Auto merge of #35130 - sanxiyn:unused-type-parameter-error, r=nrc

Suppress unused type parameter error when type has error field

Fix #35075.

Author: bors

src/librustc/ty/util.rs

@@ -182,6 +182,21 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         pat_util::arm_contains_ref_binding(arm)
     }
 
+    pub fn has_error_field(self, ty: Ty<'tcx>) -> bool {
+        match ty.sty {
+            ty::TyStruct(def, substs) | ty::TyEnum(def, substs) => {
+                for field in def.all_fields() {
+                    let field_ty = field.ty(self, substs);
+                    if let TyError = field_ty.sty {
+                        return true;
+                    }
+                }
+            }
+            _ => ()
+        }
+        false
+    }
+
     /// Returns the type of element at index `i` in tuple or tuple-like type `t`.
     /// For an enum `t`, `variant` is None only if `t` is a univariant enum.
     pub fn positional_element_ty(self,

src/librustc_typeck/check/wfcheck.rs

@@ -454,6 +454,11 @@ impl<'ccx, 'gcx> CheckTypeWellFormedVisitor<'ccx, 'gcx> {
                                      item: &hir::Item,
                                      ast_generics: &hir::Generics)
     {
+        let ty = self.tcx().node_id_to_type(item.id);
+        if self.tcx().has_error_field(ty) {
+            return;
+        }
+
         let item_def_id = self.tcx().map.local_def_id(item.id);
         let ty_predicates = self.tcx().lookup_predicates(item_def_id);
         let variances = self.tcx().item_variances(item_def_id);

src/test/compile-fail/issue-35075.rs

@@ -0,0 +1,19 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+struct Bar<T> {
+    inner: Foo<T> //~ ERROR type name `Foo` is undefined or not in scope
+}
+
+enum Baz<T> {
+    Foo(Foo<T>) //~ ERROR type name `Foo` is undefined or not in scope
+}
+
+fn main() {}

src/test/compile-fail/resolve-type-param-in-item-in-trait.rs

@@ -13,33 +13,30 @@
 // scope (in this case, the enum).
 
 trait TraitA<A> {
-    fn outer(self) {
+    fn outer(&self) {
         enum Foo<B> {
-            //~^ ERROR parameter `B` is never used
             Variance(A)
                 //~^ ERROR can't use type parameters from outer function
         }
     }
 }
 
 trait TraitB<A> {
-    fn outer(self) {
+    fn outer(&self) {
         struct Foo<B>(A);
                 //~^ ERROR can't use type parameters from outer function
-                //~^^ ERROR parameter `B` is never used
     }
 }
 
 trait TraitC<A> {
-    fn outer(self) {
+    fn outer(&self) {
         struct Foo<B> { a: A }
                 //~^ ERROR can't use type parameters from outer function
-                //~^^ ERROR parameter `B` is never used
     }
 }
 
 trait TraitD<A> {
-    fn outer(self) {
+    fn outer(&self) {
         fn foo<B>(a: A) { }
                 //~^ ERROR can't use type parameters from outer function
     }