diff --git a/src/librustc_typeck/astconv.rs b/src/librustc_typeck/astconv.rs
index 710f02cdedba3..8daefb618d35f 100644
--- a/src/librustc_typeck/astconv.rs
+++ b/src/librustc_typeck/astconv.rs
@@ -514,7 +514,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         self_ty: Option<Ty<'tcx>>,
         arg_count_correct: bool,
         args_for_def_id: impl Fn(DefId) -> (Option<&'b GenericArgs<'b>>, bool),
-        provided_kind: impl Fn(&GenericParamDef, &GenericArg<'_>) -> subst::GenericArg<'tcx>,
+        mut provided_kind: impl FnMut(&GenericParamDef, &GenericArg<'_>) -> subst::GenericArg<'tcx>,
         mut inferred_kind: impl FnMut(
             Option<&[subst::GenericArg<'tcx>]>,
             &GenericParamDef,
@@ -751,6 +751,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         };
 
         let mut missing_type_params = vec![];
+        let mut inferred_params = vec![];
         let substs = Self::create_substs_for_generic_args(
             tcx,
             def_id,
@@ -773,7 +774,12 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                     self.ast_region_to_region(&lt, Some(param)).into()
                 }
                 (GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => {
-                    self.ast_ty_to_ty(&ty).into()
+                    if let (hir::TyKind::Infer, false) = (&ty.kind, self.allow_ty_infer()) {
+                        inferred_params.push(ty.span);
+                        tcx.types.err.into()
+                    } else {
+                        self.ast_ty_to_ty(&ty).into()
+                    }
                 }
                 (GenericParamDefKind::Const, GenericArg::Const(ct)) => {
                     self.ast_const_to_const(&ct.value, tcx.type_of(param.def_id)).into()
@@ -832,6 +838,18 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 }
             },
         );
+        if !inferred_params.is_empty() {
+            // We always collect the spans for placeholder types when evaluating `fn`s, but we
+            // only want to emit an error complaining about them if infer types (`_`) are not
+            // allowed. `allow_ty_infer` gates this behavior.
+            crate::collect::placeholder_type_error(
+                tcx,
+                inferred_params[0],
+                &[],
+                inferred_params,
+                false,
+            );
+        }
 
         self.complain_about_missing_type_params(
             missing_type_params,
diff --git a/src/librustc_typeck/collect.rs b/src/librustc_typeck/collect.rs
index 1fade1b5ca65e..f257fc5442cc1 100644
--- a/src/librustc_typeck/collect.rs
+++ b/src/librustc_typeck/collect.rs
@@ -320,7 +320,7 @@ impl AstConv<'tcx> for ItemCtxt<'tcx> {
     }
 
     fn ty_infer(&self, _: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
-        placeholder_type_error(self.tcx(), span, &[], vec![span], false);
+        self.tcx().sess.delay_span_bug(span, "bad placeholder type");
         self.tcx().types.err
     }
 
@@ -715,13 +715,21 @@ fn convert_trait_item(tcx: TyCtxt<'_>, trait_item_id: hir::HirId) {
     tcx.generics_of(def_id);
 
     match trait_item.kind {
-        hir::TraitItemKind::Const(..)
-        | hir::TraitItemKind::Type(_, Some(_))
-        | hir::TraitItemKind::Method(..) => {
+        hir::TraitItemKind::Method(..) => {
             tcx.type_of(def_id);
-            if let hir::TraitItemKind::Method(..) = trait_item.kind {
-                tcx.fn_sig(def_id);
-            }
+            tcx.fn_sig(def_id);
+        }
+
+        hir::TraitItemKind::Const(.., Some(_)) => {
+            tcx.type_of(def_id);
+        }
+
+        hir::TraitItemKind::Const(..) | hir::TraitItemKind::Type(_, Some(_)) => {
+            tcx.type_of(def_id);
+            // Account for `const C: _;` and `type T = _;`.
+            let mut visitor = PlaceholderHirTyCollector::default();
+            visitor.visit_trait_item(trait_item);
+            placeholder_type_error(tcx, DUMMY_SP, &[], visitor.0, false);
         }
 
         hir::TraitItemKind::Type(_, None) => {}
@@ -735,8 +743,18 @@ fn convert_impl_item(tcx: TyCtxt<'_>, impl_item_id: hir::HirId) {
     tcx.generics_of(def_id);
     tcx.type_of(def_id);
     tcx.predicates_of(def_id);
-    if let hir::ImplItemKind::Method(..) = tcx.hir().expect_impl_item(impl_item_id).kind {
-        tcx.fn_sig(def_id);
+    let impl_item = tcx.hir().expect_impl_item(impl_item_id);
+    match impl_item.kind {
+        hir::ImplItemKind::Method(..) => {
+            tcx.fn_sig(def_id);
+        }
+        hir::ImplItemKind::TyAlias(_) | hir::ImplItemKind::OpaqueTy(_) => {
+            // Account for `type T = _;`
+            let mut visitor = PlaceholderHirTyCollector::default();
+            visitor.visit_impl_item(impl_item);
+            placeholder_type_error(tcx, DUMMY_SP, &[], visitor.0, false);
+        }
+        hir::ImplItemKind::Const(..) => {}
     }
 }
 
