From 3daca3eb4d843199540edfb1092f57f49938d0f6 Mon Sep 17 00:00:00 2001
From: Marcus Klaas de Vries <mail@marcusklaas.nl>
Date: Mon, 28 Jan 2019 23:06:11 +0100
Subject: Infer type of match guard

---
 crates/ra_syntax/src/ast/generated.rs            |  6 +++++-
 crates/ra_syntax/src/grammar.ron                 |  2 +-
 crates/ra_syntax/src/grammar/expressions/atom.rs | 18 ++++++++++++++++--
 3 files changed, 22 insertions(+), 4 deletions(-)

(limited to 'crates/ra_syntax/src')

diff --git a/crates/ra_syntax/src/ast/generated.rs b/crates/ra_syntax/src/ast/generated.rs
index 3ace6533c..4f5a96014 100644
--- a/crates/ra_syntax/src/ast/generated.rs
+++ b/crates/ra_syntax/src/ast/generated.rs
@@ -1981,7 +1981,11 @@ impl ToOwned for MatchGuard {
 }
 
 
-impl MatchGuard {}
+impl MatchGuard {
+    pub fn expr(&self) -> Option<&Expr> {
+        super::child_opt(self)
+    }
+}
 
 // MethodCallExpr
 #[derive(Debug, PartialEq, Eq, Hash)]
diff --git a/crates/ra_syntax/src/grammar.ron b/crates/ra_syntax/src/grammar.ron
index 85fc79038..e4cad4eb3 100644
--- a/crates/ra_syntax/src/grammar.ron
+++ b/crates/ra_syntax/src/grammar.ron
@@ -418,7 +418,7 @@ Grammar(
             ],
             collections: [ [ "pats", "Pat" ] ]
         ),
-        "MatchGuard": (),
+        "MatchGuard": (options: ["Expr"]),
         "StructLit": (options: ["Path", "NamedFieldList", ["spread", "Expr"]]),
         "NamedFieldList": (collections: [ ["fields", "NamedField"] ]),
         "NamedField": (options: ["NameRef", "Expr"]),
diff --git a/crates/ra_syntax/src/grammar/expressions/atom.rs b/crates/ra_syntax/src/grammar/expressions/atom.rs
index 6d6d89f70..600774afd 100644
--- a/crates/ra_syntax/src/grammar/expressions/atom.rs
+++ b/crates/ra_syntax/src/grammar/expressions/atom.rs
@@ -360,8 +360,8 @@ fn match_arm(p: &mut Parser) -> BlockLike {
     while p.eat(PIPE) {
         patterns::pattern(p);
     }
-    if p.eat(IF_KW) {
-        expr(p);
+    if p.at(IF_KW) {
+        match_guard(p);
     }
     p.expect(FAT_ARROW);
     let ret = expr_stmt(p);
@@ -369,6 +369,20 @@ fn match_arm(p: &mut Parser) -> BlockLike {
     ret
 }
 
+// test match_guard
+// fn foo() {
+//     match () {
+//         _ if foo => (),
+//     }
+// }
+fn match_guard(p: &mut Parser) -> CompletedMarker {
+    assert!(p.at(IF_KW));
+    let m = p.start();
+    p.bump();
+    expr(p);
+    m.complete(p, MATCH_GUARD)
+}
+
 // test block_expr
 // fn foo() {
 //     {};
-- 
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