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auto merge of #17733 : jgallagher/rust/while-let, r=alexcrichton

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This is *heavily* based on `if let` (#17634) by @jakub- and @kballard

This should close #17687
This commit is contained in:
bors 2014-10-13 19:37:40 +00:00
commit c7e0724274
25 changed files with 266 additions and 15 deletions
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18
src/libsyntax/parse/parser.rs
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@ -26,7 +26,7 @@ use ast::{ExprField, ExprTupField, ExprFnBlock, ExprIf, ExprIfLet, ExprIndex, Ex
use ast::{ExprLit, ExprLoop, ExprMac};
use ast::{ExprMethodCall, ExprParen, ExprPath, ExprProc};
use ast::{ExprRepeat, ExprRet, ExprStruct, ExprTup, ExprUnary, ExprUnboxedFn};
use ast::{ExprVec, ExprWhile, ExprForLoop, Field, FnDecl};
use ast::{ExprVec, ExprWhile, ExprWhileLet, ExprForLoop, Field, FnDecl};
use ast::{Once, Many};
use ast::{FnUnboxedClosureKind, FnMutUnboxedClosureKind};
use ast::{FnOnceUnboxedClosureKind};
@ -2935,7 +2935,11 @@ impl<'a> Parser<'a> {
self.mk_expr(lo, hi, ExprForLoop(pat, expr, loop_block, opt_ident))
}
/// Parse a 'while' or 'while let' expression ('while' token already eaten)
pub fn parse_while_expr(&mut self, opt_ident: Option<ast::Ident>) -> P<Expr> {
if self.is_keyword(keywords::Let) {
return self.parse_while_let_expr(opt_ident);
}
let lo = self.last_span.lo;
let cond = self.parse_expr_res(RESTRICTION_NO_STRUCT_LITERAL);
let body = self.parse_block();
@ -2943,6 +2947,18 @@ impl<'a> Parser<'a> {
return self.mk_expr(lo, hi, ExprWhile(cond, body, opt_ident));
}
/// Parse a 'while let' expression ('while' token already eaten)
pub fn parse_while_let_expr(&mut self, opt_ident: Option<ast::Ident>) -> P<Expr> {
let lo = self.last_span.lo;
self.expect_keyword(keywords::Let);
let pat = self.parse_pat();
self.expect(&token::EQ);
let expr = self.parse_expr_res(RESTRICTION_NO_STRUCT_LITERAL);
let body = self.parse_block();
let hi = body.span.hi;
return self.mk_expr(lo, hi, ExprWhileLet(pat, expr, body, opt_ident));
}
pub fn parse_loop_expr(&mut self, opt_ident: Option<ast::Ident>) -> P<Expr> {
let lo = self.last_span.lo;
let body = self.parse_block();