr, ref repeats) => {
let (lbr, rbr) = if context.config.spaces_within_parens_and_brackets() {
("[ ", " ]")
} else {
("[", "]")
};
rewrite_pair(
&**expr,
&**repeats,
PairParts::new(lbr, "; ", rbr),
context,
shape,
SeparatorPlace::Back,
)
}
ast::ExprKind::Range(ref lhs, ref rhs, limits) => {
let delim = match limits {
ast::RangeLimits::HalfOpen => "..",
ast::RangeLimits::Closed => "..=",
};
fn needs_space_before_range(context: &RewriteContext, lhs: &ast::Expr) -> bool {
match lhs.node {
ast::ExprKind::Lit(ref lit) => match lit.node {
ast::LitKind::FloatUnsuffixed(..) => {
context.snippet(lit.span).ends_with('.')
}
_ => false,
},
_ => false,
}
}
match (lhs.as_ref().map(|x| &**x), rhs.as_ref().map(|x| &**x)) {
(Some(lhs), Some(rhs)) => {
let sp_delim = if context.config.spaces_around_ranges() {
format!(" {} ", delim)
} else if needs_space_before_range(context, lhs) {
format!(" {}", delim)
} else {
delim.to_owned()
};
rewrite_pair(
&*lhs,
&*rhs,
PairParts::new("", &sp_delim, ""),
context,
shape,
context.config.binop_separator(),
)
}
(None, Some(rhs)) => {
let sp_delim = if context.config.spaces_around_ranges() {
format!("{} ", delim)
} else {
delim.to_owned()
};
rewrite_unary_prefix(context, &sp_delim, &*rhs, shape)
}
(Some(lhs), None) => {
let sp_delim = if context.config.spaces_around_ranges() {
format!(" {}", delim)
} else {
delim.to_owned()
};
rewrite_unary_suffix(context, &sp_delim, &*lhs, shape)
}
(None, None) => Some(delim.to_owned()),
}
}
// We do not format these expressions yet, but they should still
// satisfy our width restrictions.
ast::ExprKind::InPlace(..) | ast::ExprKind::InlineAsm(..) => {
Some(context.snippet(expr.span).to_owned())
}
ast::ExprKind::Catch(ref block) => {
if let rw @ Some(_) = rewrite_single_line_block(context, "do catch ", block, shape) {
rw
} else {
// 9 = `do catch `
let budget = shape.width.checked_sub(9).unwrap_or(0);
Some(format!(
"{}{}",
"do catch ",
block.rewrite(context, Shape::legacy(budget, shape.indent))?
))
}
}
};
expr_rw
.and_then(|expr_str| recover_comment_removed(expr_str, expr.span, context))
.and_then(|expr_str| {
let attrs = outer_attributes(&expr.attrs);
let attrs_str = attrs.rewrite(context, shape)?;
let span = mk_sp(
attrs.last().map_or(expr.span.lo(), |attr| attr.span.hi()),
expr.span.lo(),
);
combine_strs_with_missing_comments(context, &attrs_str, &expr_str, span, shape, false)
})
}
#[derive(new, Clone, Copy)]
pub struct PairParts<'a> {
prefix: &'a str,
infix: &'a str,
suffix: &'a str,
}
pub fn rewrite_pair<LHS, RHS>(
lhs: &LHS,
rhs: &RHS,
pp: PairParts,
context: &RewriteContext,
shape: Shape,
separator_place: SeparatorPlace,
) -> Option<String>
where
LHS: Rewrite,
RHS: Rewrite,
{
let lhs_overhead = match separator_place {
SeparatorPlace::Back => shape.used_width() + pp.prefix.len() + pp.infix.trim_right().len(),
SeparatorPlace::Front => shape.used_width(),
};
let lhs_shape = Shape {
width: context.budget(lhs_overhead),
..shape
};
let lhs_result = lhs.rewrite(context, lhs_shape)
.map(|lhs_str| format!("{}{}", pp.prefix, lhs_str))?;
// Try to the both lhs and rhs on the same line.
let rhs_orig_result = shape
.offset_left(last_line_width(&lhs_result) + pp.infix.len())
.and_then(|s| s.sub_width(pp.suffix.len()))
.and_then(|rhs_shape| rhs.rewrite(context, rhs_shape));
if let Some(ref rhs_result) = rhs_orig_result {
// If the rhs looks like block expression, we allow it to stay on the same line
// with the lhs even if it is multi-lined.
let allow_same_line = rhs_result
.lines()
.next()
.map(|first_line| first_line.ends_with('{'))
.unwrap_or(false);
if !rhs_result.contains('\n') || allow_same_line {
let one_line_width = last_line_width(&lhs_result) + pp.infix.len()
+ first_line_width(rhs_result) + pp.suffix.len();
if one_line_width <= shape.width {
return Some(format!(
"{}{}{}{}",
lhs_result, pp.infix, rhs_result, pp.suffix
));
}
}
}
// We have to use multiple lines.
// Re-evaluate the rhs because we have more space now:
let mut rhs_shape = match context.config.indent_style() {
IndentStyle::Visual => shape
.sub_width(pp.suffix.len() + pp.prefix.len())?
.visual_indent(pp.prefix.len()),
IndentStyle::Block => {
// Try to calculate the initial constraint on the right hand side.
let rhs_overhead = shape.rhs_overhead(context.config);
Shape::indented(shape.indent.block_indent(context.config), context.config)
.sub_width(rhs_overhead)?
}
};
let infix = match separator_place {
SeparatorPlace::Back => pp.infix.trim_right(),
SeparatorPlace::Front => pp.infix.trim_left(),
};
if separator_place == SeparatorPlace::Front {
rhs_shape = rhs_shape.offset_left(infix.len())?;
}
let rhs_result = rhs.rewrite(context, rhs_shape)?;
let indent_str = rhs_shape.indent.to_string_with_newline(context.config);
let infix_with_sep = match separator_place {
SeparatorPlace::Back => format!("{}{}", infix, indent_str),
SeparatorPlace::Front => format!("{}{}", indent_str, infix),
};
Some(format!(
"{}{}{}{}",
lhs_result, infix_with_sep, rhs_result, pp.suffix
))
}
pub fn rewrite_array<T: Rewrite + Spanned + ToExpr>(
exprs: &[&T],
span: Span,
context: &RewriteContext,
shape: Shape,
trailing_comma: bool,
) -> Option<String> {
let bracket_size = if context.config.spaces_within_parens_and_brackets() {
2 // "[ "
} else {
1 // "["
};
let nested_shape = match context.config.indent_style() {
IndentStyle::Block => shape
.block()
.block_indent(context.config.tab_spaces())
.with_max_width(context.config)
.sub_width(1)?,
IndentStyle::Visual => shape
.visual_indent(bracket_size)
.sub_width(bracket_size * 2)?,
};
let items = itemize_list(
context.snippet_provider,
exprs.iter(),
"]",
",",
|item| item.span().lo(),
|item| item.span().hi(),
|item| item.rewrite(context, nested_shape),
span.lo(),
span.hi(),
false,
).collect::<Vec<_>>();
if items.is_empty() {
if context.config.spaces_within_parens_and_brackets() {
return Some("[ ]".to_string());
} else {
return Some("[]".to_string());
}
}
let tactic = array_tactic(context, shape, nested_shape, exprs, &items, bracket_size);
let ends_with_newline = tactic.ends_with_newline(context.config.indent_style());
let fmt = ListFormatting {
tactic,
separator: ",",
trailing_separator: if trailing_comma {
SeparatorTactic::Always
} else if context.inside_macro && !exprs.is_empty() {
let ends_with_bracket = context.snippet(span).ends_with(']');
let bracket_offset = if ends_with_bracket { 1 } else { 0 };
let snippet = context.snippet(mk_sp(span.lo(), span.hi() - BytePos(bracket_offset)));
let last_char_index = snippet.rfind(|c: char| !c.is_whitespace())?;
if &snippet[last_char_index..last_char_index + 1] == "," {
SeparatorTactic::Always
} else {
SeparatorTactic::Never
}
} else if context.config.indent_style() == IndentStyle::Visual {
SeparatorTactic::Never
} else {
SeparatorTactic::Vertical
},
separator_place: SeparatorPlace::Back,
shape: nested_shape,
ends_with_newline,
preserve_newline: false,
config: context.config,
};
let list_str = write_list(&items, &fmt)?;
let result = if context.config.indent_style() == IndentStyle::Visual
|| tactic == DefinitiveListTactic::Horizontal
{
if context.config.spaces_within_parens_and_brackets() && !list_str.is_empty() {
format!("[ {} ]", list_str)
} else {
format!("[{}]", list_str)
}
} else {
format!(
"[{}{}{}]",
nested_shape.indent.to_string_with_newline(context.config),
list_str,
shape.block().indent.to_string_with_newline(context.config)
)
};
Some(result)
}
fn array_tactic<T: Rewrite + Spanned + ToExpr>(
context: &RewriteContext,
shape: Shape,
nested_shape: Shape,
exprs: &[&T],
items: &[ListItem],
bracket_size: usize,
) -> DefinitiveListTactic {
let has_long_item = items
.iter()
.any(|li| li.item.as_ref().map(|s| s.len() > 10).unwrap_or(false));
match context.config.indent_style() {
IndentStyle::Block => {
let tactic = match shape.width.checked_sub(2 * bracket_size) {
Some(width) => {
let tactic = ListTactic::LimitedHorizontalVertical(
context.config.width_heuristics().array_width,
);
definitive_tactic(items, tactic, Separator::Comma, width)
}
None => DefinitiveListTactic::Vertical,
};
if tactic == DefinitiveListTactic::Vertical && !has_long_item
&& is_every_args_simple(exprs)
{
DefinitiveListTactic::Mixed
} else {
tactic
}
}
IndentStyle::Visual => {
if has_long_item || items.iter().any(ListItem::is_multiline) {
definitive_tactic(
items,
ListTactic::LimitedHorizontalVertical(
context.config.width_heuristics().array_width,
),
Separator::Comma,
nested_shape.width,
)
} else {
DefinitiveListTactic::Mixed
}
}
}
}
fn nop_block_collapse(block_str: Option<String>, budget: usize) -> Option<String> {
debug!("nop_block_collapse {:?} {}", block_str, budget);
block_str.map(|block_str| {
if block_str.starts_with('{') && budget >= 2
&& (block_str[1..].find(|c: char| !c.is_whitespace()).unwrap() == block_str.len() - 2)
{
"{}".to_owned()
} else {
block_str.to_owned()
}
})
}
fn rewrite_empty_block(
context: &RewriteContext,
block: &ast::Block,
shape: Shape,
) -> Option<String> {
if block.stmts.is_empty() && !block_contains_comment(block, context.codemap) && shape.width >= 2
{
return Some("{}".to_owned());
}
// If a block contains only a single-line comment, then leave it on one line.
let user_str = context.snippet(block.span);
let user_str = user_str.trim();
if user_str.starts_with('{') && user_str.ends_with('}') {
let comment_str = user_str[1..user_str.len() - 1].trim();
if block.stmts.is_empty() && !comment_str.contains('\n') && !comment_str.starts_with("//")
&& comment_str.len() + 4 <= shape.width
{
return Some(format!("{{ {} }}", comment_str));
}
}
None
}
fn block_prefix(context: &RewriteContext, block: &ast::Block, shape: Shape) -> Option<String> {
Some(match block.rules {
ast::BlockCheckMode::Unsafe(..) => {
let snippet = context.snippet(block.span);
let open_pos = snippet.find_uncommented("{")?;
// Extract comment between unsafe and block start.
let trimmed = &snippet[6..open_pos].trim();
if !trimmed.is_empty() {
// 9 = "unsafe {".len(), 7 = "unsafe ".len()
let budget = shape.width.checked_sub(9)?;
format!(
"unsafe {} ",
rewrite_comment(
trimmed,
true,
Shape::legacy(budget, shape.indent + 7),
context.config,
)?
