From 5205c016e9f704796aa7893f89ef108248bda2e2 Mon Sep 17 00:00:00 2001
From: DJMcNab <36049421+DJMcNab@users.noreply.github.com>
Date: Thu, 20 Dec 2018 11:35:02 +0000
Subject: Fix ambiguity with if break

Brought up by #290
---
 crates/ra_syntax/src/grammar/expressions.rs      |  5 +++++
 crates/ra_syntax/src/grammar/expressions/atom.rs | 21 ++++++++++++++++-----
 2 files changed, 21 insertions(+), 5 deletions(-)

(limited to 'crates/ra_syntax/src')

diff --git a/crates/ra_syntax/src/grammar/expressions.rs b/crates/ra_syntax/src/grammar/expressions.rs
index 4f8c46ab3..79de0add0 100644
--- a/crates/ra_syntax/src/grammar/expressions.rs
+++ b/crates/ra_syntax/src/grammar/expressions.rs
@@ -5,6 +5,7 @@ pub(super) use self::atom::{literal, LITERAL_FIRST};
 use super::*;
 
 const EXPR_FIRST: TokenSet = LHS_FIRST;
+const EXPR_FIRST_NO_BLOCK: TokenSet = LHS_FIRST_NO_BLOCK;
 
 pub(super) fn expr(p: &mut Parser) -> BlockLike {
     let r = Restrictions {
@@ -209,6 +210,10 @@ const LHS_FIRST: TokenSet = token_set_union![
     token_set![AMP, STAR, EXCL, DOTDOT, MINUS],
     atom::ATOM_EXPR_FIRST,
 ];
+const LHS_FIRST_NO_BLOCK: TokenSet = token_set_union![
+    token_set![AMP, STAR, EXCL, DOTDOT, MINUS],
+    atom::ATOM_EXPR_FIRST_NO_BLOCK,
+];
 
 fn lhs(p: &mut Parser, r: Restrictions) -> Option<(CompletedMarker, BlockLike)> {
     let m;
diff --git a/crates/ra_syntax/src/grammar/expressions/atom.rs b/crates/ra_syntax/src/grammar/expressions/atom.rs
index cd7d62aff..fcc0a4490 100644
--- a/crates/ra_syntax/src/grammar/expressions/atom.rs
+++ b/crates/ra_syntax/src/grammar/expressions/atom.rs
@@ -35,10 +35,10 @@ pub(crate) fn literal(p: &mut Parser) -> Option<CompletedMarker> {
     Some(m.complete(p, LITERAL))
 }
 
-pub(super) const ATOM_EXPR_FIRST: TokenSet = token_set_union![
+// E.g. for after the break in `if break {}`, this should not match
+pub(super) const ATOM_EXPR_FIRST_NO_BLOCK: TokenSet = token_set_union![
     LITERAL_FIRST,
     token_set![
-        L_CURLY,
         L_PAREN,
         L_BRACK,
         PIPE,
@@ -59,6 +59,9 @@ pub(super) const ATOM_EXPR_FIRST: TokenSet = token_set_union![
     ],
 ];
 
+pub(super) const ATOM_EXPR_FIRST: TokenSet =
+    token_set_union![ATOM_EXPR_FIRST_NO_BLOCK, token_set![L_CURLY],];
+
 const EXPR_RECOVERY_SET: TokenSet = token_set![LET_KW];
 
 pub(super) fn atom_expr(p: &mut Parser, r: Restrictions) -> Option<(CompletedMarker, BlockLike)> {
@@ -108,7 +111,7 @@ pub(super) fn atom_expr(p: &mut Parser, r: Restrictions) -> Option<(CompletedMar
         L_CURLY => block_expr(p, None),
         RETURN_KW => return_expr(p),
         CONTINUE_KW => continue_expr(p),
-        BREAK_KW => break_expr(p),
+        BREAK_KW => break_expr(p, r),
         _ => {
             p.err_recover("expected expression", EXPR_RECOVERY_SET);
             return None;
@@ -427,12 +430,20 @@ fn continue_expr(p: &mut Parser) -> CompletedMarker {
 //         break 'l 92;
 //     }
 // }
-fn break_expr(p: &mut Parser) -> CompletedMarker {
+fn break_expr(p: &mut Parser, r: Restrictions) -> CompletedMarker {
     assert!(p.at(BREAK_KW));
     let m = p.start();
     p.bump();
     p.eat(LIFETIME);
-    if p.at_ts(EXPR_FIRST) {
+    // test break_ambiguity
+    // fn foo(){
+    //     if break {}
+    //     while break {}
+    //     for i in break {}
+    //     match break {}
+    // }
+    if r.forbid_structs && p.at_ts(EXPR_FIRST_NO_BLOCK) || !r.forbid_structs && p.at_ts(EXPR_FIRST)
+    {
         expr(p);
     }
     m.complete(p, BREAK_EXPR)
-- 
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