diff --git a/src/test/ui/did_you_mean/bad-assoc-ty.rs b/src/test/ui/did_you_mean/bad-assoc-ty.rs
index f02931eeb6fc3..00845a17b116b 100644
--- a/src/test/ui/did_you_mean/bad-assoc-ty.rs
+++ b/src/test/ui/did_you_mean/bad-assoc-ty.rs
@@ -17,7 +17,6 @@ type D = (u8, u8)::AssocTy;
 type E = _::AssocTy;
 //~^ ERROR missing angle brackets in associated item path
 //~| ERROR the type placeholder `_` is not allowed within types on item signatures
-//~| ERROR the type placeholder `_` is not allowed within types on item signatures
 
 type F = &'static (u8)::AssocTy;
 //~^ ERROR missing angle brackets in associated item path
@@ -46,4 +45,8 @@ type I = ty!()::AssocTy;
 //~^ ERROR missing angle brackets in associated item path
 //~| ERROR ambiguous associated type
 
+trait K<A, B> {}
+fn foo<X: K<_, _>>(x: X) {}
+//~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+
 fn main() {}
diff --git a/src/test/ui/did_you_mean/bad-assoc-ty.stderr b/src/test/ui/did_you_mean/bad-assoc-ty.stderr
index d5b2abf2f8b50..6d5f3d9f14348 100644
--- a/src/test/ui/did_you_mean/bad-assoc-ty.stderr
+++ b/src/test/ui/did_you_mean/bad-assoc-ty.stderr
@@ -29,25 +29,25 @@ LL | type E = _::AssocTy;
    |          ^^^^^^^^^^ help: try: `<_>::AssocTy`
 
 error: missing angle brackets in associated item path
-  --> $DIR/bad-assoc-ty.rs:22:19
+  --> $DIR/bad-assoc-ty.rs:21:19
    |
 LL | type F = &'static (u8)::AssocTy;
    |                   ^^^^^^^^^^^^^ help: try: `<(u8)>::AssocTy`
 
 error: missing angle brackets in associated item path
-  --> $DIR/bad-assoc-ty.rs:28:10
+  --> $DIR/bad-assoc-ty.rs:27:10
    |
 LL | type G = dyn 'static + (Send)::AssocTy;
    |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `<dyn 'static + (Send)>::AssocTy`
 
 error: missing angle brackets in associated item path
-  --> $DIR/bad-assoc-ty.rs:45:10
+  --> $DIR/bad-assoc-ty.rs:44:10
    |
 LL | type I = ty!()::AssocTy;
    |          ^^^^^^^^^^^^^^ help: try: `<ty!()>::AssocTy`
 
 error: missing angle brackets in associated item path
-  --> $DIR/bad-assoc-ty.rs:38:19
+  --> $DIR/bad-assoc-ty.rs:37:19
    |
 LL |     ($ty: ty) => ($ty::AssocTy);
    |                   ^^^^^^^^^^^^ help: try: `<$ty>::AssocTy`
@@ -87,32 +87,26 @@ error[E0121]: the type placeholder `_` is not allowed within types on item signa
 LL | type E = _::AssocTy;
    |          ^ not allowed in type signatures
 
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/bad-assoc-ty.rs:17:10
-   |
-LL | type E = _::AssocTy;
-   |          ^ not allowed in type signatures
-
 error[E0223]: ambiguous associated type
-  --> $DIR/bad-assoc-ty.rs:22:19
+  --> $DIR/bad-assoc-ty.rs:21:19
    |
 LL | type F = &'static (u8)::AssocTy;
    |                   ^^^^^^^^^^^^^ help: use fully-qualified syntax: `<u8 as Trait>::AssocTy`
 
 error[E0223]: ambiguous associated type
-  --> $DIR/bad-assoc-ty.rs:28:10
+  --> $DIR/bad-assoc-ty.rs:27:10
    |
 LL | type G = dyn 'static + (Send)::AssocTy;
    |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use fully-qualified syntax: `<(dyn std::marker::Send + 'static) as Trait>::AssocTy`
 
 error[E0223]: ambiguous associated type
-  --> $DIR/bad-assoc-ty.rs:34:10
+  --> $DIR/bad-assoc-ty.rs:33:10
    |
 LL | type H = Fn(u8) -> (u8)::Output;
    |          ^^^^^^^^^^^^^^^^^^^^^^ help: use fully-qualified syntax: `<(dyn std::ops::Fn(u8) -> u8 + 'static) as Trait>::Output`
 
 error[E0223]: ambiguous associated type
-  --> $DIR/bad-assoc-ty.rs:38:19
+  --> $DIR/bad-assoc-ty.rs:37:19
    |
 LL |     ($ty: ty) => ($ty::AssocTy);
    |                   ^^^^^^^^^^^^ help: use fully-qualified syntax: `<u8 as Trait>::AssocTy`
@@ -123,11 +117,19 @@ LL | type J = ty!(u8);
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0223]: ambiguous associated type
-  --> $DIR/bad-assoc-ty.rs:45:10
+  --> $DIR/bad-assoc-ty.rs:44:10
    |
 LL | type I = ty!()::AssocTy;
    |          ^^^^^^^^^^^^^^ help: use fully-qualified syntax: `<u8 as Trait>::AssocTy`
 
