From 049f0a6d2c31e8f5f4787cb7e3e89834cbb50ac4 Mon Sep 17 00:00:00 2001
From: hkalbasi <hamidrezakalbasi@protonmail.com>
Date: Fri, 1 Apr 2022 17:20:54 +0430
Subject: [PATCH] recover from missing type annotation

---
 crates/hir_ty/src/tests/simple.rs  | 14 ++++++++++++++
 crates/parser/src/grammar/types.rs |  6 ++++++
 2 files changed, 20 insertions(+)

diff --git a/crates/hir_ty/src/tests/simple.rs b/crates/hir_ty/src/tests/simple.rs
index df7b3df3d5..baed34ce23 100644
--- a/crates/hir_ty/src/tests/simple.rs
+++ b/crates/hir_ty/src/tests/simple.rs
@@ -2556,6 +2556,20 @@ fn f() {
     )
 }
 
+#[test]
+fn infer_missing_type() {
+    check_types(
+        r#"
+struct S;
+
+fn f() {
+    let s: = S;
+      //^ S
+}
+    "#,
+    );
+}
+
 #[test]
 fn infer_type_alias_variant() {
     check_infer(
diff --git a/crates/parser/src/grammar/types.rs b/crates/parser/src/grammar/types.rs
index ff067f5293..46db487d02 100644
--- a/crates/parser/src/grammar/types.rs
+++ b/crates/parser/src/grammar/types.rs
@@ -57,6 +57,12 @@ fn type_with_bounds_cond(p: &mut Parser, allow_bounds: bool) {
 pub(super) fn ascription(p: &mut Parser) {
     assert!(p.at(T![:]));
     p.bump(T![:]);
+    if p.at(T![=]) {
+        // recover from `let x: = expr;`, `const X: = expr;` and similars
+        // hopefully no type starts with `=`
+        p.error("missing type");
+        return;
+    }
     type_(p);
 }