)
} else {
"unsafe ".to_owned()
}
}
ast::BlockCheckMode::Default => String::new(),
})
}
fn rewrite_single_line_block(
context: &RewriteContext,
prefix: &str,
block: &ast::Block,
shape: Shape,
) -> Option<String> {
if is_simple_block(block, context.codemap) {
let expr_shape = shape.offset_left(last_line_width(prefix))?;
let expr_str = block.stmts[0].rewrite(context, expr_shape)?;
let result = format!("{}{{ {} }}", prefix, expr_str);
if result.len() <= shape.width && !result.contains('\n') {
return Some(result);
}
}
None
}
pub fn rewrite_block_with_visitor(
context: &RewriteContext,
prefix: &str,
block: &ast::Block,
shape: Shape,
has_braces: bool,
) -> Option<String> {
if let rw @ Some(_) = rewrite_empty_block(context, block, shape) {
return rw;
}
let mut visitor = FmtVisitor::from_context(context);
visitor.block_indent = shape.indent;
visitor.is_if_else_block = context.is_if_else_block;
match block.rules {
ast::BlockCheckMode::Unsafe(..) => {
let snippet = context.snippet(block.span);
let open_pos = snippet.find_uncommented("{")?;
visitor.last_pos = block.span.lo() + BytePos(open_pos as u32)
}
ast::BlockCheckMode::Default => visitor.last_pos = block.span.lo(),
}
visitor.visit_block(block, None, has_braces);
Some(format!("{}{}", prefix, visitor.buffer))
}
impl Rewrite for ast::Block {
fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
// shape.width is used only for the single line case: either the empty block `{}`,
// or an unsafe expression `unsafe { e }`.
if let rw @ Some(_) = rewrite_empty_block(context, self, shape) {
return rw;
}
let prefix = block_prefix(context, self, shape)?;
let result = rewrite_block_with_visitor(context, &prefix, self, shape, true);
if let Some(ref result_str) = result {
if result_str.lines().count() <= 3 {
if let rw @ Some(_) = rewrite_single_line_block(context, &prefix, self, shape) {
return rw;
}
}
}
result
}
}
impl Rewrite for ast::Stmt {
fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
skip_out_of_file_lines_range!(context, self.span());
let result = match self.node {
ast::StmtKind::Local(ref local) => local.rewrite(context, shape),
ast::StmtKind::Expr(ref ex) | ast::StmtKind::Semi(ref ex) => {
let suffix = if semicolon_for_stmt(context, self) {
";"
} else {
""
};
let shape = shape.sub_width(suffix.len())?;
format_expr(ex, ExprType::Statement, context, shape).map(|s| s + suffix)
}
ast::StmtKind::Mac(..) | ast::StmtKind::Item(..) => None,
};
result.and_then(|res| recover_comment_removed(res, self.span(), context))
}
}
// Rewrite condition if the given expression has one.
pub fn rewrite_cond(context: &RewriteContext, expr: &ast::Expr, shape: Shape) -> Option<String> {
match expr.node {
ast::ExprKind::Match(ref cond, _) => {
// `match `cond` {`
let cond_shape = match context.config.indent_style() {
IndentStyle::Visual => shape.shrink_left(6).and_then(|s| s.sub_width(2))?,
IndentStyle::Block => shape.offset_left(8)?,
};
cond.rewrite(context, cond_shape)
}
_ => to_control_flow(expr, ExprType::SubExpression).and_then(|control_flow| {
let alt_block_sep =
String::from("\n") + &shape.indent.block_only().to_string(context.config);
control_flow
.rewrite_cond(context, shape, &alt_block_sep)
.and_then(|rw| Some(rw.0))
}),
}
}
// Abstraction over control flow expressions
#[derive(Debug)]
struct ControlFlow<'a> {
cond: Option<&'a ast::Expr>,
block: &'a ast::Block,
else_block: Option<&'a ast::Expr>,
label: Option<ast::Label>,
pats: Vec<&'a ast::Pat>,
keyword: &'a str,
matcher: &'a str,
connector: &'a str,
allow_single_line: bool,
// True if this is an `if` expression in an `else if` :-( hacky
nested_if: bool,
span: Span,
}
fn to_control_flow(expr: &ast::Expr, expr_type: ExprType) -> Option<ControlFlow> {
match expr.node {
ast::ExprKind::If(ref cond, ref if_block, ref else_block) => Some(ControlFlow::new_if(
cond,
vec![],
if_block,
else_block.as_ref().map(|e| &**e),
expr_type == ExprType::SubExpression,
false,
expr.span,
)),
ast::ExprKind::IfLet(ref pat, ref cond, ref if_block, ref else_block) => {
Some(ControlFlow::new_if(
cond,
ptr_vec_to_ref_vec(pat),
if_block,
else_block.as_ref().map(|e| &**e),
expr_type == ExprType::SubExpression,
false,
expr.span,
))
}
ast::ExprKind::ForLoop(ref pat, ref cond, ref block, label) => {
Some(ControlFlow::new_for(pat, cond, block, label, expr.span))
}
ast::ExprKind::Loop(ref block, label) => {
Some(ControlFlow::new_loop(block, label, expr.span))
}
ast::ExprKind::While(ref cond, ref block, label) => Some(ControlFlow::new_while(
vec![],
cond,
block,
label,
expr.span,
)),
ast::ExprKind::WhileLet(ref pat, ref cond, ref block, label) => Some(
ControlFlow::new_while(ptr_vec_to_ref_vec(pat), cond, block, label, expr.span),
),
_ => None,
}
}
fn choose_matcher(pats: &[&ast::Pat]) -> &'static str {
if pats.is_empty() {
""
} else {
"let"
}
}
impl<'a> ControlFlow<'a> {
fn new_if(
cond: &'a ast::Expr,
pats: Vec<&'a ast::Pat>,
block: &'a ast::Block,
else_block: Option<&'a ast::Expr>,
allow_single_line: bool,
nested_if: bool,
span: Span,
) -> ControlFlow<'a> {
let matcher = choose_matcher(&pats);
ControlFlow {
cond: Some(cond),
block,
else_block,
label: None,
pats,
keyword: "if",
matcher,
connector: " =",
allow_single_line,
nested_if,
span,
}
}
fn new_loop(block: &'a ast::Block, label: Option<ast::Label>, span: Span) -> ControlFlow<'a> {
ControlFlow {
cond: None,
block,
else_block: None,
label,
pats: vec![],
keyword: "loop",
matcher: "",
connector: "",
allow_single_line: false,
nested_if: false,
span,
}
}
fn new_while(
pats: Vec<&'a ast::Pat>,
cond: &'a ast::Expr,
block: &'a ast::Block,
label: Option<ast::Label>,
span: Span,
) -> ControlFlow<'a> {
let matcher = choose_matcher(&pats);
ControlFlow {
cond: Some(cond),
block,
else_block: None,
label,
pats,
keyword: "while",
matcher,
connector: " =",
allow_single_line: false,
nested_if: false,
span,
}
}
fn new_for(
pat: &'a ast::Pat,
cond: &'a ast::Expr,
block: &'a ast::Block,
label: Option<ast::Label>,
span: Span,
) -> ControlFlow<'a> {
ControlFlow {
cond: Some(cond),
block,
else_block: None,
label,
pats: vec![pat],
keyword: "for",
matcher: "",
connector: " in",
allow_single_line: false,
nested_if: false,
span,
}
}
fn rewrite_single_line(
&self,
pat_expr_str: &str,
context: &RewriteContext,
width: usize,
) -> Option<String> {
assert!(self.allow_single_line);
let else_block = self.else_block?;
let fixed_cost = self.keyword.len() + " { } else { }".len();
if let ast::ExprKind::Block(ref else_node) = else_block.node {
if !is_simple_block(self.block, context.codemap)
|| !is_simple_block(else_node, context.codemap)
|| pat_expr_str.contains('\n')
{
return None;
}
let new_width = width.checked_sub(pat_expr_str.len() + fixed_cost)?;
let expr = &self.block.stmts[0];
let if_str = expr.rewrite(context, Shape::legacy(new_width, Indent::empty()))?;
let new_width = new_width.checked_sub(if_str.len())?;
let else_expr = &else_node.stmts[0];
let else_str = else_expr.rewrite(context, Shape::legacy(new_width, Indent::empty()))?;
if if_str.contains('\n') || else_str.contains('\n') {
return None;
}
let result = format!(
"{} {} {{ {} }} else {{ {} }}",
self.keyword, pat_expr_str, if_str, else_str
);
if result.len() <= width {
return Some(result);
}
}
None
}
}
impl<'a> ControlFlow<'a> {
fn rewrite_pat_expr(
&self,
context: &RewriteContext,
expr: &ast::Expr,
shape: Shape,
offset: usize,
) -> Option<String> {
debug!("rewrite_pat_expr {:?} {:?} {:?}", shape, self.pats, expr);
let cond_shape = shape.offset_left(offset)?;
if !self.pats.is_empty() {
let matcher = if self.matcher.is_empty() {
self.matcher.to_owned()
} else {
format!("{} ", self.matcher)
};
let pat_shape = cond_shape
.offset_left(matcher.len())?