+error[E0121]: the type placeholder `_` is not allowed within types on item signatures
+  --> $DIR/bad-assoc-ty.rs:49:13
+   |
+LL | fn foo<X: K<_, _>>(x: X) {}
+   |             ^  ^ not allowed in type signatures
+   |             |
+   |             not allowed in type signatures
+
 error: aborting due to 20 previous errors
 
 Some errors have detailed explanations: E0121, E0223.
diff --git a/src/test/ui/self/self-infer.rs b/src/test/ui/self/self-infer.rs
index 77c80521236a0..0956f2a56918c 100644
--- a/src/test/ui/self/self-infer.rs
+++ b/src/test/ui/self/self-infer.rs
@@ -2,9 +2,7 @@ struct S;
 
 impl S {
     fn f(self: _) {} //~ERROR the type placeholder `_` is not allowed within types on item sig
-    //~^ ERROR the type placeholder `_` is not allowed within types on item sig
     fn g(self: &_) {} //~ERROR the type placeholder `_` is not allowed within types on item sig
-    //~^ ERROR the type placeholder `_` is not allowed within types on item sig
 }
 
 fn main() {}
diff --git a/src/test/ui/self/self-infer.stderr b/src/test/ui/self/self-infer.stderr
index d6bf8b44d6099..1475b212b56a6 100644
--- a/src/test/ui/self/self-infer.stderr
+++ b/src/test/ui/self/self-infer.stderr
@@ -1,9 +1,3 @@
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/self-infer.rs:4:16
-   |
-LL |     fn f(self: _) {}
-   |                ^ not allowed in type signatures
-
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
   --> $DIR/self-infer.rs:4:16
    |
@@ -16,13 +10,7 @@ LL |     fn f<T>(self: T) {}
    |         ^^^       ^
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/self-infer.rs:6:17
-   |
-LL |     fn g(self: &_) {}
-   |                 ^ not allowed in type signatures
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/self-infer.rs:6:17
+  --> $DIR/self-infer.rs:5:17
    |
 LL |     fn g(self: &_) {}
    |                 ^ not allowed in type signatures
@@ -32,6 +20,6 @@ help: use type parameters instead
 LL |     fn g<T>(self: &T) {}
    |         ^^^        ^
 
-error: aborting due to 4 previous errors
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0121`.
diff --git a/src/test/ui/typeck/typeck_type_placeholder_item.rs b/src/test/ui/typeck/typeck_type_placeholder_item.rs
index eb6cc832fb417..6cd2b8c75b639 100644
--- a/src/test/ui/typeck/typeck_type_placeholder_item.rs
+++ b/src/test/ui/typeck/typeck_type_placeholder_item.rs
@@ -1,4 +1,5 @@
-#![feature(type_alias_impl_trait)] // Needed for single test `type Y = impl Trait<_>`
+// Needed for `type Y = impl Trait<_>` and `type B = _;`
+#![feature(type_alias_impl_trait, associated_type_defaults)]
 // This test checks that it is not possible to enable global type
 // inference by using the `_` type placeholder.
 
@@ -19,24 +20,19 @@ static TEST5: (_, _) = (1, 2);
 
 fn test6(_: _) { }
 //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
-//~| ERROR the type placeholder `_` is not allowed within types on item signatures
 
 fn test6_b<T>(_: _, _: T) { }
 //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
-//~| ERROR the type placeholder `_` is not allowed within types on item signatures
 
 fn test6_c<T, K, L, A, B>(_: _, _: (T, K, L, A, B)) { }
 //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
-//~| ERROR the type placeholder `_` is not allowed within types on item signatures
 
 fn test7(x: _) { let _x: usize = x; }
 //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
-//~| ERROR the type placeholder `_` is not allowed within types on item signatures
 
 fn test8(_f: fn() -> _) { }
 //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
 //~| ERROR the type placeholder `_` is not allowed within types on item signatures
-//~| ERROR the type placeholder `_` is not allowed within types on item signatures
 
 struct Test9;
 
