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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;
/// 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: &ast::Expr) -> bool {
match e.node {
ast::ExprIf(..) |
ast::ExprIfLet(..) |
ast::ExprMatch(..) |
ast::ExprBlock(_) |
ast::ExprWhile(..) |
ast::ExprWhileLet(..) |
ast::ExprLoop(..) |
ast::ExprForLoop(..) => false,
_ => true,
}
}
pub fn expr_is_simple_block(e: &ast::Expr) -> bool {
match e.node {
ast::ExprBlock(ref 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 {
match *stmt {
ast::StmtDecl(ref d, _) => {
match d.node {
ast::DeclLocal(_) => true,
ast::DeclItem(_) => false,
}
}
ast::StmtExpr(ref e, _) => expr_requires_semi_to_be_stmt(e),
ast::StmtSemi(..) => false,
ast::StmtMac(..) => false,
}
}
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