.sub_width(self.connector.len())?;
let pat_string = rewrite_multiple_patterns(context, &self.pats, pat_shape)?;
let result = format!("{}{}{}", matcher, pat_string, self.connector);
return rewrite_assign_rhs(context, result, expr, cond_shape);
}
let expr_rw = expr.rewrite(context, cond_shape);
// The expression may (partially) fit on the current line.
// We do not allow splitting between `if` and condition.
if self.keyword == "if" || expr_rw.is_some() {
return expr_rw;
}
// The expression won't fit on the current line, jump to next.
let nested_shape = shape
.block_indent(context.config.tab_spaces())
.with_max_width(context.config);
let nested_indent_str = nested_shape.indent.to_string_with_newline(context.config);
expr.rewrite(context, nested_shape)
.map(|expr_rw| format!("{}{}", nested_indent_str, expr_rw))
}
fn rewrite_cond(
&self,
context: &RewriteContext,
shape: Shape,
alt_block_sep: &str,
) -> Option<(String, usize)> {
// Do not take the rhs overhead from the upper expressions into account
// when rewriting pattern.
let new_width = context.budget(shape.used_width());
let fresh_shape = Shape {
width: new_width,
..shape
};
let constr_shape = if self.nested_if {
// We are part of an if-elseif-else chain. Our constraints are tightened.
// 7 = "} else " .len()
fresh_shape.offset_left(7)?
} else {
fresh_shape
};
let label_string = rewrite_label(self.label);
// 1 = space after keyword.
let offset = self.keyword.len() + label_string.len() + 1;
let pat_expr_string = match self.cond {
Some(cond) => self.rewrite_pat_expr(context, cond, constr_shape, offset)?,
None => String::new(),
};
let brace_overhead =
if context.config.control_brace_style() != ControlBraceStyle::AlwaysNextLine {
// 2 = ` {`
2
} else {
0
};
let one_line_budget = context
.config
.max_width()
.checked_sub(constr_shape.used_width() + offset + brace_overhead)
.unwrap_or(0);
let force_newline_brace = (pat_expr_string.contains('\n')
|| pat_expr_string.len() > one_line_budget)
&& !last_line_extendable(&pat_expr_string);
// Try to format if-else on single line.
if self.allow_single_line
&& context
.config
.width_heuristics()
.single_line_if_else_max_width > 0
{
let trial = self.rewrite_single_line(&pat_expr_string, context, shape.width);
if let Some(cond_str) = trial {
if cond_str.len()
<= context
.config
.width_heuristics()
.single_line_if_else_max_width
{
return Some((cond_str, 0));
}
}
}
let cond_span = if let Some(cond) = self.cond {
cond.span
} else {
mk_sp(self.block.span.lo(), self.block.span.lo())
};
// `for event in event`
// Do not include label in the span.
let lo = self.label.map_or(self.span.lo(), |label| label.span.hi());
let between_kwd_cond = mk_sp(
context
.snippet_provider
.span_after(mk_sp(lo, self.span.hi()), self.keyword.trim()),
if self.pats.is_empty() {
cond_span.lo()
} else if self.matcher.is_empty() {
self.pats[0].span.lo()
} else {
context
.snippet_provider
.span_before(self.span, self.matcher.trim())
},
);
let between_kwd_cond_comment = extract_comment(between_kwd_cond, context, shape);
let after_cond_comment =
extract_comment(mk_sp(cond_span.hi(), self.block.span.lo()), context, shape);
let block_sep = if self.cond.is_none() && between_kwd_cond_comment.is_some() {
""
} else if context.config.control_brace_style() == ControlBraceStyle::AlwaysNextLine
|| force_newline_brace
{
alt_block_sep
} else {
" "
};
let used_width = if pat_expr_string.contains('\n') {
last_line_width(&pat_expr_string)
} else {
// 2 = spaces after keyword and condition.
label_string.len() + self.keyword.len() + pat_expr_string.len() + 2
};
Some((
format!(
"{}{}{}{}{}",
label_string,
self.keyword,
between_kwd_cond_comment.as_ref().map_or(
if pat_expr_string.is_empty() || pat_expr_string.starts_with('\n') {
""
} else {
" "
},
|s| &**s,
),
pat_expr_string,
after_cond_comment.as_ref().map_or(block_sep, |s| &**s)
),
used_width,
))
}
}
impl<'a> Rewrite for ControlFlow<'a> {
fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
debug!("ControlFlow::rewrite {:?} {:?}", self, shape);
let alt_block_sep = &shape.indent.to_string_with_newline(context.config);
let (cond_str, used_width) = self.rewrite_cond(context, shape, alt_block_sep)?;
// If `used_width` is 0, it indicates that whole control flow is written in a single line.
if used_width == 0 {
return Some(cond_str);
}
let block_width = shape.width.checked_sub(used_width).unwrap_or(0);
// This is used only for the empty block case: `{}`. So, we use 1 if we know
// we should avoid the single line case.
let block_width = if self.else_block.is_some() || self.nested_if {
min(1, block_width)
} else {
block_width
};
let block_shape = Shape {
width: block_width,
..shape
};
let mut block_context = context.clone();
block_context.is_if_else_block = self.else_block.is_some();
let block_str =
rewrite_block_with_visitor(&block_context, "", self.block, block_shape, true)?;
let mut result = format!("{}{}", cond_str, block_str);
if let Some(else_block) = self.else_block {
let shape = Shape::indented(shape.indent, context.config);
let mut last_in_chain = false;
let rewrite = match else_block.node {
// If the else expression is another if-else expression, prevent it
// from being formatted on a single line.
// Note how we're passing the original shape, as the
// cost of "else" should not cascade.
ast::ExprKind::IfLet(ref pat, ref cond, ref if_block, ref next_else_block) => {
ControlFlow::new_if(
cond,
ptr_vec_to_ref_vec(pat),
if_block,
next_else_block.as_ref().map(|e| &**e),
false,
true,
mk_sp(else_block.span.lo(), self.span.hi()),
).rewrite(context, shape)
}
ast::ExprKind::If(ref cond, ref if_block, ref next_else_block) => {
ControlFlow::new_if(
cond,
vec![],
if_block,
next_else_block.as_ref().map(|e| &**e),
false,
true,
mk_sp(else_block.span.lo(), self.span.hi()),
).rewrite(context, shape)
}
_ => {
last_in_chain = true;
// When rewriting a block, the width is only used for single line
// blocks, passing 1 lets us avoid that.
let else_shape = Shape {
width: min(1, shape.width),
..shape
};
format_expr(else_block, ExprType::Statement, context, else_shape)
}
};
let between_kwd_else_block = mk_sp(
self.block.span.hi(),
context
.snippet_provider
.span_before(mk_sp(self.block.span.hi(), else_block.span.lo()), "else"),
);
let between_kwd_else_block_comment =
extract_comment(between_kwd_else_block, context, shape);
let after_else = mk_sp(
context
.snippet_provider
.span_after(mk_sp(self.block.span.hi(), else_block.span.lo()), "else"),
else_block.span.lo(),
);
let after_else_comment = extract_comment(after_else, context, shape);
let between_sep = match context.config.control_brace_style() {
ControlBraceStyle::AlwaysNextLine | ControlBraceStyle::ClosingNextLine => {
&*alt_block_sep
}
ControlBraceStyle::AlwaysSameLine => " ",
};
let after_sep = match context.config.control_brace_style() {
ControlBraceStyle::AlwaysNextLine if last_in_chain => &*alt_block_sep,
_ => " ",
};
result.push_str(&format!(
"{}else{}",
between_kwd_else_block_comment
.as_ref()
.map_or(between_sep, |s| &**s),
after_else_comment.as_ref().map_or(after_sep, |s| &**s),
));
result.push_str(&rewrite?);
}
Some(result)
}
}
fn rewrite_label(opt_label: Option<ast::Label>) -> Cow<'static, str> {
match opt_label {
Some(label) => Cow::from(format!("{}: ", label.ident)),
None => Cow::from(""),
}
}
fn extract_comment(span: Span, context: &RewriteContext, shape: Shape) -> Option<String> {
match rewrite_missing_comment(span, shape, context) {
Some(ref comment) if !comment.is_empty() => Some(format!(
"{indent}{}{indent}",
comment,
indent = shape.indent.to_string_with_newline(context.config)
)),
_ => None,
}
}
pub fn block_contains_comment(block: &ast::Block, codemap: &CodeMap) -> bool {
let snippet = codemap.span_to_snippet(block.span).unwrap();
contains_comment(&snippet)
}
// Checks that a block contains no statements, an expression and no comments.
// FIXME: incorrectly returns false when comment is contained completely within
// the expression.
pub fn is_simple_block(block: &ast::Block, codemap: &CodeMap) -> bool {
(block.stmts.len() == 1 && stmt_is_expr(&block.stmts[0])
&& !block_contains_comment(block, codemap))
}
/// Checks whether a block contains at most one statement or expression, and no comments.
pub fn is_simple_block_stmt(block: &ast::Block, codemap: &CodeMap) -> bool {
block.stmts.len() <= 1 && !block_contains_comment(block, codemap)
}
/// Checks whether a block contains no statements, expressions, or comments.
pub fn is_empty_block(block: &ast::Block, codemap: &CodeMap) -> bool {
block.stmts.is_empty() && !block_contains_comment(block, codemap)
}
pub fn stmt_is_expr(stmt: &ast::Stmt) -> bool {
match stmt.node {
ast::StmtKind::Expr(..) => true,
_ => false,
}
}
pub fn is_unsafe_block(block: &ast::Block) -> bool {
if let ast::BlockCheckMode::Unsafe(..) = block.rules {
true
} else {
false
}
}
/// A simple wrapper type against `ast::Arm`. Used inside `write_list()`.
struct ArmWrapper<'a> {
pub arm: &'a ast::Arm,
/// True if the arm is the last one in match expression. Used to decide on whether we should add
/// trailing comma to the match arm when `config.trailing_comma() == Never`.
pub is_last: bool,
/// Holds a byte position of `|` at the beginning of the arm pattern, if available.
pub beginning_vert: Option<BytePos>,
}
impl<'a> ArmWrapper<'a> {
pub fn new(
arm: &'a ast::Arm,
is_last: bool,
beginning_vert: Option<BytePos>,
) -> ArmWrapper<'a> {
ArmWrapper {
arm,
is_last,
beginning_vert,
}
}
}
impl<'a> Spanned for ArmWrapper<'a> {
fn span(&self) -> Span {
if let Some(lo) = self.beginning_vert {
mk_sp(lo, self.arm.span().hi())
} else {
self.arm.span()
}
}
}
impl<'a> Rewrite for ArmWrapper<'a> {
fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
rewrite_match_arm(context, self.arm, shape, self.is_last, self.beginning_vert)
}
}
fn rewrite_match(
context: &RewriteContext,
cond: &ast::Expr,
arms: &[ast::Arm],
shape: Shape,
span: Span,
attrs: &[ast::Attribute],
) -> Option<String> {
// Do not take the rhs overhead from the upper expressions into account
// when rewriting match condition.
let cond_shape = Shape {
width: context.budget(shape.used_width()),
..shape
};
// 6 = `match `
let cond_shape = match context.config.indent_style() {
IndentStyle::Visual => cond_shape.shrink_left(6)?,
IndentStyle::Block => cond_shape.offset_left(6)?,
};
let cond_str = cond.rewrite(context, cond_shape)?;
let alt_block_sep = &shape.indent.to_string_with_newline(context.config);
let block_sep = match context.config.control_brace_style() {
ControlBraceStyle::AlwaysNextLine => alt_block_sep,
_ if last_line_extendable(&cond_str) => " ",
// 2 = ` {`
_ if cond_str.contains('\n') || cond_str.len() + 2 > cond_shape.width => alt_block_sep,
_ => " ",
};
let nested_indent_str = shape
.indent
.block_indent(context.config)
.to_string(context.config);
// Inner attributes.
let inner_attrs = &inner_attributes(attrs);
let inner_attrs_str = if inner_attrs.is_empty() {
String::new()
} else {
inner_attrs
.rewrite(context, shape)
.map(|s| format!("{}{}\n", nested_indent_str, s))?
