Accept parenthesized type args for error recovery

Author: estebank

src/librustc/hir/lowering.rs

@@ -1826,7 +1826,11 @@ impl<'a> LoweringContext<'a> {
                         struct_span_err!(self.sess, data.span, E0214, "{}", msg)
                             .span_label(data.span, "only traits may use parentheses")
                             .emit();
-                        (hir::GenericArgs::none(), false)
+                        (self.lower_angle_bracketed_parameter_data(
+                            &data.as_angle_bracketed_args(),
+                            param_mode,
+                            itctx).0,
+                         false)
                     }
                 },
             }

src/libsyntax/ast.rs

@@ -192,6 +192,16 @@ pub struct ParenthesisedArgs {
     pub output: Option<P<Ty>>,
 }
 
+impl ParenthesisedArgs {
+    pub fn as_angle_bracketed_args(&self) -> AngleBracketedArgs {
+        AngleBracketedArgs {
+            span: self.span,
+            args: self.inputs.iter().cloned().map(|input| GenericArg::Type(input)).collect(),
+            bindings: vec![],
+        }
+    }
+}
+
 // hack to ensure that we don't try to access the private parts of `NodeId` in this module
 mod node_id_inner {
     use rustc_data_structures::indexed_vec::Idx;

src/test/ui/error-codes/E0214.stderr

@@ -4,13 +4,6 @@ error[E0214]: parenthesized parameters may only be used with a trait
 LL |     let v: Vec(&str) = vec!["foo"];
    |               ^^^^^^ only traits may use parentheses
 
-error[E0107]: wrong number of type arguments: expected 1, found 0
-  --> $DIR/E0214.rs:2:12
-   |
-LL |     let v: Vec(&str) = vec!["foo"];
-   |            ^^^^^^^^^ expected 1 type argument
-
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
-Some errors occurred: E0107, E0214.
-For more information about an error, try `rustc --explain E0107`.
+For more information about this error, try `rustc --explain E0214`.

src/test/ui/issues/issue-23589.rs

@@ -1,4 +1,5 @@
 fn main() {
     let v: Vec(&str) = vec!['1', '2'];
     //~^ ERROR parenthesized parameters may only be used with a trait
+    //~| ERROR mismatched types
 }

src/test/ui/issues/issue-23589.stderr

@@ -4,13 +4,16 @@ error[E0214]: parenthesized parameters may only be used with a trait
 LL |     let v: Vec(&str) = vec!['1', '2'];
    |               ^^^^^^ only traits may use parentheses
 
-error[E0107]: wrong number of type arguments: expected 1, found 0
-  --> $DIR/issue-23589.rs:2:12
+error[E0308]: mismatched types
+  --> $DIR/issue-23589.rs:2:29
    |
 LL |     let v: Vec(&str) = vec!['1', '2'];
-   |            ^^^^^^^^^ expected 1 type argument
+   |                             ^^^ expected &str, found char
+   |
+   = note: expected type `&str`
+              found type `char`
 
 error: aborting due to 2 previous errors
 
-Some errors occurred: E0107, E0214.
-For more information about an error, try `rustc --explain E0107`.
+Some errors occurred: E0214, E0308.
+For more information about an error, try `rustc --explain E0214`.

src/test/ui/unboxed-closures/unboxed-closure-sugar-used-on-struct-1.rs

@@ -7,6 +7,7 @@ struct Bar<A> {
 fn bar() {
     let x: Box<Bar()> = panic!();
     //~^ ERROR parenthesized parameters may only be used with a trait
+    //~| ERROR wrong number of type arguments: expected 1, found 0
 }
 
 fn main() { }

src/test/ui/unboxed-closures/unboxed-closure-sugar-used-on-struct-3.stderr

@@ -4,13 +4,6 @@ error[E0214]: parenthesized parameters may only be used with a trait
 LL |     let b = Bar::(isize, usize)::new(); // OK too (for the parser)
    |                ^^^^^^^^^^^^^^^^ only traits may use parentheses
 
-error[E0107]: wrong number of type arguments: expected 2, found 0
-  --> $DIR/unboxed-closure-sugar-used-on-struct-3.rs:14:13
-   |
-LL |     let b = Bar::(isize, usize)::new(); // OK too (for the parser)
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^ expected 2 type arguments
-
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
-Some errors occurred: E0107, E0214.
-For more information about an error, try `rustc --explain E0107`.
+For more information about this error, try `rustc --explain E0214`.

src/test/ui/unboxed-closures/unboxed-closure-sugar-used-on-struct.rs

@@ -6,7 +6,7 @@ struct Bar<A> {
 
 fn foo(b: Box<Bar()>) {
     //~^ ERROR parenthesized parameters may only be used with a trait
-    //~| ERROR the type placeholder `_` is not allowed within types on item signatures
+    //~| ERROR wrong number of type arguments: expected 1, found 0
 }
 
 fn main() { }