rust/src/patterns.rs

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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 Shape;
use codemap::SpanUtils;
use config::{IndentStyle, MultilineStyle};
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use rewrite::{Rewrite, RewriteContext};
use utils::{wrap_str, format_mutability};
use lists::{DefinitiveListTactic, SeparatorTactic, format_item_list, itemize_list, ListItem,
struct_lit_shape, struct_lit_tactic, shape_for_tactic, struct_lit_formatting,
write_list};
use expr::{rewrite_unary_prefix, rewrite_pair};
use types::{rewrite_path, PathContext};
use super::Spanned;
use comment::FindUncommented;
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use syntax::ast::{self, BindingMode, Pat, PatKind, FieldPat, RangeEnd};
use syntax::ptr;
use syntax::codemap::{self, BytePos, Span};
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impl Rewrite for Pat {
fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
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match self.node {
PatKind::Box(ref pat) => rewrite_unary_prefix(context, "box ", &**pat, shape),
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PatKind::Ident(binding_mode, ident, ref sub_pat) => {
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let (prefix, mutability) = match binding_mode {
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BindingMode::ByRef(mutability) => ("ref ", mutability),
BindingMode::ByValue(mutability) => ("", mutability),
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};
let mut_infix = format_mutability(mutability);
let id_str = ident.node.to_string();
let sub_pat = match *sub_pat {
Some(ref p) => {
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// 3 - ` @ `.
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let width =
try_opt!(shape.width.checked_sub(prefix.len() + mut_infix.len() +
id_str.len() +
3));
format!(" @ {}",
try_opt!(p.rewrite(context, Shape::legacy(width, shape.indent))))
}
None => "".to_owned(),
};
let result = format!("{}{}{}{}", prefix, mut_infix, id_str, sub_pat);
wrap_str(result, context.config.max_width(), shape)
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}
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PatKind::Wild => {
if 1 <= shape.width {
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Some("_".to_owned())
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} else {
None
}
}
PatKind::Range(ref lhs, ref rhs, ref end_kind) => {
match *end_kind {
RangeEnd::Included => {
rewrite_pair(&**lhs, &**rhs, "", "...", "", context, shape)
}
RangeEnd::Excluded => {
rewrite_pair(&**lhs, &**rhs, "", "..", "", context, shape)
}
}
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}
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PatKind::Ref(ref pat, mutability) => {
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let prefix = format!("&{}", format_mutability(mutability));
rewrite_unary_prefix(context, &prefix, &**pat, shape)
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}
PatKind::Tuple(ref items, dotdot_pos) => {
rewrite_tuple_pat(items, dotdot_pos, None, self.span, context, shape)
}
PatKind::Path(ref q_self, ref path) => {
rewrite_path(context, PathContext::Expr, q_self.as_ref(), path, shape)
}
PatKind::TupleStruct(ref path, ref pat_vec, dotdot_pos) => {
let path_str =
try_opt!(rewrite_path(context, PathContext::Expr, None, path, shape));
rewrite_tuple_pat(pat_vec,
dotdot_pos,
Some(path_str),
self.span,
context,
shape)
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}
PatKind::Lit(ref expr) => expr.rewrite(context, shape),
PatKind::Slice(ref prefix, ref slice_pat, ref suffix) => {
// Rewrite all the sub-patterns.
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let prefix = prefix.iter().map(|p| p.rewrite(context, shape));
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let slice_pat =
slice_pat
.as_ref()
.map(|p| Some(format!("{}..", try_opt!(p.rewrite(context, shape)))));
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let suffix = suffix.iter().map(|p| p.rewrite(context, shape));
// Munge them together.
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let pats: Option<Vec<String>> =
prefix.chain(slice_pat.into_iter()).chain(suffix).collect();
// Check that all the rewrites succeeded, and if not return None.
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let pats = try_opt!(pats);
// Unwrap all the sub-strings and join them with commas.
let result = if context.config.spaces_within_square_brackets() {
format!("[ {} ]", pats.join(", "))
} else {
format!("[{}]", pats.join(", "))
};
wrap_str(result, context.config.max_width(), shape)
}
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PatKind::Struct(ref path, ref fields, elipses) => {
rewrite_struct_pat(path, fields, elipses, self.span, context, shape)
}
// FIXME(#819) format pattern macros.
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PatKind::Mac(..) => {
wrap_str(context.snippet(self.span),
context.config.max_width(),
shape)
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}
}
}
}
fn rewrite_struct_pat(path: &ast::Path,
fields: &[codemap::Spanned<ast::FieldPat>],
elipses: bool,
span: Span,
context: &RewriteContext,
shape: Shape)
-> Option<String> {
// 2 = ` {`
let path_shape = try_opt!(shape.sub_width(2));
let path_str = try_opt!(rewrite_path(context, PathContext::Expr, None, path, path_shape));
if fields.len() == 0 && !elipses {
return Some(format!("{} {{}}", path_str));
}
let (elipses_str, terminator) = if elipses { (", ..", "..") } else { ("", "}") };
// 3 = ` { `, 2 = ` }`.
let (h_shape, v_shape) =
try_opt!(struct_lit_shape(shape, context, path_str.len() + 3, elipses_str.len() + 2));
let items = itemize_list(context.codemap,
fields.iter(),
terminator,
|f| f.span.lo,
|f| f.span.hi,
|f| f.node.rewrite(context, v_shape),
context.codemap.span_after(span, "{"),
span.hi);
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 fmt = struct_lit_formatting(nested_shape, tactic, context, false);
let mut fields_str = try_opt!(write_list(&item_vec, &fmt));
if elipses {
if fields_str.contains('\n') {
// Add a missing trailing comma.