};
let open_brace_pos = if inner_attrs.is_empty() {
let hi = if arms.is_empty() {
span.hi()
} else {
arms[0].span().lo()
};
context
.snippet_provider
.span_after(mk_sp(cond.span.hi(), hi), "{")
} else {
inner_attrs[inner_attrs.len() - 1].span().hi()
};
if arms.is_empty() {
let snippet = context.snippet(mk_sp(open_brace_pos, span.hi() - BytePos(1)));
if snippet.trim().is_empty() {
Some(format!("match {} {{}}", cond_str))
} else {
// Empty match with comments or inner attributes? We are not going to bother, sorry ;)
Some(context.snippet(span).to_owned())
}
} else {
Some(format!(
"match {}{}{{\n{}{}{}\n{}}}",
cond_str,
block_sep,
inner_attrs_str,
nested_indent_str,
rewrite_match_arms(context, arms, shape, span, open_brace_pos)?,
shape.indent.to_string(context.config),
))
}
}
fn arm_comma(config: &Config, body: &ast::Expr, is_last: bool) -> &'static str {
if is_last && config.trailing_comma() == SeparatorTactic::Never {
""
} else if config.match_block_trailing_comma() {
","
} else if let ast::ExprKind::Block(ref block) = body.node {
if let ast::BlockCheckMode::Default = block.rules {
""
} else {
","
}
} else {
","
}
}
/// Collect a byte position of the beginning `|` for each arm, if available.
fn collect_beginning_verts(
context: &RewriteContext,
arms: &[ast::Arm],
span: Span,
) -> Vec<Option<BytePos>> {
let mut beginning_verts = Vec::with_capacity(arms.len());
let mut lo = context.snippet_provider.span_after(span, "{");
for arm in arms {
let hi = arm.pats[0].span.lo();
let missing_span = mk_sp(lo, hi);
beginning_verts.push(context.snippet_provider.opt_span_before(missing_span, "|"));
lo = arm.span().hi();
}
beginning_verts
}
fn rewrite_match_arms(
context: &RewriteContext,
arms: &[ast::Arm],
shape: Shape,
span: Span,
open_brace_pos: BytePos,
) -> Option<String> {
let arm_shape = shape
.block_indent(context.config.tab_spaces())
.with_max_width(context.config);
let arm_len = arms.len();
let is_last_iter = repeat(false)
.take(arm_len.checked_sub(1).unwrap_or(0))
.chain(repeat(true));
let beginning_verts = collect_beginning_verts(context, arms, span);
let items = itemize_list(
context.snippet_provider,
arms.iter()
.zip(is_last_iter)
.zip(beginning_verts.into_iter())
.map(|((arm, is_last), beginning_vert)| ArmWrapper::new(arm, is_last, beginning_vert)),
"}",
"|",
|arm| arm.span().lo(),
|arm| arm.span().hi(),
|arm| arm.rewrite(context, arm_shape),
open_brace_pos,
span.hi(),
false,
);
let arms_vec: Vec<_> = items.collect();
let fmt = ListFormatting {
tactic: DefinitiveListTactic::Vertical,
// We will add/remove commas inside `arm.rewrite()`, and hence no separator here.
separator: "",
trailing_separator: SeparatorTactic::Never,
separator_place: SeparatorPlace::Back,
shape: arm_shape,
ends_with_newline: true,
preserve_newline: true,
config: context.config,
};
write_list(&arms_vec, &fmt)
}
fn rewrite_match_arm(
context: &RewriteContext,
arm: &ast::Arm,
shape: Shape,
is_last: bool,
beginning_vert: Option<BytePos>,
) -> Option<String> {
let (missing_span, attrs_str) = if !arm.attrs.is_empty() {
if contains_skip(&arm.attrs) {
let (_, body) = flatten_arm_body(context, &arm.body);
// `arm.span()` does not include trailing comma, add it manually.
return Some(format!(
"{}{}",
context.snippet(arm.span()),
arm_comma(context.config, body, is_last),
));
}
let missing_span = mk_sp(
arm.attrs[arm.attrs.len() - 1].span.hi(),
arm.pats[0].span.lo(),
);
(missing_span, arm.attrs.rewrite(context, shape)?)
} else {
(mk_sp(arm.span().lo(), arm.span().lo()), String::new())
};
let pats_str = rewrite_match_pattern(
context,
&ptr_vec_to_ref_vec(&arm.pats),
&arm.guard,
beginning_vert.is_some(),
shape,
).and_then(|pats_str| {
combine_strs_with_missing_comments(
context,
&attrs_str,
&pats_str,
missing_span,
shape,
false,
)
})?;
rewrite_match_body(
context,
&arm.body,
&pats_str,
shape,
arm.guard.is_some(),
is_last,
)
}
/// Returns true if the given pattern is short. A short pattern is defined by the following grammer:
///
/// [small, ntp]:
/// - single token
/// - `&[single-line, ntp]`
///
/// [small]:
/// - `[small, ntp]`
/// - unary tuple constructor `([small, ntp])`
/// - `&[small]`
fn is_short_pattern(pat: &ast::Pat, pat_str: &str) -> bool {
// We also require that the pattern is reasonably 'small' with its literal width.
pat_str.len() <= 20 && !pat_str.contains('\n') && is_short_pattern_inner(pat)
}
fn is_short_pattern_inner(pat: &ast::Pat) -> bool {
match pat.node {
ast::PatKind::Wild | ast::PatKind::Lit(_) => true,
ast::PatKind::Ident(_, _, ref pat) => pat.is_none(),
ast::PatKind::Struct(..)
| ast::PatKind::Mac(..)
| ast::PatKind::Slice(..)
| ast::PatKind::Path(..)
| ast::PatKind::Range(..) => false,
ast::PatKind::Tuple(ref subpats, _) => subpats.len() <= 1,
ast::PatKind::TupleStruct(ref path, ref subpats, _) => {
path.segments.len() <= 1 && subpats.len() <= 1
}
ast::PatKind::Box(ref p) | ast::PatKind::Ref(ref p, _) | ast::PatKind::Paren(ref p) => {
is_short_pattern_inner(&*p)
}
}
}
fn rewrite_match_pattern(
context: &RewriteContext,
pats: &[&ast::Pat],
guard: &Option<ptr::P<ast::Expr>>,
has_beginning_vert: bool,
shape: Shape,
) -> Option<String> {
// Patterns
// 5 = ` => {`
// 2 = `| `
let pat_shape = shape
.sub_width(5)?
.offset_left(if has_beginning_vert { 2 } else { 0 })?;
let pats_str = rewrite_multiple_patterns(context, pats, pat_shape)?;
let beginning_vert = if has_beginning_vert { "| " } else { "" };
// Guard
let guard_str = rewrite_guard(context, guard, shape, trimmed_last_line_width(&pats_str))?;
Some(format!("{}{}{}", beginning_vert, pats_str, guard_str))
}
// (extend, body)
// @extend: true if the arm body can be put next to `=>`
// @body: flattened body, if the body is block with a single expression
fn flatten_arm_body<'a>(context: &'a RewriteContext, body: &'a ast::Expr) -> (bool, &'a ast::Expr) {
match body.node {
ast::ExprKind::Block(ref block)
if !is_unsafe_block(block) && is_simple_block(block, context.codemap) =>
{
if let ast::StmtKind::Expr(ref expr) = block.stmts[0].node {
(
!context.config.force_multiline_blocks() && can_extend_match_arm_body(expr),
&*expr,
)
} else {
(false, &*body)
}
}
_ => (
!context.config.force_multiline_blocks() && body.can_be_overflowed(context, 1),
&*body,
),
}
}
fn rewrite_match_body(
context: &RewriteContext,
body: &ptr::P<ast::Expr>,
pats_str: &str,
shape: Shape,
has_guard: bool,
is_last: bool,
) -> Option<String> {
let (extend, body) = flatten_arm_body(context, body);
let (is_block, is_empty_block) = if let ast::ExprKind::Block(ref block) = body.node {
(true, is_empty_block(block, context.codemap))
} else {
(false, false)
};
let comma = arm_comma(context.config, body, is_last);
let alt_block_sep = &shape.indent.to_string_with_newline(context.config);
let combine_orig_body = |body_str: &str| {
let block_sep = match context.config.control_brace_style() {
ControlBraceStyle::AlwaysNextLine if is_block => alt_block_sep,
_ => " ",
};
Some(format!("{} =>{}{}{}", pats_str, block_sep, body_str, comma))
};
let forbid_same_line = has_guard && pats_str.contains('\n') && !is_empty_block;
let next_line_indent = if !is_block || is_empty_block {
shape.indent.block_indent(context.config)
} else {
shape.indent
};
let combine_next_line_body = |body_str: &str| {
if is_block {
return Some(format!(
"{} =>{}{}",
pats_str,
next_line_indent.to_string_with_newline(context.config),
body_str
));
}
let indent_str = shape.indent.to_string_with_newline(context.config);
let nested_indent_str = next_line_indent.to_string_with_newline(context.config);
let (body_prefix, body_suffix) = if context.config.match_arm_blocks() {
let comma = if context.config.match_block_trailing_comma() {
","
} else {
""
};
("{", format!("{}}}{}", indent_str, comma))
} else {
("", String::from(","))
};
let block_sep = match context.config.control_brace_style() {
ControlBraceStyle::AlwaysNextLine => format!("{}{}", alt_block_sep, body_prefix),
_ if body_prefix.is_empty() => "".to_owned(),
_ if forbid_same_line => format!("{}{}", alt_block_sep, body_prefix),
_ => format!(" {}", body_prefix),
} + &nested_indent_str;
Some(format!(
"{} =>{}{}{}",
pats_str, block_sep, body_str, body_suffix
))
};
// Let's try and get the arm body on the same line as the condition.