@@ -46,7 +42,6 @@ impl Test9 {
 
     fn test10(&self, _x : _) { }
     //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
-    //~| ERROR the type placeholder `_` is not allowed within types on item signatures
 }
 
 fn test11(x: &usize) -> &_ {
@@ -65,16 +60,12 @@ impl Clone for Test9 {
 
     fn clone_from(&mut self, other: _) { *self = Test9; }
     //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
-    //~| ERROR the type placeholder `_` is not allowed within types on item signatures
 }
 
 struct Test10 {
     a: _,
     //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
-    //~| ERROR the type placeholder `_` is not allowed within types on item signatures
     b: (_, _),
-    //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
-    //~| ERROR the type placeholder `_` is not allowed within types on item signatures
 }
 
 pub fn main() {
@@ -102,16 +93,13 @@ pub fn main() {
 
     fn fn_test6(_: _) { }
     //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
-    //~| ERROR the type placeholder `_` is not allowed within types on item signatures
 
     fn fn_test7(x: _) { let _x: usize = x; }
     //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
-    //~| ERROR the type placeholder `_` is not allowed within types on item signatures
 
     fn fn_test8(_f: fn() -> _) { }
     //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
     //~| ERROR the type placeholder `_` is not allowed within types on item signatures
-    //~| ERROR the type placeholder `_` is not allowed within types on item signatures
 
     struct FnTest9;
 
@@ -121,7 +109,6 @@ pub fn main() {
 
         fn fn_test10(&self, _x : _) { }
         //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
-        //~| ERROR the type placeholder `_` is not allowed within types on item signatures
     }
 
     impl Clone for FnTest9 {
@@ -130,16 +117,12 @@ pub fn main() {
 
         fn clone_from(&mut self, other: _) { *self = FnTest9; }
         //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
-        //~| ERROR the type placeholder `_` is not allowed within types on item signatures
     }
 
     struct FnTest10 {
         a: _,
         //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
-        //~| ERROR the type placeholder `_` is not allowed within types on item signatures
         b: (_, _),
-        //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
-        //~| ERROR the type placeholder `_` is not allowed within types on item signatures
     }
 
     fn fn_test11(_: _) -> (_, _) { panic!() }
@@ -156,30 +139,21 @@ pub fn main() {
 trait T {
     fn method_test1(&self, x: _);
     //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
-    //~| ERROR the type placeholder `_` is not allowed within types on item signatures
     fn method_test2(&self, x: _) -> _;
     //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
-    //~| ERROR the type placeholder `_` is not allowed within types on item signatures
-    //~| ERROR the type placeholder `_` is not allowed within types on item signatures
     fn method_test3(&self) -> _;
     //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
-    //~| ERROR the type placeholder `_` is not allowed within types on item signatures
     fn assoc_fn_test1(x: _);
     //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
-    //~| ERROR the type placeholder `_` is not allowed within types on item signatures
     fn assoc_fn_test2(x: _) -> _;
     //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
-    //~| ERROR the type placeholder `_` is not allowed within types on item signatures
-    //~| ERROR the type placeholder `_` is not allowed within types on item signatures
     fn assoc_fn_test3() -> _;
     //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
-    //~| ERROR the type placeholder `_` is not allowed within types on item signatures
 }
 
 struct BadStruct<_>(_);
 //~^ ERROR expected identifier, found reserved identifier `_`
 //~| ERROR the type placeholder `_` is not allowed within types on item signatures
-//~| ERROR the type placeholder `_` is not allowed within types on item signatures
 trait BadTrait<_> {}
 //~^ ERROR expected identifier, found reserved identifier `_`
 impl BadTrait<_> for BadStruct<_> {}
@@ -198,11 +172,9 @@ struct BadStruct1<_, _>(_);
 //~| ERROR expected identifier, found reserved identifier `_`
 //~| ERROR the name `_` is already used
 //~| ERROR the type placeholder `_` is not allowed within types on item signatures
-//~| ERROR the type placeholder `_` is not allowed within types on item signatures
 struct BadStruct2<_, T>(_, T);
 //~^ ERROR expected identifier, found reserved identifier `_`
 //~| ERROR the type placeholder `_` is not allowed within types on item signatures
-//~| ERROR the type placeholder `_` is not allowed within types on item signatures
 
 type X = Box<_>;
 //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
@@ -217,3 +189,25 @@ type Y = impl Trait<_>;
 fn foo() -> Y {
     Struct
 }
+
+trait Qux {
+    type A;
+    type B = _;
+    //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+    const C: _;
+    //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+    const D: _ = 42;
+    //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+    // type E: _; // FIXME: make the parser propagate the existence of `B`
+}
+impl Qux for Struct {
+    type A = _;
+    //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+    type B = _;
+    //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+    const C: _;
+    //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+    //~| ERROR associated constant in `impl` without body
+    const D: _ = 42;
+    //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+}
diff --git a/src/test/ui/typeck/typeck_type_placeholder_item.stderr b/src/test/ui/typeck/typeck_type_placeholder_item.stderr
index a8fdd66ee3753..f2d02f70f4a66 100644
--- a/src/test/ui/typeck/typeck_type_placeholder_item.stderr
+++ b/src/test/ui/typeck/typeck_type_placeholder_item.stderr
@@ -1,35 +1,43 @@
 error: expected identifier, found reserved identifier `_`
-  --> $DIR/typeck_type_placeholder_item.rs:179:18
+  --> $DIR/typeck_type_placeholder_item.rs:154:18
    |
 LL | struct BadStruct<_>(_);
    |                  ^ expected identifier, found reserved identifier
 
