const type with colon also get type infer

Author: chenyukang

compiler/rustc_parse/src/parser/item.rs

@@ -1176,14 +1176,13 @@ impl<'a> Parser<'a> {
         m: Option<Mutability>,
     ) -> PResult<'a, (Ident, P<Ty>, Option<P<ast::Expr>>)> {
         let id = if m.is_none() { self.parse_ident_or_underscore() } else { self.parse_ident() }?;
-
         // Parse the type of a `const` or `static mut?` item.
         // That is, the `":" $ty` fragment.
-        let ty = if self.eat(&token::Colon) {
-            self.parse_ty()?
-        } else {
+        let _ = self.eat(&token::Colon);
+        let ty = self.parse_ty().unwrap_or_else(|e| {
+            e.cancel();
             self.recover_missing_const_type(id, m)
-        };
+        });
 
         let expr = if self.eat(&token::Eq) { Some(self.parse_expr()?) } else { None };
         self.expect_semi()?;

src/test/ui/parser/removed-syntax-static-fn.rs

@@ -3,8 +3,7 @@ struct S;
 impl S {
     static fn f() {}
     //~^ ERROR expected identifier, found keyword `fn`
-    //~| ERROR expected one of `:`, `;`, or `=`
-    //~| ERROR missing type for `static` item
+    //~| ERROR expected one of `!`, `+`, `->`, `::`, `;`, or `=`, found `{`
 }
 
 fn main() {}

src/test/ui/parser/removed-syntax-static-fn.stderr

@@ -4,22 +4,16 @@ error: expected identifier, found keyword `fn`
 LL |     static fn f() {}
    |            ^^ expected identifier, found keyword
 
-error: expected one of `:`, `;`, or `=`, found `f`
-  --> $DIR/removed-syntax-static-fn.rs:4:15
+error: expected one of `!`, `+`, `->`, `::`, `;`, or `=`, found `{`
+  --> $DIR/removed-syntax-static-fn.rs:4:19
    |
 LL | impl S {
    |        - while parsing this item list starting here
 LL |     static fn f() {}
-   |               ^ expected one of `:`, `;`, or `=`
+   |                   ^ expected one of `!`, `+`, `->`, `::`, `;`, or `=`
 ...
 LL | }
    | - the item list ends here
 
-error: missing type for `static` item
-  --> $DIR/removed-syntax-static-fn.rs:4:12
-   |
-LL |     static fn f() {}
-   |            ^^ help: provide a type for the item: `r#fn: <type>`
-
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors
 

src/test/ui/suggestions/const-without-type-but-colon.rs

@@ -0,0 +1,9 @@
+fn main() {
+    const a: = 123;
+    //~^ ERROR missing type for `const` item
+    const b = 345;
+    //~^ ERROR missing type for `const` item
+
+    const c: = "hello";
+    //~^ ERROR missing type for `const` item
+}

src/test/ui/suggestions/const-without-type-but-colon.stderr

@@ -0,0 +1,20 @@
+error: missing type for `const` item
+  --> $DIR/const-without-type-but-colon.rs:2:11
+   |
+LL |     const a: = 123;
+   |           ^ help: provide a type for the constant: `a: i32`
+
+error: missing type for `const` item
+  --> $DIR/const-without-type-but-colon.rs:4:11
+   |
+LL |     const b = 345;
+   |           ^ help: provide a type for the constant: `b: i32`
+
+error: missing type for `const` item
+  --> $DIR/const-without-type-but-colon.rs:7:11
+   |
+LL |     const c: = "hello";
+   |           ^ help: provide a type for the constant: `c: &str`
+
+error: aborting due to 3 previous errors
+