// 4 = ` => `.len()
let orig_body_shape = shape
.offset_left(extra_offset(pats_str, shape) + 4)
.and_then(|shape| shape.sub_width(comma.len()));
let orig_body = if let Some(body_shape) = orig_body_shape {
let rewrite = nop_block_collapse(
format_expr(body, ExprType::Statement, context, body_shape),
body_shape.width,
);
match rewrite {
Some(ref body_str)
if !forbid_same_line
&& (is_block
|| (!body_str.contains('\n') && body_str.len() <= body_shape.width)) =>
{
return combine_orig_body(body_str);
}
_ => rewrite,
}
} else {
None
};
let orig_budget = orig_body_shape.map_or(0, |shape| shape.width);
// Try putting body on the next line and see if it looks better.
let next_line_body_shape = Shape::indented(next_line_indent, context.config);
let next_line_body = nop_block_collapse(
format_expr(body, ExprType::Statement, context, next_line_body_shape),
next_line_body_shape.width,
);
match (orig_body, next_line_body) {
(Some(ref orig_str), Some(ref next_line_str))
if forbid_same_line || prefer_next_line(orig_str, next_line_str) =>
{
combine_next_line_body(next_line_str)
}
(Some(ref orig_str), _) if extend && first_line_width(orig_str) <= orig_budget => {
combine_orig_body(orig_str)
}
(Some(ref orig_str), Some(ref next_line_str)) if orig_str.contains('\n') => {
combine_next_line_body(next_line_str)
}
(None, Some(ref next_line_str)) => combine_next_line_body(next_line_str),
(None, None) => None,
(Some(ref orig_str), _) => combine_orig_body(orig_str),
}
}
// The `if ...` guard on a match arm.
fn rewrite_guard(
context: &RewriteContext,
guard: &Option<ptr::P<ast::Expr>>,
shape: Shape,
// The amount of space used up on this line for the pattern in
// the arm (excludes offset).
pattern_width: usize,
) -> Option<String> {
if let Some(ref guard) = *guard {
// First try to fit the guard string on the same line as the pattern.
// 4 = ` if `, 5 = ` => {`
let cond_shape = shape
.offset_left(pattern_width + 4)
.and_then(|s| s.sub_width(5));
if let Some(cond_shape) = cond_shape {
if let Some(cond_str) = guard.rewrite(context, cond_shape) {
if !cond_str.contains('\n') || pattern_width <= context.config.tab_spaces() {
return Some(format!(" if {}", cond_str));
}
}
}
// Not enough space to put the guard after the pattern, try a newline.
// 3 = `if `, 5 = ` => {`
let cond_shape = Shape::indented(shape.indent.block_indent(context.config), context.config)
.offset_left(3)
.and_then(|s| s.sub_width(5));
if let Some(cond_shape) = cond_shape {
if let Some(cond_str) = guard.rewrite(context, cond_shape) {
return Some(format!(
"{}if {}",
cond_shape.indent.to_string_with_newline(context.config),
cond_str
));
}
}
None
} else {
Some(String::new())
}
}
fn rewrite_multiple_patterns(
context: &RewriteContext,
pats: &[&ast::Pat],
shape: Shape,
) -> Option<String> {
let pat_strs = pats.iter()
.map(|p| p.rewrite(context, shape))
.collect::<Option<Vec<_>>>()?;
let use_mixed_layout = pats.iter()
.zip(pat_strs.iter())
.all(|(pat, pat_str)| is_short_pattern(pat, pat_str));
let items: Vec<_> = pat_strs.into_iter().map(ListItem::from_str).collect();
let tactic = if use_mixed_layout {
DefinitiveListTactic::Mixed
} else {
definitive_tactic(
&items,
ListTactic::HorizontalVertical,
Separator::VerticalBar,
shape.width,
)
};
let fmt = ListFormatting {
tactic,
separator: " |",
trailing_separator: SeparatorTactic::Never,
separator_place: context.config.binop_separator(),
shape,
ends_with_newline: false,
preserve_newline: false,
config: context.config,
};
write_list(&items, &fmt)
}
fn can_extend_match_arm_body(body: &ast::Expr) -> bool {
match body.node {
// We do not allow `if` to stay on the same line, since we could easily mistake
// `pat => if cond { ... }` and `pat if cond => { ... }`.
ast::ExprKind::If(..) | ast::ExprKind::IfLet(..) => false,
ast::ExprKind::ForLoop(..)
| ast::ExprKind::Loop(..)
| ast::ExprKind::While(..)
| ast::ExprKind::WhileLet(..)
| ast::ExprKind::Match(..)
| ast::ExprKind::Block(..)
| ast::ExprKind::Closure(..)
| ast::ExprKind::Array(..)
| ast::ExprKind::Call(..)
| ast::ExprKind::MethodCall(..)
| ast::ExprKind::Mac(..)
| ast::ExprKind::Struct(..)
| ast::ExprKind::Tup(..) => true,
ast::ExprKind::AddrOf(_, ref expr)
| ast::ExprKind::Box(ref expr)
| ast::ExprKind::Try(ref expr)
| ast::ExprKind::Unary(_, ref expr)
| ast::ExprKind::Cast(ref expr, _) => can_extend_match_arm_body(expr),
_ => false,
}
}
pub fn rewrite_literal(context: &RewriteContext, l: &ast::Lit, shape: Shape) -> Option<String> {
match l.node {
ast::LitKind::Str(_, ast::StrStyle::Cooked) => rewrite_string_lit(context, l.span, shape),
_ => wrap_str(
context.snippet(l.span).to_owned(),
context.config.max_width(),
shape,
),
}
}
fn rewrite_string_lit(context: &RewriteContext, span: Span, shape: Shape) -> Option<String> {
let string_lit = context.snippet(span);
if !context.config.format_strings() {
if string_lit
.lines()
.rev()
.skip(1)
.all(|line| line.ends_with('\\'))
{
let new_indent = shape.visual_indent(1).indent;
let indented_string_lit = String::from(
string_lit
.lines()
.map(|line| {
format!(
"{}{}",
new_indent.to_string(context.config),
line.trim_left()
)
})
.collect::<Vec<_>>()
.join("\n")
.trim_left(),
);
return wrap_str(indented_string_lit, context.config.max_width(), shape);
} else {
return wrap_str(string_lit.to_owned(), context.config.max_width(), shape);
}
}
// Remove the quote characters.
let str_lit = &string_lit[1..string_lit.len() - 1];
rewrite_string(
str_lit,
&StringFormat::new(shape.visual_indent(0), context.config),
None,
)
}
/// A list of `format!`-like macros, that take a long format string and a list of arguments to
/// format.
///
/// Organized as a list of `(&str, usize)` tuples, giving the name of the macro and the number of
/// arguments before the format string (none for `format!("format", ...)`, one for `assert!(result,
/// "format", ...)`, two for `assert_eq!(left, right, "format", ...)`).
const SPECIAL_MACRO_WHITELIST: &[(&str, usize)] = &[
// format! like macros
// From the Rust Standard Library.
("eprint!", 0),
("eprintln!", 0),
("format!", 0),
("format_args!", 0),
("print!", 0),
("println!", 0),
("panic!", 0),
("unreachable!", 0),
// From the `log` crate.
("debug!", 0),
("error!", 0),
("info!", 0),
("warn!", 0),
// write! like macros
("assert!", 1),
("debug_assert!", 1),
("write!", 1),
("writeln!", 1),
// assert_eq! like macros
("assert_eq!", 2),
("assert_ne!", 2),
("debug_assert_eq!", 2),
("debug_assert_ne!", 2),
];
pub fn rewrite_call(
context: &RewriteContext,
callee: &str,
args: &[ptr::P<ast::Expr>],
span: Span,
shape: Shape,
) -> Option<String> {
let force_trailing_comma = if context.inside_macro {
span_ends_with_comma(context, span)
} else {
false
};
rewrite_call_inner(
context,
callee,
&ptr_vec_to_ref_vec(args),
span,
shape,
context.config.width_heuristics().fn_call_width,
force_trailing_comma,
)
}
pub fn rewrite_call_inner<'a, T>(
context: &RewriteContext,
callee_str: &str,
args: &[&T],
span: Span,
shape: Shape,
args_max_width: usize,
force_trailing_comma: bool,
) -> Option<String>
where
T: Rewrite + Spanned + ToExpr + 'a,
{
// 2 = `( `, 1 = `(`
let paren_overhead = if context.config.spaces_within_parens_and_brackets() {
2
} else {
1
};
let used_width = extra_offset(callee_str, shape);
let one_line_width = shape
.width
.checked_sub(used_width + 2 * paren_overhead)
.unwrap_or(0);
// 1 = "(" or ")"
let one_line_shape = shape
.offset_left(last_line_width(callee_str) + 1)
.and_then(|shape| shape.sub_width(1))
.unwrap_or(Shape { width: 0, ..shape });
let nested_shape = shape_from_indent_style(
context,
shape,
used_width + 2 * paren_overhead,
used_width + paren_overhead,
)?;
let span_lo = context.snippet_provider.span_after(span, "(");
let args_span = mk_sp(span_lo, span.hi());
let (extendable, list_str) = rewrite_call_args(
context,
args,
args_span,
one_line_shape,
nested_shape,
one_line_width,
args_max_width,
force_trailing_comma,
callee_str,
)?;
if !context.use_block_indent() && need_block_indent(&list_str, nested_shape) && !extendable {
let mut new_context = context.clone();
new_context.use_block = true;
return rewrite_call_inner(
&new_context,
callee_str,
args,
span,
shape,
args_max_width,
force_trailing_comma,
);
}
let args_shape = Shape {
width: shape
.width
.checked_sub(last_line_width(callee_str))
.unwrap_or(0),
..shape
};
Some(format!(
"{}{}",
callee_str,
wrap_args_with_parens(context, &list_str, extendable, args_shape, nested_shape)
))
}
fn need_block_indent(s: &str, shape: Shape) -> bool {
s.lines().skip(1).any(|s| {
s.find(|c| !char::is_whitespace(c))
.map_or(false, |w| w + 1 < shape.indent.width())
})
}
fn rewrite_call_args<'a, T>(
context: &RewriteContext,
args: &[&T],
span: Span,
one_line_shape: Shape,
nested_shape: Shape,
one_line_width: usize,
args_max_width: usize,
force_trailing_comma: bool,
callee_str: &str,
) -> Option<(bool, String)>
where
T: Rewrite + Spanned + ToExpr + 'a,
{
let items = itemize_list(
context.snippet_provider,
args.iter(),
")",
",",
|item| item.span().lo(),
|item| item.span().hi(),
|item| item.rewrite(context, nested_shape),
span.lo(),
span.hi(),
true,
);
let mut item_vec: Vec<_> = items.collect();
// Try letting the last argument overflow to the next line with block
// indentation. If its first line fits on one line with the other arguments,
// we format the function arguments horizontally.