 error: expected identifier, found reserved identifier `_`
-  --> $DIR/typeck_type_placeholder_item.rs:183:16
+  --> $DIR/typeck_type_placeholder_item.rs:157:16
    |
 LL | trait BadTrait<_> {}
    |                ^ expected identifier, found reserved identifier
 
 error: expected identifier, found reserved identifier `_`
-  --> $DIR/typeck_type_placeholder_item.rs:196:19
+  --> $DIR/typeck_type_placeholder_item.rs:170:19
    |
 LL | struct BadStruct1<_, _>(_);
    |                   ^ expected identifier, found reserved identifier
 
 error: expected identifier, found reserved identifier `_`
-  --> $DIR/typeck_type_placeholder_item.rs:196:22
+  --> $DIR/typeck_type_placeholder_item.rs:170:22
    |
 LL | struct BadStruct1<_, _>(_);
    |                      ^ expected identifier, found reserved identifier
 
 error: expected identifier, found reserved identifier `_`
-  --> $DIR/typeck_type_placeholder_item.rs:202:19
+  --> $DIR/typeck_type_placeholder_item.rs:175:19
    |
 LL | struct BadStruct2<_, T>(_, T);
    |                   ^ expected identifier, found reserved identifier
 
+error: associated constant in `impl` without body
+  --> $DIR/typeck_type_placeholder_item.rs:208:5
+   |
+LL |     const C: _;
+   |     ^^^^^^^^^^-
+   |               |
+   |               help: provide a definition for the constant: `= <expr>;`
+
 error[E0403]: the name `_` is already used for a generic parameter in this item's generic parameters
-  --> $DIR/typeck_type_placeholder_item.rs:196:22
+  --> $DIR/typeck_type_placeholder_item.rs:170:22
    |
 LL | struct BadStruct1<_, _>(_);
    |                   -  ^ already used
@@ -37,7 +45,7 @@ LL | struct BadStruct1<_, _>(_);
    |                   first use of `_`
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:5:14
+  --> $DIR/typeck_type_placeholder_item.rs:6:14
    |
 LL | fn test() -> _ { 5 }
    |              ^
@@ -46,7 +54,7 @@ LL | fn test() -> _ { 5 }
    |              help: replace with the correct return type: `i32`
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:8:16
+  --> $DIR/typeck_type_placeholder_item.rs:9:16
    |
 LL | fn test2() -> (_, _) { (5, 5) }
    |               -^--^-
@@ -56,7 +64,7 @@ LL | fn test2() -> (_, _) { (5, 5) }
    |               help: replace with the correct return type: `(i32, i32)`
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:11:15
+  --> $DIR/typeck_type_placeholder_item.rs:12:15
    |
 LL | static TEST3: _ = "test";
    |               ^
@@ -65,7 +73,7 @@ LL | static TEST3: _ = "test";
    |               help: replace `_` with the correct type: `&'static str`
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:14:15
+  --> $DIR/typeck_type_placeholder_item.rs:15:15
    |
 LL | static TEST4: _ = 145;
    |               ^
@@ -74,19 +82,13 @@ LL | static TEST4: _ = 145;
    |               help: replace `_` with the correct type: `i32`
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:17:15
+  --> $DIR/typeck_type_placeholder_item.rs:18:15
    |
 LL | static TEST5: (_, _) = (1, 2);
    |               ^^^^^^ not allowed in type signatures
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:20:13
-   |
-LL | fn test6(_: _) { }
-   |             ^ not allowed in type signatures
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:20:13
+  --> $DIR/typeck_type_placeholder_item.rs:21:13
    |
 LL | fn test6(_: _) { }
    |             ^ not allowed in type signatures
@@ -96,12 +98,6 @@ help: use type parameters instead
 LL | fn test6<T>(_: T) { }
    |         ^^^    ^
 
