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// Copyright 2012 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.
//! Routines the parser uses to classify AST nodes
// Predicates on exprs and stmts that the pretty-printer and parser use
use ast;
use std::gc::Gc;
// does this expression require a semicolon to be treated
// as a statement? The negation of this: 'can this expression
// be used as a statement without a semicolon' -- is used
// as an early-bail-out in the parser so that, for instance,
// 'if true {...} else {...}
// |x| 5 '
// isn't parsed as (if true {...} else {...} | x) | 5
pub fn expr_requires_semi_to_be_stmt(e: Gc<ast::Expr>) -> bool {
match e.node {
ast::ExprIf(..)
| ast::ExprMatch(..)
| ast::ExprBlock(_)
| ast::ExprWhile(..)
| ast::ExprLoop(..)
| ast::ExprForLoop(..) => false,
_ => true
}
}
pub fn expr_is_simple_block(e: Gc<ast::Expr>) -> bool {
match e.node {
ast::ExprBlock(block) => block.rules == ast::DefaultBlock,
_ => false
}
}
// this statement requires a semicolon after it.
// note that in one case (stmt_semi), we've already
// seen the semicolon, and thus don't need another.
pub fn stmt_ends_with_semi(stmt: &ast::Stmt) -> bool {
return match stmt.node {
ast::StmtDecl(d, _) => {
match d.node {
ast::DeclLocal(_) => true,
ast::DeclItem(_) => false
}
}
ast::StmtExpr(e, _) => { expr_requires_semi_to_be_stmt(e) }
ast::StmtSemi(..) => { false }
ast::StmtMac(..) => { false }
}
}
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