rust/src/macros.rs
Nick Cameron 9eb78a3333 Fallout
2017-02-23 13:15:48 +13:00

208 lines
7.0 KiB
Rust

// 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.
// Format list-like macro invocations. These are invocations whose token trees
// can be interpreted as expressions and separated by commas.
// Note that these token trees do not actually have to be interpreted as
// expressions by the compiler. An example of an invocation we would reformat is
// foo!( x, y, z ). The token x may represent an identifier in the code, but we
// interpreted as an expression.
// Macro uses which are not-list like, such as bar!(key => val), will not be
// reformated.
// List-like invocations with parentheses will be formatted as function calls,
// and those with brackets will be formatted as array literals.
use syntax::ast;
use syntax::codemap::{mk_sp, BytePos};
use syntax::parse::token::Token;
use syntax::parse::tts_to_parser;
use syntax::symbol;
use syntax::util::ThinVec;
use Shape;
use codemap::SpanUtils;
use rewrite::{Rewrite, RewriteContext};
use expr::{rewrite_call, rewrite_array};
use comment::{FindUncommented, contains_comment};
const FORCED_BRACKET_MACROS: &'static [&'static str] = &["vec!"];
// FIXME: use the enum from libsyntax?
#[derive(Clone, Copy, PartialEq, Eq)]
enum MacroStyle {
Parens,
Brackets,
Braces,
}
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum MacroPosition {
Item,
Statement,
Expression,
}
impl MacroStyle {
fn opener(&self) -> &'static str {
match *self {
MacroStyle::Parens => "(",
MacroStyle::Brackets => "[",
MacroStyle::Braces => "{",
}
}
}
pub fn rewrite_macro(mac: &ast::Mac,
extra_ident: Option<ast::Ident>,
context: &RewriteContext,
shape: Shape,
position: MacroPosition)
-> Option<String> {
if context.config.use_try_shorthand {
if let Some(expr) = convert_try_mac(mac, context) {
return expr.rewrite(context, shape);
}
}
let original_style = macro_style(mac, context);
let macro_name = match extra_ident {
None => format!("{}!", mac.node.path),
Some(ident) => {
if ident == symbol::keywords::Invalid.ident() {
format!("{}!", mac.node.path)
} else {
format!("{}! {}", mac.node.path, ident)
}
}
};
let style = if FORCED_BRACKET_MACROS.contains(&&macro_name[..]) {
MacroStyle::Brackets
} else {
original_style
};
if mac.node.tts.is_empty() && !contains_comment(&context.snippet(mac.span)) {
return match style {
MacroStyle::Parens if position == MacroPosition::Item => {
Some(format!("{}();", macro_name))
}
MacroStyle::Parens => Some(format!("{}()", macro_name)),
MacroStyle::Brackets => Some(format!("{}[]", macro_name)),
MacroStyle::Braces => Some(format!("{}{{}}", macro_name)),
};
}
let mut parser = tts_to_parser(context.parse_session, mac.node.tts.clone());
let mut expr_vec = Vec::new();
if MacroStyle::Braces != style {
loop {
let expr = match parser.parse_expr() {
Ok(expr) => {
// Recovered errors.
if context.parse_session.span_diagnostic.has_errors() {
return None;
}
expr
}
Err(mut e) => {
e.cancel();
return None;
}
};
expr_vec.push(expr);
match parser.token {
Token::Eof => break,
Token::Comma => (),
_ => return None,
}
parser.bump();
if parser.token == Token::Eof {
// vec! is a special case of bracket macro which should be formated as an array.
if macro_name == "vec!" {
break;
} else {
return None;
}
}
}
}
match style {
MacroStyle::Parens => {
// Format macro invocation as function call.
rewrite_call(context, &macro_name, &expr_vec, mac.span, shape).map(|rw| {
match position {
MacroPosition::Item => format!("{};", rw),
_ => rw,
}
})
}
MacroStyle::Brackets => {
// Format macro invocation as array literal.
let extra_offset = macro_name.len();
let shape = try_opt!(shape.shrink_left(extra_offset));
let rewrite = try_opt!(rewrite_array(expr_vec.iter().map(|x| &**x),
mk_sp(context.codemap
.span_after(mac.span,
original_style.opener()),
mac.span.hi - BytePos(1)),
context,
shape));
Some(format!("{}{}", macro_name, rewrite))
}
MacroStyle::Braces => {
// Skip macro invocations with braces, for now.
None
}
}
}
/// Tries to convert a macro use into a short hand try expression. Returns None
/// when the macro is not an instance of try! (or parsing the inner expression
/// failed).
pub fn convert_try_mac(mac: &ast::Mac, context: &RewriteContext) -> Option<ast::Expr> {
if &format!("{}", mac.node.path)[..] == "try" {
let mut parser = tts_to_parser(context.parse_session, mac.node.tts.clone());
Some(ast::Expr {
id: ast::NodeId::new(0), // dummy value
node: ast::ExprKind::Try(try_opt!(parser.parse_expr().ok())),
span: mac.span, // incorrect span, but shouldn't matter too much
attrs: ThinVec::new(),
})
} else {
None
}
}
fn macro_style(mac: &ast::Mac, context: &RewriteContext) -> MacroStyle {
let snippet = context.snippet(mac.span);
let paren_pos = snippet.find_uncommented("(").unwrap_or(usize::max_value());
let bracket_pos = snippet.find_uncommented("[").unwrap_or(usize::max_value());
let brace_pos = snippet.find_uncommented("{").unwrap_or(usize::max_value());
if paren_pos < bracket_pos && paren_pos < brace_pos {
MacroStyle::Parens
} else if bracket_pos < brace_pos {
MacroStyle::Brackets
} else {
MacroStyle::Braces
}
}