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:24:18
-   |
-LL | fn test6_b<T>(_: _, _: T) { }
-   |                  ^ not allowed in type signatures
-
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
   --> $DIR/typeck_type_placeholder_item.rs:24:18
    |
@@ -114,13 +110,7 @@ LL | fn test6_b<T, K>(_: K, _: T) { }
    |             ^^^     ^
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:28:30
-   |
-LL | fn test6_c<T, K, L, A, B>(_: _, _: (T, K, L, A, B)) { }
-   |                              ^ not allowed in type signatures
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:28:30
+  --> $DIR/typeck_type_placeholder_item.rs:27:30
    |
 LL | fn test6_c<T, K, L, A, B>(_: _, _: (T, K, L, A, B)) { }
    |                              ^ not allowed in type signatures
@@ -131,13 +121,7 @@ LL | fn test6_c<T, K, L, A, B, C>(_: C, _: (T, K, L, A, B)) { }
    |                         ^^^     ^
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:32:13
-   |
-LL | fn test7(x: _) { let _x: usize = x; }
-   |             ^ not allowed in type signatures
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:32:13
+  --> $DIR/typeck_type_placeholder_item.rs:30:13
    |
 LL | fn test7(x: _) { let _x: usize = x; }
    |             ^ not allowed in type signatures
@@ -148,19 +132,13 @@ LL | fn test7<T>(x: T) { let _x: usize = x; }
    |         ^^^    ^
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:36:22
+  --> $DIR/typeck_type_placeholder_item.rs:33:22
    |
 LL | fn test8(_f: fn() -> _) { }
    |                      ^ not allowed in type signatures
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:36:22
-   |
-LL | fn test8(_f: fn() -> _) { }
-   |                      ^ not allowed in type signatures
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:36:22
+  --> $DIR/typeck_type_placeholder_item.rs:33:22
    |
 LL | fn test8(_f: fn() -> _) { }
    |                      ^ not allowed in type signatures
@@ -171,61 +149,7 @@ LL | fn test8<T>(_f: fn() -> T) { }
    |         ^^^             ^
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:72:8
-   |
-LL |     a: _,
-   |        ^ not allowed in type signatures
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:75:9
-   |
-LL |     b: (_, _),
-   |         ^ not allowed in type signatures
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:75:12
-   |
-LL |     b: (_, _),
-   |            ^ not allowed in type signatures
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:137:12
-   |
-LL |         a: _,
-   |            ^ not allowed in type signatures
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:140:13
-   |
-LL |         b: (_, _),
-   |             ^ not allowed in type signatures
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:140:16
-   |
-LL |         b: (_, _),
-   |                ^ not allowed in type signatures
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:179:21
-   |
-LL | struct BadStruct<_>(_);
-   |                     ^ not allowed in type signatures
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:196:25
-   |
-LL | struct BadStruct1<_, _>(_);
-   |                         ^ not allowed in type signatures
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:202:25
-   |
-LL | struct BadStruct2<_, T>(_, T);
-   |                         ^ not allowed in type signatures
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:52:26
+  --> $DIR/typeck_type_placeholder_item.rs:47:26
    |
 LL | fn test11(x: &usize) -> &_ {
    |                         -^
@@ -234,7 +158,7 @@ LL | fn test11(x: &usize) -> &_ {
    |                         help: replace with the correct return type: `&&usize`
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:57:52
+  --> $DIR/typeck_type_placeholder_item.rs:52:52
    |
 LL | unsafe fn test12(x: *const usize) -> *const *const _ {
    |                                      --------------^
@@ -243,11 +167,11 @@ LL | unsafe fn test12(x: *const usize) -> *const *const _ {
    |                                      help: replace with the correct return type: `*const *const usize`
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:72:8
+  --> $DIR/typeck_type_placeholder_item.rs:66:8
    |
 LL |     a: _,
    |        ^ not allowed in type signatures
-...
+LL |
 LL |     b: (_, _),
    |         ^  ^ not allowed in type signatures
    |         |
@@ -258,18 +182,17 @@ help: use type parameters instead
 LL | struct Test10<T> {
 LL |     a: T,
 LL |
-LL |
 LL |     b: (T, T),
    |
 
