diff --git a/src/librustc/middle/check_match.rs b/src/librustc/middle/check_match.rs index 600d449ffe5..de9125ec449 100644 --- a/src/librustc/middle/check_match.rs +++ b/src/librustc/middle/check_match.rs @@ -267,8 +267,8 @@ fn check_arms(cx: &MatchCheckCtxt, arms: &[(Vec>, Option<&Expr>)], source // We don't want two, that's just confusing. } else { // find the first arm pattern so we can use its span - let &(ref first_arm_pats, _) = &arms[0]; // we know there's at least 1 arm - let first_pat = first_arm_pats.get(0); // and it's safe to assume 1 pat + let &(ref first_arm_pats, _) = &arms[0]; + let first_pat = first_arm_pats.get(0); let span = first_pat.span; span_err!(cx.tcx.sess, span, E0162, "irrefutable if-let pattern"); printed_if_let_err = true; diff --git a/src/libsyntax/ext/expand.rs b/src/libsyntax/ext/expand.rs index 76ca33cc2b8..fa3ccc8cf32 100644 --- a/src/libsyntax/ext/expand.rs +++ b/src/libsyntax/ext/expand.rs @@ -70,8 +70,6 @@ pub fn expand_expr(e: P, fld: &mut MacroExpander) -> P { // Desugar ExprIfLet // From: `if let = []` ast::ExprIfLet(pat, expr, body, mut elseopt) => { - let span = e.span; - // to: // // match { @@ -90,23 +88,33 @@ pub fn expand_expr(e: P, fld: &mut MacroExpander) -> P { let else_if_arms = { let mut arms = vec![]; loop { - // NOTE: replace with 'if let' after snapshot - match elseopt { - Some(els) => match els.node { - // else if - ast::ExprIf(cond, then, elseopt_) => { - let pat_under = fld.cx.pat_wild(span); - elseopt = elseopt_; - arms.push(ast::Arm { - attrs: vec![], - pats: vec![pat_under], - guard: Some(cond), - body: fld.cx.expr_block(then) - }); - } - _ => break - }, - None => break + let elseopt_continue = elseopt + .and_then(|els| els.and_then(|els| match els.node { + // else if + ast::ExprIf(cond, then, elseopt) => { + let pat_under = fld.cx.pat_wild(span); + arms.push(ast::Arm { + attrs: vec![], + pats: vec![pat_under], + guard: Some(cond), + body: fld.cx.expr_block(then) + }); + elseopt.map(|elseopt| (elseopt, true)) + } + _ => Some((P(els), false)) + })); + match elseopt_continue { + Some((e, true)) => { + elseopt = Some(e); + } + Some((e, false)) => { + elseopt = Some(e); + break; + } + None => { + elseopt = None; + break; + } } } arms @@ -115,10 +123,7 @@ pub fn expand_expr(e: P, fld: &mut MacroExpander) -> P { // `_ => [ | ()]` let else_arm = { let pat_under = fld.cx.pat_wild(span); - let else_expr = match elseopt { - Some(els) => els, - None => fld.cx.expr_lit(span, ast::LitNil) - }; + let else_expr = elseopt.unwrap_or_else(|| fld.cx.expr_lit(span, ast::LitNil)); fld.cx.arm(span, vec![pat_under], else_expr) }; @@ -133,23 +138,24 @@ pub fn expand_expr(e: P, fld: &mut MacroExpander) -> P { // Desugar support for ExprIfLet in the ExprIf else position ast::ExprIf(cond, blk, elseopt) => { - let elseopt = elseopt.map(|els| match els.node { + let elseopt = elseopt.map(|els| els.and_then(|els| match els.node { ast::ExprIfLet(..) => { // wrap the if-let expr in a block + let span = els.span; let blk = P(ast::Block { view_items: vec![], stmts: vec![], - expr: Some(els), + expr: Some(P(els)), id: ast::DUMMY_NODE_ID, rules: ast::DefaultBlock, - span: els.span + span: span }); fld.cx.expr_block(blk) } - _ => els - }); - let if_expr = fld.cx.expr(e.span, ast::ExprIf(cond, blk, elseopt)); - noop_fold_expr(if_expr, fld) + _ => P(els) + })); + let if_expr = fld.cx.expr(span, ast::ExprIf(cond, blk, elseopt)); + if_expr.map(|e| noop_fold_expr(e, fld)) } ast::ExprLoop(loop_block, opt_ident) => {