if fmt.trailing_separator == SeparatorTactic::Never {
fields_str.push_str(",");
}
fields_str.push_str("\n");
fields_str.push_str(&nested_shape.indent.to_string(context.config));
fields_str.push_str("..");
} else {
if !fields_str.is_empty() {
// there are preceeding struct fields being matched on
if fmt.tactic == DefinitiveListTactic::Vertical {
// if the tactic is Vertical, write_list already added a trailing ,
fields_str.push_str(" ");
} else {
fields_str.push_str(", ");
}
}
fields_str.push_str("..");
}
}
let fields_str = if context.config.struct_lit_style() == IndentStyle::Block &&
(fields_str.contains('\n') ||
context.config.struct_lit_multiline_style() ==
MultilineStyle::ForceMulti ||
fields_str.len() > h_shape.map(|s| s.width).unwrap_or(0)) {
format!("\n{}{}\n{}",
v_shape.indent.to_string(context.config),
fields_str,
shape.indent.to_string(context.config))
} else {
// One liner or visual indent.
format!(" {} ", fields_str)
};
Some(format!("{} {{{}}}", path_str, fields_str))
}
impl Rewrite for FieldPat {
fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
let pat = self.pat.rewrite(context, shape);
if self.is_shorthand {
pat
} else {
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wrap_str(format!("{}: {}", self.ident.to_string(), try_opt!(pat)),
context.config.max_width(),
shape)
}
}
}
enum TuplePatField<'a> {
Pat(&'a ptr::P<ast::Pat>),
Dotdot(Span),
}
impl<'a> Rewrite for TuplePatField<'a> {
fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
match *self {
TuplePatField::Pat(ref p) => p.rewrite(context, shape),
TuplePatField::Dotdot(_) => Some("..".to_string()),
}
}
}
impl<'a> Spanned for TuplePatField<'a> {
fn span(&self) -> Span {
match *self {
TuplePatField::Pat(ref p) => p.span(),
TuplePatField::Dotdot(span) => span,
}
}
}
fn rewrite_tuple_pat(pats: &[ptr::P<ast::Pat>],
dotdot_pos: Option<usize>,
path_str: Option<String>,
span: Span,
context: &RewriteContext,
shape: Shape)
-> Option<String> {
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let mut pat_vec: Vec<_> = pats.into_iter().map(|x| TuplePatField::Pat(x)).collect();
if let Some(pos) = dotdot_pos {
let prev = if pos == 0 {
span.lo
} else {
pats[pos - 1].span().hi
};
let next = if pos + 1 >= pats.len() {
span.hi
} else {
pats[pos + 1].span().lo
};
let dot_span = codemap::mk_sp(prev, next);
let snippet = context.snippet(dot_span);
let lo = dot_span.lo + BytePos(snippet.find_uncommented("..").unwrap() as u32);
let span = Span {
lo: lo,
// 2 == "..".len()
hi: lo + BytePos(2),
expn_id: codemap::NO_EXPANSION,
};
let dotdot = TuplePatField::Dotdot(span);
pat_vec.insert(pos, dotdot);
}
if pat_vec.is_empty() {
return Some(format!("{}()", try_opt!(path_str)));
}
// add comma if `(x,)`
let add_comma = path_str.is_none() && pat_vec.len() == 1 && dotdot_pos.is_none();
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let path_len = path_str.as_ref().map(|p| p.len()).unwrap_or(0);
// 2 = "()".len(), 3 = "(,)".len()
let nested_shape = try_opt!(shape.sub_width(path_len + if add_comma { 3 } else { 2 }));
// 1 = "(".len()
let nested_shape = nested_shape.visual_indent(path_len + 1);
let mut items: Vec<_> = itemize_list(context.codemap,
pat_vec.iter(),
if add_comma { ",)" } else { ")" },
|item| item.span().lo,
|item| item.span().hi,
|item| item.rewrite(context, nested_shape),
context.codemap.span_after(span, "("),
span.hi - BytePos(1))
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.collect();
// Condense wildcard string suffix into a single ..
let wildcard_suffix_len = count_wildcard_suffix_len(&items);
let list = if context.config.condense_wildcard_suffixes() && wildcard_suffix_len >= 2 {
let new_item_count = 1 + pats.len() - wildcard_suffix_len;
items[new_item_count - 1].item = Some("..".to_owned());
let da_iter = items.into_iter().take(new_item_count);
try_opt!(format_item_list(da_iter, nested_shape, context.config))
} else {
try_opt!(format_item_list(items.into_iter(), nested_shape, context.config))
};
match path_str {
Some(path_str) => {
Some(if context.config.spaces_within_parens() {
format!("{}( {} )", path_str, list)
} else {
format!("{}({})", path_str, list)
})
}
None => {
let comma = if add_comma { "," } else { "" };
Some(if context.config.spaces_within_parens() {
format!("( {}{} )", list, comma)
} else {
format!("({}{})", list, comma)
})
}
}
}
fn count_wildcard_suffix_len(items: &[ListItem]) -> usize {
let mut suffix_len = 0;
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for item in items.iter().rev().take_while(|i| match i.item {
Some(ref internal_string) if internal_string ==
"_" => true,
_ => false,
}) {
suffix_len += 1;
if item.pre_comment.is_some() || item.post_comment.is_some() {
break;
}
}
suffix_len
}