 error: missing type for `static` item
-  --> $DIR/typeck_type_placeholder_item.rs:81:12
+  --> $DIR/typeck_type_placeholder_item.rs:72:12
    |
 LL |     static A = 42;
    |            ^ help: provide a type for the item: `A: i32`
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:83:15
+  --> $DIR/typeck_type_placeholder_item.rs:74:15
    |
 LL |     static B: _ = 42;
    |               ^
@@ -278,13 +201,13 @@ LL |     static B: _ = 42;
    |               help: replace `_` with the correct type: `i32`
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:85:15
+  --> $DIR/typeck_type_placeholder_item.rs:76:15
    |
 LL |     static C: Option<_> = Some(42);
    |               ^^^^^^^^^ not allowed in type signatures
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:88:21
+  --> $DIR/typeck_type_placeholder_item.rs:79:21
    |
 LL |     fn fn_test() -> _ { 5 }
    |                     ^
@@ -293,7 +216,7 @@ LL |     fn fn_test() -> _ { 5 }
    |                     help: replace with the correct return type: `i32`
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:91:23
+  --> $DIR/typeck_type_placeholder_item.rs:82:23
    |
 LL |     fn fn_test2() -> (_, _) { (5, 5) }
    |                      -^--^-
@@ -303,7 +226,7 @@ LL |     fn fn_test2() -> (_, _) { (5, 5) }
    |                      help: replace with the correct return type: `(i32, i32)`
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:94:22
+  --> $DIR/typeck_type_placeholder_item.rs:85:22
    |
 LL |     static FN_TEST3: _ = "test";
    |                      ^
@@ -312,7 +235,7 @@ LL |     static FN_TEST3: _ = "test";
    |                      help: replace `_` with the correct type: `&'static str`
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:97:22
+  --> $DIR/typeck_type_placeholder_item.rs:88:22
    |
 LL |     static FN_TEST4: _ = 145;
    |                      ^
@@ -321,19 +244,13 @@ LL |     static FN_TEST4: _ = 145;
    |                      help: replace `_` with the correct type: `i32`
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:100:22
+  --> $DIR/typeck_type_placeholder_item.rs:91:22
    |
 LL |     static FN_TEST5: (_, _) = (1, 2);
    |                      ^^^^^^ not allowed in type signatures
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:103:20
-   |
-LL |     fn fn_test6(_: _) { }
-   |                    ^ not allowed in type signatures
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:103:20
+  --> $DIR/typeck_type_placeholder_item.rs:94:20
    |
 LL |     fn fn_test6(_: _) { }
    |                    ^ not allowed in type signatures
@@ -344,13 +261,7 @@ LL |     fn fn_test6<T>(_: T) { }
    |                ^^^    ^
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:107:20
-   |
-LL |     fn fn_test7(x: _) { let _x: usize = x; }
-   |                    ^ not allowed in type signatures
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:107:20
+  --> $DIR/typeck_type_placeholder_item.rs:97:20
    |
 LL |     fn fn_test7(x: _) { let _x: usize = x; }
    |                    ^ not allowed in type signatures
@@ -361,19 +272,13 @@ LL |     fn fn_test7<T>(x: T) { let _x: usize = x; }
    |                ^^^    ^
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:111:29
+  --> $DIR/typeck_type_placeholder_item.rs:100:29
    |
 LL |     fn fn_test8(_f: fn() -> _) { }
    |                             ^ not allowed in type signatures
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:111:29
-   |
-LL |     fn fn_test8(_f: fn() -> _) { }
-   |                             ^ not allowed in type signatures
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:111:29
+  --> $DIR/typeck_type_placeholder_item.rs:100:29
    |
 LL |     fn fn_test8(_f: fn() -> _) { }
    |                             ^ not allowed in type signatures
@@ -384,11 +289,11 @@ LL |     fn fn_test8<T>(_f: fn() -> T) { }
    |                ^^^             ^
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:137:12
+  --> $DIR/typeck_type_placeholder_item.rs:123:12
    |
 LL |         a: _,
    |            ^ not allowed in type signatures
-...
+LL |
 LL |         b: (_, _),
    |             ^  ^ not allowed in type signatures
    |             |
@@ -399,18 +304,17 @@ help: use type parameters instead
 LL |     struct FnTest10<T> {
 LL |         a: T,
 LL |
-LL |
 LL |         b: (T, T),
    |
 