let tactic = try_overflow_last_arg(
context,
&mut item_vec,
&args[..],
one_line_shape,
nested_shape,
one_line_width,
args_max_width,
callee_str,
);
let fmt = ListFormatting {
tactic,
separator: ",",
trailing_separator: if force_trailing_comma {
SeparatorTactic::Always
} else if context.inside_macro || !context.use_block_indent() {
SeparatorTactic::Never
} else {
context.config.trailing_comma()
},
separator_place: SeparatorPlace::Back,
shape: nested_shape,
ends_with_newline: context.use_block_indent() && tactic == DefinitiveListTactic::Vertical,
preserve_newline: false,
config: context.config,
};
write_list(&item_vec, &fmt)
.map(|args_str| (tactic == DefinitiveListTactic::Horizontal, args_str))
}
fn try_overflow_last_arg<'a, T>(
context: &RewriteContext,
item_vec: &mut Vec<ListItem>,
args: &[&T],
one_line_shape: Shape,
nested_shape: Shape,
one_line_width: usize,
args_max_width: usize,
callee_str: &str,
) -> DefinitiveListTactic
where
T: Rewrite + Spanned + ToExpr + 'a,
{
// 1 = "("
let combine_arg_with_callee =
callee_str.len() + 1 <= context.config.tab_spaces() && args.len() == 1;
let overflow_last = combine_arg_with_callee || can_be_overflowed(context, args);
// Replace the last item with its first line to see if it fits with
// first arguments.
let placeholder = if overflow_last {
let mut context = context.clone();
if !combine_arg_with_callee {
if let Some(expr) = args[args.len() - 1].to_expr() {
if let ast::ExprKind::MethodCall(..) = expr.node {
context.force_one_line_chain = true;
}
}
}
last_arg_shape(args, item_vec, one_line_shape, args_max_width).and_then(|arg_shape| {
rewrite_last_arg_with_overflow(&context, args, &mut item_vec[args.len() - 1], arg_shape)
})
} else {
None
};
let mut tactic = definitive_tactic(
&*item_vec,
ListTactic::LimitedHorizontalVertical(args_max_width),
Separator::Comma,
one_line_width,
);
// Replace the stub with the full overflowing last argument if the rewrite
// succeeded and its first line fits with the other arguments.
match (overflow_last, tactic, placeholder) {
(true, DefinitiveListTactic::Horizontal, Some(ref overflowed)) if args.len() == 1 => {
// When we are rewriting a nested function call, we restrict the
// bugdet for the inner function to avoid them being deeply nested.
// However, when the inner function has a prefix or a suffix
// (e.g. `foo() as u32`), this budget reduction may produce poorly
// formatted code, where a prefix or a suffix being left on its own
// line. Here we explicitlly check those cases.
if count_newlines(overflowed) == 1 {
let rw = args.last()
.and_then(|last_arg| last_arg.rewrite(context, nested_shape));
let no_newline = rw.as_ref().map_or(false, |s| !s.contains('\n'));
if no_newline {
item_vec[args.len() - 1].item = rw;
} else {
item_vec[args.len() - 1].item = Some(overflowed.to_owned());
}
} else {
item_vec[args.len() - 1].item = Some(overflowed.to_owned());
}
}
(true, DefinitiveListTactic::Horizontal, placeholder @ Some(..)) => {
item_vec[args.len() - 1].item = placeholder;
}
_ if args.len() >= 1 => {
item_vec[args.len() - 1].item = args.last()
.and_then(|last_arg| last_arg.rewrite(context, nested_shape));
let default_tactic = || {
definitive_tactic(
&*item_vec,
ListTactic::LimitedHorizontalVertical(args_max_width),
Separator::Comma,
one_line_width,
)
};
// Use horizontal layout for a function with a single argument as long as
// everything fits in a single line.
if args.len() == 1
&& args_max_width != 0 // Vertical layout is forced.
&& !item_vec[0].has_comment()
&& !item_vec[0].inner_as_ref().contains('\n')
&& ::lists::total_item_width(&item_vec[0]) <= one_line_width
{
tactic = DefinitiveListTactic::Horizontal;
} else {
tactic = default_tactic();
if tactic == DefinitiveListTactic::Vertical {
if let Some((all_simple, num_args_before)) =
maybe_get_args_offset(callee_str, args)
{
let one_line = all_simple
&& definitive_tactic(
&item_vec[..num_args_before],
ListTactic::HorizontalVertical,
Separator::Comma,
nested_shape.width,
) == DefinitiveListTactic::Horizontal
&& definitive_tactic(
&item_vec[num_args_before + 1..],
ListTactic::HorizontalVertical,
Separator::Comma,
nested_shape.width,
) == DefinitiveListTactic::Horizontal;
if one_line {
tactic = DefinitiveListTactic::SpecialMacro(num_args_before);
};
}
}
}
}
_ => (),
}
tactic
}
fn is_simple_arg(expr: &ast::Expr) -> bool {
match expr.node {
ast::ExprKind::Lit(..) => true,
ast::ExprKind::Path(ref qself, ref path) => qself.is_none() && path.segments.len() <= 1,
ast::ExprKind::AddrOf(_, ref expr)
| ast::ExprKind::Box(ref expr)
| ast::ExprKind::Cast(ref expr, _)
| ast::ExprKind::Field(ref expr, _)
| ast::ExprKind::Try(ref expr)
| ast::ExprKind::TupField(ref expr, _)
| ast::ExprKind::Unary(_, ref expr) => is_simple_arg(expr),
ast::ExprKind::Index(ref lhs, ref rhs) | ast::ExprKind::Repeat(ref lhs, ref rhs) => {
is_simple_arg(lhs) && is_simple_arg(rhs)
}
_ => false,
}
}
fn is_every_args_simple<T: ToExpr>(lists: &[&T]) -> bool {
lists
.iter()
.all(|arg| arg.to_expr().map_or(false, is_simple_arg))
}
/// In case special-case style is required, returns an offset from which we start horizontal layout.
fn maybe_get_args_offset<T: ToExpr>(callee_str: &str, args: &[&T]) -> Option<(bool, usize)> {
if let Some(&(_, num_args_before)) = SPECIAL_MACRO_WHITELIST
.iter()
.find(|&&(s, _)| s == callee_str)
{
let all_simple = args.len() > num_args_before && is_every_args_simple(args);
Some((all_simple, num_args_before))
} else {
None
}
}
/// Returns a shape for the last argument which is going to be overflowed.
fn last_arg_shape<T>(
lists: &[&T],
items: &[ListItem],
shape: Shape,
args_max_width: usize,
) -> Option<Shape>
where
T: Rewrite + Spanned + ToExpr,
{
let is_nested_call = lists
.iter()
.next()
.and_then(|item| item.to_expr())
.map_or(false, is_nested_call);
if items.len() == 1 && !is_nested_call {
return Some(shape);
}
let offset = items.iter().rev().skip(1).fold(0, |acc, i| {
// 2 = ", "
acc + 2 + i.inner_as_ref().len()
});
Shape {
width: min(args_max_width, shape.width),
..shape
}.offset_left(offset)
}
fn rewrite_last_arg_with_overflow<'a, T>(
context: &RewriteContext,
args: &[&T],
last_item: &mut ListItem,
shape: Shape,
) -> Option<String>
where
T: Rewrite + Spanned + ToExpr + 'a,
{
let last_arg = args[args.len() - 1];
let rewrite = if let Some(expr) = last_arg.to_expr() {
match expr.node {
// When overflowing the closure which consists of a single control flow expression,
// force to use block if its condition uses multi line.
ast::ExprKind::Closure(..) => {
// If the argument consists of multiple closures, we do not overflow
// the last closure.
if closures::args_have_many_closure(args) {
None
} else {
closures::rewrite_last_closure(context, expr, shape)
}
}
_ => expr.rewrite(context, shape),
}
} else {
last_arg.rewrite(context, shape)
};
if let Some(rewrite) = rewrite {
let rewrite_first_line = Some(rewrite[..first_line_width(&rewrite)].to_owned());
last_item.item = rewrite_first_line;
Some(rewrite)
} else {
None
}
}
fn can_be_overflowed<'a, T>(context: &RewriteContext, args: &[&T]) -> bool
where
T: Rewrite + Spanned + ToExpr + 'a,
{
args.last()
.map_or(false, |x| x.can_be_overflowed(context, args.len()))
}
pub fn can_be_overflowed_expr(context: &RewriteContext, expr: &ast::Expr, args_len: usize) -> bool {
match expr.node {
ast::ExprKind::Match(..) => {
(context.use_block_indent() && args_len == 1)
|| (context.config.indent_style() == IndentStyle::Visual && args_len > 1)
}
ast::ExprKind::If(..)
| ast::ExprKind::IfLet(..)
| ast::ExprKind::ForLoop(..)
| ast::ExprKind::Loop(..)
| ast::ExprKind::While(..)
| ast::ExprKind::WhileLet(..) => {
context.config.combine_control_expr() && context.use_block_indent() && args_len == 1
}
ast::ExprKind::Block(..) | ast::ExprKind::Closure(..) => {
context.use_block_indent()
|| context.config.indent_style() == IndentStyle::Visual && args_len > 1
}
ast::ExprKind::Array(..)
| ast::ExprKind::Call(..)
| ast::ExprKind::Mac(..)
| ast::ExprKind::MethodCall(..)
| ast::ExprKind::Struct(..)
