1 // Copyright 2012 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
4 //
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
10
11 //! Routines the parser uses to classify AST nodes
12
13 // Predicates on exprs and stmts that the pretty-printer and parser use
14
15 use ast;
16
17 // does this expression require a semicolon to be treated
18 // as a statement? The negation of this: 'can this expression
19 // be used as a statement without a semicolon' -- is used
20 // as an early-bail-out in the parser so that, for instance,
21 // 'if true {...} else {...}
22 // |x| 5 '
23 // isn't parsed as (if true {...} else {...} | x) | 5
24 pub fn expr_requires_semi_to_be_stmt(e: @ast::Expr) -> bool {
25 match e.node {
26 ast::ExprIf(..)
27 | ast::ExprMatch(..)
28 | ast::ExprBlock(_)
29 | ast::ExprWhile(..)
30 | ast::ExprLoop(..)
31 | ast::ExprForLoop(..) => false,
32 _ => true
33 }
34 }
35
36 pub fn expr_is_simple_block(e: @ast::Expr) -> bool {
37 match e.node {
38 ast::ExprBlock(block) => block.rules == ast::DefaultBlock,
39 _ => false
40 }
41 }
42
43 // this statement requires a semicolon after it.
44 // note that in one case (stmt_semi), we've already
45 // seen the semicolon, and thus don't need another.
46 pub fn stmt_ends_with_semi(stmt: &ast::Stmt) -> bool {
47 return match stmt.node {
48 ast::StmtDecl(d, _) => {
49 match d.node {
50 ast::DeclLocal(_) => true,
51 ast::DeclItem(_) => false
52 }
53 }
54 ast::StmtExpr(e, _) => { expr_requires_semi_to_be_stmt(e) }
55 ast::StmtSemi(..) => { false }
56 ast::StmtMac(..) => { false }
57 }
58 }