| ast::ExprKind::Tup(..) => context.use_block_indent() && args_len == 1,
ast::ExprKind::AddrOf(_, ref expr)
| ast::ExprKind::Box(ref expr)
| ast::ExprKind::Try(ref expr)
| ast::ExprKind::Unary(_, ref expr)
| ast::ExprKind::Cast(ref expr, _) => can_be_overflowed_expr(context, expr, args_len),
_ => false,
}
}
fn is_nested_call(expr: &ast::Expr) -> bool {
match expr.node {
ast::ExprKind::Call(..) | ast::ExprKind::Mac(..) => true,
ast::ExprKind::AddrOf(_, ref expr)
| ast::ExprKind::Box(ref expr)
| ast::ExprKind::Try(ref expr)
| ast::ExprKind::Unary(_, ref expr)
| ast::ExprKind::Cast(ref expr, _) => is_nested_call(expr),
_ => false,
}
}
pub fn wrap_args_with_parens(
context: &RewriteContext,
args_str: &str,
is_extendable: bool,
shape: Shape,
nested_shape: Shape,
) -> String {
let paren_overhead = paren_overhead(context);
let fits_one_line = args_str.len() + paren_overhead <= shape.width;
let extend_width = if args_str.is_empty() {
paren_overhead
} else {
paren_overhead / 2
};
if !context.use_block_indent()
|| (context.inside_macro && !args_str.contains('\n') && fits_one_line)
|| (is_extendable && extend_width <= shape.width)
{
let mut result = String::with_capacity(args_str.len() + 4);
if context.config.spaces_within_parens_and_brackets() && !args_str.is_empty() {
result.push_str("( ");
result.push_str(args_str);
result.push_str(" )");
} else {
result.push_str("(");
result.push_str(args_str);
result.push_str(")");
}
result
} else {
let nested_indent_str = nested_shape.indent.to_string_with_newline(context.config);
let indent_str = shape.block().indent.to_string_with_newline(context.config);
let mut result =
String::with_capacity(args_str.len() + 2 + indent_str.len() + nested_indent_str.len());
result.push_str("(");
if !args_str.is_empty() {
result.push_str(&nested_indent_str);
result.push_str(args_str);
}
result.push_str(&indent_str);
result.push_str(")");
result
}
}
/// Return true if a function call or a method call represented by the given span ends with a
/// trailing comma. This function is used when rewriting macro, as adding or removing a trailing
/// comma from macro can potentially break the code.
fn span_ends_with_comma(context: &RewriteContext, span: Span) -> bool {
let mut result: bool = Default::default();
let mut prev_char: char = Default::default();
for (kind, c) in CharClasses::new(context.snippet(span).chars()) {
match c {
_ if kind.is_comment() || c.is_whitespace() => continue,
')' | '}' => result = result && prev_char != c,
',' => result = true,
_ => result = false,
}
prev_char = c;
}
result
}
fn rewrite_paren(
context: &RewriteContext,
mut subexpr: &ast::Expr,
shape: Shape,
mut span: Span,
) -> Option<String> {
debug!("rewrite_paren, shape: {:?}", shape);
// Extract comments within parens.
let mut pre_comment;
let mut post_comment;
loop {
// 1 = "(" or ")"
let pre_span = mk_sp(span.lo() + BytePos(1), subexpr.span.lo());
let post_span = mk_sp(subexpr.span.hi(), span.hi() - BytePos(1));
pre_comment = rewrite_missing_comment(pre_span, shape, context)?;
post_comment = rewrite_missing_comment(post_span, shape, context)?;
// Remove nested parens if there are no comments.
if let ast::ExprKind::Paren(ref subsubexpr) = subexpr.node {
if pre_comment.is_empty() && post_comment.is_empty() {
span = subexpr.span;
subexpr = subsubexpr;
continue;
}
}
break;
}
let total_paren_overhead = paren_overhead(context);
let paren_overhead = total_paren_overhead / 2;
let sub_shape = shape
.offset_left(paren_overhead)
.and_then(|s| s.sub_width(paren_overhead))?;
let paren_wrapper = |s: &str| {
if context.config.spaces_within_parens_and_brackets() && !s.is_empty() {
format!("( {}{}{} )", pre_comment, s, post_comment)
} else {
format!("({}{}{})", pre_comment, s, post_comment)
}
};
let subexpr_str = subexpr.rewrite(context, sub_shape)?;
debug!("rewrite_paren, subexpr_str: `{:?}`", subexpr_str);
if subexpr_str.contains('\n')
|| first_line_width(&subexpr_str) + total_paren_overhead <= shape.width
{
Some(paren_wrapper(&subexpr_str))
} else {
None
}
}
fn rewrite_index(
expr: &ast::Expr,
index: &ast::Expr,
context: &RewriteContext,
shape: Shape,
) -> Option<String> {
let expr_str = expr.rewrite(context, shape)?;
let (lbr, rbr) = if context.config.spaces_within_parens_and_brackets() {
("[ ", " ]")
} else {
("[", "]")
};
let offset = last_line_width(&expr_str) + lbr.len();
let rhs_overhead = shape.rhs_overhead(context.config);
let index_shape = if expr_str.contains('\n') {
Shape::legacy(context.config.max_width(), shape.indent)
.offset_left(offset)
.and_then(|shape| shape.sub_width(rbr.len() + rhs_overhead))
} else {
shape.visual_indent(offset).sub_width(offset + rbr.len())
};
let orig_index_rw = index_shape.and_then(|s| index.rewrite(context, s));
// Return if index fits in a single line.
match orig_index_rw {
Some(ref index_str) if !index_str.contains('\n') => {
return Some(format!("{}{}{}{}", expr_str, lbr, index_str, rbr));
}
_ => (),
}
// Try putting index on the next line and see if it fits in a single line.
let indent = shape.indent.block_indent(context.config);
let index_shape = Shape::indented(indent, context.config).offset_left(lbr.len())?;
let index_shape = index_shape.sub_width(rbr.len() + rhs_overhead)?;
let new_index_rw = index.rewrite(context, index_shape);
match (orig_index_rw, new_index_rw) {
(_, Some(ref new_index_str)) if !new_index_str.contains('\n') => Some(format!(
"{}{}{}{}{}",
expr_str,
indent.to_string_with_newline(context.config),
lbr,
new_index_str,
rbr
)),
(None, Some(ref new_index_str)) => Some(format!(
"{}{}{}{}{}",
expr_str,
indent.to_string_with_newline(context.config),
lbr,
new_index_str,
rbr
)),
(Some(ref index_str), _) => Some(format!("{}{}{}{}", expr_str, lbr, index_str, rbr)),
_ => None,
}
}
fn struct_lit_can_be_aligned(fields: &[ast::Field], base: &Option<&ast::Expr>) -> bool {
if base.is_some() {
return false;
}
fields.iter().all(|field| !field.is_shorthand)
}
fn rewrite_struct_lit<'a>(
context: &RewriteContext,
path: &ast::Path,
fields: &'a [ast::Field],
base: Option<&'a ast::Expr>,
span: Span,
shape: Shape,
) -> Option<String> {
debug!("rewrite_struct_lit: shape {:?}", shape);
enum StructLitField<'a> {
Regular(&'a ast::Field),
Base(&'a ast::Expr),
}
// 2 = " {".len()
let path_shape = shape.sub_width(2)?;
let path_str = rewrite_path(context, PathContext::Expr, None, path, path_shape)?;
if fields.is_empty() && base.is_none() {
return Some(format!("{} {{}}", path_str));
}
// Foo { a: Foo } - indent is +3, width is -5.
let (h_shape, v_shape) = struct_lit_shape(shape, context, path_str.len() + 3, 2)?;
let one_line_width = h_shape.map_or(0, |shape| shape.width);
let body_lo = context.snippet_provider.span_after(span, "{");
let fields_str = if struct_lit_can_be_aligned(fields, &base)
&& context.config.struct_field_align_threshold() > 0
{
rewrite_with_alignment(
fields,
context,
shape,
mk_sp(body_lo, span.hi()),
one_line_width,
)?
} else {
let field_iter = fields
.into_iter()
.map(StructLitField::Regular)
.chain(base.into_iter().map(StructLitField::Base));
let span_lo = |item: &StructLitField| match *item {
StructLitField::Regular(field) => field.span().lo(),
StructLitField::Base(expr) => {
let last_field_hi = fields.last().map_or(span.lo(), |field| field.span.hi());
let snippet = context.snippet(mk_sp(last_field_hi, expr.span.lo()));
let pos = snippet.find_uncommented("..").unwrap();
last_field_hi + BytePos(pos as u32)
}
};
let span_hi = |item: &StructLitField| match *item {
StructLitField::Regular(field) => field.span().hi(),
StructLitField::Base(expr) => expr.span.hi(),
};
let rewrite = |item: &StructLitField| match *item {
StructLitField::Regular(field) => {
// The 1 taken from the v_budget is for the comma.
rewrite_field(context, field, v_shape.sub_width(1)?, 0)
}
StructLitField::Base(expr) => {
// 2 = ..
expr.rewrite(context, v_shape.offset_left(2)?)
.map(|s| format!("..{}", s))
}
};
let items = itemize_list(
context.snippet_provider,
field_iter,
"}",
",",
span_lo,
span_hi,
rewrite,
body_lo,
span.hi(),
false,
);
let item_vec = items.collect::<Vec<_>>();
let tactic = struct_lit_tactic(h_shape, context, &item_vec);
let nested_shape = shape_for_tactic(tactic, h_shape, v_shape);
let ends_with_comma = span_ends_with_comma(context, span);
let force_no_trailing_comma = if context.inside_macro && !ends_with_comma {
true
} else {
false
};
let fmt = struct_lit_formatting(
nested_shape,
tactic,
context,
force_no_trailing_comma || base.is_some(),
);
write_list(&item_vec, &fmt)?
};
let fields_str = wrap_struct_field(context, &fields_str, shape, v_shape, one_line_width);
Some(format!("{} {{{}}}", path_str, fields_str))
// FIXME if context.config.indent_style() == Visual, but we run out
// of space, we should fall back to BlockIndent.
}
pub fn wrap_struct_field(
context: &RewriteContext,
fields_str: &str,
shape: Shape,
nested_shape: Shape,
one_line_width: usize,
) -> String {
if context.config.indent_style() == IndentStyle::Block
&& (fields_str.contains('\n') || !context.config.struct_lit_single_line()
|| fields_str.len() > one_line_width)
{
format!(
"{}{}{}",
nested_shape.indent.to_string_with_newline(context.config),
fields_str,
shape.indent.to_string_with_newline(context.config)
)
} else {
// One liner or visual indent.
format!(" {} ", fields_str)
}
}
pub fn struct_lit_field_separator(config: &Config) -> &str {
colon_spaces(config.space_before_colon(), config.space_after_colon())
}
pub fn rewrite_field(
context: &RewriteContext,
field: &ast::Field,
shape: Shape,
prefix_max_width: usize,
) -> Option<String> {
if contains_skip(&field.attrs) {
return Some(context.snippet(field.span()).to_owned());
}
let mut attrs_str = field.attrs.rewrite(context, shape)?;
if !attrs_str.is_empty() {
attrs_str.push_str(&shape.indent.to_string_with_newline(context.config));
};
let name = field.ident.node.to_string();
if field.is_shorthand {
Some(attrs_str + &name)
} else {
let mut separator = String::from(struct_lit_field_separator(context.config));
for _ in 0..prefix_max_width.checked_sub(name.len()).unwrap_or(0) {
separator.push(' ');
}
let overhead = name.len() + separator.len();
let expr_shape = shape.offset_left(overhead)?;
let expr = field.expr.rewrite(context, expr_shape);
match expr {
Some(ref e) if e.as_str() == name && context.config.use_field_init_shorthand() => {
Some(attrs_str + &name)
}
Some(e) => Some(format!("{}{}{}{}", attrs_str, name, separator, e)),
None => {
let expr_offset = shape.indent.block_indent(context.config);
let expr = field
.expr
.rewrite(context, Shape::indented(expr_offset, context.config));
expr.map(|s| {
format!(
"{}{}:\n{}{}",
attrs_str,
name,
expr_offset.to_string(context.config),
s
)
})
}
}
}
}
fn shape_from_indent_style(
context: &RewriteContext,
shape: Shape,
overhead: usize,
offset: usize,
) -> Option<Shape> {
if context.use_block_indent() {
// 1 = ","
shape
.block()
.block_indent(context.config.tab_spaces())
.with_max_width(context.config)
.sub_width(1)
} else {
shape.visual_indent(offset).sub_width(overhead)
}
}
fn rewrite_tuple_in_visual_indent_style<'a, T>(
context: &RewriteContext,
items: &[&T],
span: Span,
shape: Shape,
) -> Option<String>
where
T: Rewrite + Spanned + ToExpr + 'a,
{
let mut items = items.iter();
// In case of length 1, need a trailing comma
debug!("rewrite_tuple_in_visual_indent_style {:?}", shape);
if items.len() == 1 {
// 3 = "(" + ",)"
let nested_shape = shape.sub_width(3)?.visual_indent(1);
return items
.next()
.unwrap()
.rewrite(context, nested_shape)
.map(|s| {
if context.config.spaces_within_parens_and_brackets() {
format!("( {}, )", s)
} else {
format!("({},)", s)
}
});
}
let list_lo = context.snippet_provider.span_after(span, "(");
let nested_shape = shape.sub_width(2)?.visual_indent(1);
let items = itemize_list(
context.snippet_provider,
items,
")",
",",
|item| item.span().lo(),
|item| item.span().hi(),
|item| item.rewrite(context, nested_shape),
list_lo,
span.hi() - BytePos(1),
false,
);
let item_vec: Vec<_> = items.collect();
let tactic = definitive_tactic(
&item_vec,
ListTactic::HorizontalVertical,
Separator::Comma,
nested_shape.width,
);
let fmt = ListFormatting {
tactic,
separator: ",",
trailing_separator: SeparatorTactic::Never,
separator_place: SeparatorPlace::Back,
shape,
ends_with_newline: false,
preserve_newline: false,
config: context.config,
};
let list_str = write_list(&item_vec, &fmt)?;
if context.config.spaces_within_parens_and_brackets() && !list_str.is_empty() {
Some(format!("( {} )", list_str))
} else {
Some(format!("({})", list_str))
}
}
pub fn rewrite_tuple<'a, T>(
context: &RewriteContext,
items: &[&T],
span: Span,
shape: Shape,
) -> Option<String>
where
T: Rewrite + Spanned + ToExpr + 'a,
{
debug!("rewrite_tuple {:?}", shape);
if context.use_block_indent() {
// We use the same rule as function calls for rewriting tuples.
let force_trailing_comma = if context.inside_macro {
span_ends_with_comma(context, span)
} else {
items.len() == 1
};
rewrite_call_inner(
context,
&String::new(),
items,
span,
shape,
context.config.width_heuristics().fn_call_width,
force_trailing_comma,
)
} else {
rewrite_tuple_in_visual_indent_style(context, items, span, shape)
}
}
pub fn rewrite_unary_prefix<R: Rewrite>(
context: &RewriteContext,
prefix: &str,
rewrite: &R,
shape: Shape,
) -> Option<String> {
rewrite
.rewrite(context, shape.offset_left(prefix.len())?)
.map(|r| format!("{}{}", prefix, r))
}
// FIXME: this is probably not correct for multi-line Rewrites. we should
// subtract suffix.len() from the last line budget, not the first!
pub fn rewrite_unary_suffix<R: Rewrite>(
context: &RewriteContext,
suffix: &str,
rewrite: &R,
shape: Shape,
) -> Option<String> {
rewrite
.rewrite(context, shape.sub_width(suffix.len())?)
.map(|mut r| {
r.push_str(suffix);
r
})
}
fn rewrite_unary_op(
context: &RewriteContext,
op: &ast::UnOp,
expr: &ast::Expr,
shape: Shape,
) -> Option<String> {
// For some reason, an UnOp is not spanned like BinOp!
let operator_str = match *op {
ast::UnOp::Deref => "*",
ast::UnOp::Not => "!",
ast::UnOp::Neg => "-",
};
rewrite_unary_prefix(context, operator_str, expr, shape)
}
fn rewrite_assignment(
context: &RewriteContext,
lhs: &ast::Expr,
rhs: &ast::Expr,
op: Option<&ast::BinOp>,
shape: Shape,
) -> Option<String> {
let operator_str = match op {
Some(op) => context.snippet(op.span),
None => "=",
};
// 1 = space between lhs and operator.
let lhs_shape = shape.sub_width(operator_str.len() + 1)?;
let lhs_str = format!("{} {}", lhs.rewrite(context, lhs_shape)?, operator_str);
rewrite_assign_rhs(context, lhs_str, rhs, shape)
}
// The left hand side must contain everything up to, and including, the
// assignment operator.
pub fn rewrite_assign_rhs<S: Into<String>, R: Rewrite>(
context: &RewriteContext,
lhs: S,
ex: &R,
shape: Shape,
) -> Option<String> {
let lhs = lhs.into();
let last_line_width = last_line_width(&lhs)
.checked_sub(if lhs.contains('\n') {
shape.indent.width()
} else {
0
})
.unwrap_or(0);
// 1 = space between operator and rhs.
let orig_shape = shape.offset_left(last_line_width + 1).unwrap_or(Shape {
width: 0,
offset: shape.offset + last_line_width + 1,
..shape
});
let rhs = choose_rhs(context, ex, orig_shape, ex.rewrite(context, orig_shape))?;
Some(lhs + &rhs)
}
pub fn choose_rhs<R: Rewrite>(
context: &RewriteContext,
expr: &R,
shape: Shape,
orig_rhs: Option<String>,
) -> Option<String> {
match orig_rhs {
Some(ref new_str) if !new_str.contains('\n') && new_str.len() <= shape.width => {
Some(format!(" {}", new_str))
}
_ => {
// Expression did not fit on the same line as the identifier.
// Try splitting the line and see if that works better.
let new_shape =
Shape::indented(shape.indent.block_indent(context.config), context.config)
.sub_width(shape.rhs_overhead(context.config))?;
let new_rhs = expr.rewrite(context, new_shape);
let new_indent_str = &new_shape.indent.to_string_with_newline(context.config);
match (orig_rhs, new_rhs) {
(Some(ref orig_rhs), Some(ref new_rhs))
if wrap_str(new_rhs.clone(), context.config.max_width(), new_shape)
.is_none() =>
{
Some(format!(" {}", orig_rhs))
}
(Some(ref orig_rhs), Some(ref new_rhs)) if prefer_next_line(orig_rhs, new_rhs) => {
Some(format!("{}{}", new_indent_str, new_rhs))
}
(None, Some(ref new_rhs)) => Some(format!("{}{}", new_indent_str, new_rhs)),
(None, None) => None,
(Some(ref orig_rhs), _) => Some(format!(" {}", orig_rhs)),
}
}
}
}
fn prefer_next_line(orig_rhs: &str, next_line_rhs: &str) -> bool {
!next_line_rhs.contains('\n') || count_newlines(orig_rhs) > count_newlines(next_line_rhs) + 1
}
fn rewrite_expr_addrof(
context: &RewriteContext,
mutability: ast::Mutability,
expr: &ast::Expr,
shape: Shape,
) -> Option<String> {
let operator_str = match mutability {
ast::Mutability::Immutable => "&",
ast::Mutability::Mutable => "&mut ",
};
rewrite_unary_prefix(context, operator_str, expr, shape)
}
pub trait ToExpr {
fn to_expr(&self) -> Option<&ast::Expr>;
fn can_be_overflowed(&self, context: &RewriteContext, len: usize) -> bool;
}
impl ToExpr for ast::Expr {
fn to_expr(&self) -> Option<&ast::Expr> {
Some(self)
}
fn can_be_overflowed(&self, context: &RewriteContext, len: usize) -> bool {
can_be_overflowed_expr(context, self, len)
}
}
impl ToExpr for ast::Ty {
fn to_expr(&self) -> Option<&ast::Expr> {
None
}
fn can_be_overflowed(&self, context: &RewriteContext, len: usize) -> bool {
can_be_overflowed_type(context, self, len)
}
}
impl<'a> ToExpr for TuplePatField<'a> {
fn to_expr(&self) -> Option<&ast::Expr> {
None
}
fn can_be_overflowed(&self, context: &RewriteContext, len: usize) -> bool {
can_be_overflowed_pat(context, self, len)
}
}
impl<'a> ToExpr for ast::StructField {
fn to_expr(&self) -> Option<&ast::Expr> {
None
}
fn can_be_overflowed(&self, _: &RewriteContext, _: usize) -> bool {
false
}
}
impl<'a> ToExpr for MacroArg {
fn to_expr(&self) -> Option<&ast::Expr> {
match *self {
MacroArg::Expr(ref expr) => Some(expr),
_ => None,
}
}
fn can_be_overflowed(&self, context: &RewriteContext, len: usize) -> bool {
match *self {
MacroArg::Expr(ref expr) => can_be_overflowed_expr(context, expr, len),
MacroArg::Ty(ref ty) => can_be_overflowed_type(context, ty, len),
MacroArg::Pat(..) => false,
}
}
}
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