 error[E0282]: type annotations needed
-  --> $DIR/typeck_type_placeholder_item.rs:145:18
+  --> $DIR/typeck_type_placeholder_item.rs:128:18
    |
 LL |     fn fn_test11(_: _) -> (_, _) { panic!() }
    |                  ^ cannot infer type
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:145:28
+  --> $DIR/typeck_type_placeholder_item.rs:128:28
    |
 LL |     fn fn_test11(_: _) -> (_, _) { panic!() }
    |                            ^  ^ not allowed in type signatures
@@ -418,7 +322,7 @@ LL |     fn fn_test11(_: _) -> (_, _) { panic!() }
    |                            not allowed in type signatures
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:149:30
+  --> $DIR/typeck_type_placeholder_item.rs:132:30
    |
 LL |     fn fn_test12(x: i32) -> (_, _) { (x, x) }
    |                             -^--^-
@@ -428,7 +332,7 @@ LL |     fn fn_test12(x: i32) -> (_, _) { (x, x) }
    |                             help: replace with the correct return type: `(i32, i32)`
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:152:33
+  --> $DIR/typeck_type_placeholder_item.rs:135:33
    |
 LL |     fn fn_test13(x: _) -> (i32, _) { (x, x) }
    |                           ------^-
@@ -437,7 +341,7 @@ LL |     fn fn_test13(x: _) -> (i32, _) { (x, x) }
    |                           help: replace with the correct return type: `(i32, i32)`
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:179:21
+  --> $DIR/typeck_type_placeholder_item.rs:154:21
    |
 LL | struct BadStruct<_>(_);
    |                     ^ not allowed in type signatures
@@ -448,19 +352,19 @@ LL | struct BadStruct<T>(T);
    |                  ^  ^
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:185:32
+  --> $DIR/typeck_type_placeholder_item.rs:159:32
    |
 LL | impl BadTrait<_> for BadStruct<_> {}
    |                                ^ not allowed in type signatures
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:185:15
+  --> $DIR/typeck_type_placeholder_item.rs:159:15
    |
 LL | impl BadTrait<_> for BadStruct<_> {}
    |               ^ not allowed in type signatures
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:185:15
+  --> $DIR/typeck_type_placeholder_item.rs:159:15
    |
 LL | impl BadTrait<_> for BadStruct<_> {}
    |               ^                ^ not allowed in type signatures
@@ -473,13 +377,13 @@ LL | impl<T> BadTrait<T> for BadStruct<T> {}
    |     ^^^          ^                ^
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:190:34
+  --> $DIR/typeck_type_placeholder_item.rs:164:34
    |
 LL | fn impl_trait() -> impl BadTrait<_> {
    |                                  ^ not allowed in type signatures
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:196:25
+  --> $DIR/typeck_type_placeholder_item.rs:170:25
    |
 LL | struct BadStruct1<_, _>(_);
    |                         ^ not allowed in type signatures
@@ -490,7 +394,7 @@ LL | struct BadStruct1<T, _>(T);
    |                   ^     ^
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:202:25
+  --> $DIR/typeck_type_placeholder_item.rs:175:25
    |
 LL | struct BadStruct2<_, T>(_, T);
    |                         ^ not allowed in type signatures
@@ -501,25 +405,19 @@ LL | struct BadStruct2<K, T>(K, T);
    |                   ^     ^
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:207:14
+  --> $DIR/typeck_type_placeholder_item.rs:179:14
    |
 LL | type X = Box<_>;
    |              ^ not allowed in type signatures
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:207:14
+  --> $DIR/typeck_type_placeholder_item.rs:179:14
    |
 LL | type X = Box<_>;
    |              ^ not allowed in type signatures
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:47:27
-   |
-LL |     fn test10(&self, _x : _) { }
-   |                           ^ not allowed in type signatures
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:47:27
+  --> $DIR/typeck_type_placeholder_item.rs:43:27
    |
 LL |     fn test10(&self, _x : _) { }
    |                           ^ not allowed in type signatures
@@ -530,13 +428,7 @@ LL |     fn test10<T>(&self, _x : T) { }
    |              ^^^             ^
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:157:31
-   |
-LL |     fn method_test1(&self, x: _);
-   |                               ^ not allowed in type signatures
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:157:31
+  --> $DIR/typeck_type_placeholder_item.rs:140:31
    |
 LL |     fn method_test1(&self, x: _);
    |                               ^ not allowed in type signatures
@@ -547,19 +439,7 @@ LL |     fn method_test1<T>(&self, x: T);
    |                    ^^^           ^
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:160:37
-   |
-LL |     fn method_test2(&self, x: _) -> _;
-   |                                     ^ not allowed in type signatures
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:160:31
-   |
-LL |     fn method_test2(&self, x: _) -> _;
-   |                               ^ not allowed in type signatures
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:160:31
+  --> $DIR/typeck_type_placeholder_item.rs:142:31
    |
 LL |     fn method_test2(&self, x: _) -> _;
    |                               ^     ^ not allowed in type signatures
@@ -572,13 +452,7 @@ LL |     fn method_test2<T>(&self, x: T) -> T;
    |                    ^^^           ^     ^
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:164:31
-   |
-LL |     fn method_test3(&self) -> _;
-   |                               ^ not allowed in type signatures
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:164:31
+  --> $DIR/typeck_type_placeholder_item.rs:144:31
    |
 LL |     fn method_test3(&self) -> _;
    |                               ^ not allowed in type signatures
@@ -589,13 +463,7 @@ LL |     fn method_test3<T>(&self) -> T;
    |                    ^^^           ^
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:167:26
-   |
-LL |     fn assoc_fn_test1(x: _);
-   |                          ^ not allowed in type signatures
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:167:26
+  --> $DIR/typeck_type_placeholder_item.rs:146:26
    |
 LL |     fn assoc_fn_test1(x: _);
    |                          ^ not allowed in type signatures
@@ -606,19 +474,7 @@ LL |     fn assoc_fn_test1<T>(x: T);
    |                      ^^^    ^
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:170:32
-   |
-LL |     fn assoc_fn_test2(x: _) -> _;
-   |                                ^ not allowed in type signatures
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:170:26
-   |
-LL |     fn assoc_fn_test2(x: _) -> _;
-   |                          ^ not allowed in type signatures
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:170:26
+  --> $DIR/typeck_type_placeholder_item.rs:148:26
    |
 LL |     fn assoc_fn_test2(x: _) -> _;
    |                          ^     ^ not allowed in type signatures
@@ -631,13 +487,7 @@ LL |     fn assoc_fn_test2<T>(x: T) -> T;
    |                      ^^^    ^     ^
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:174:28
-   |
-LL |     fn assoc_fn_test3() -> _;
-   |                            ^ not allowed in type signatures
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:174:28
+  --> $DIR/typeck_type_placeholder_item.rs:150:28
    |
 LL |     fn assoc_fn_test3() -> _;
    |                            ^ not allowed in type signatures
@@ -648,13 +498,7 @@ LL |     fn assoc_fn_test3<T>() -> T;
    |                      ^^^      ^
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:66:37
-   |
-LL |     fn clone_from(&mut self, other: _) { *self = Test9; }
-   |                                     ^ not allowed in type signatures
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:66:37
+  --> $DIR/typeck_type_placeholder_item.rs:61:37
    |
 LL |     fn clone_from(&mut self, other: _) { *self = Test9; }
    |                                     ^ not allowed in type signatures
@@ -665,13 +509,7 @@ LL |     fn clone_from<T>(&mut self, other: T) { *self = Test9; }
    |                  ^^^                   ^
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:122:34
-   |
-LL |         fn fn_test10(&self, _x : _) { }
-   |                                  ^ not allowed in type signatures
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:122:34
+  --> $DIR/typeck_type_placeholder_item.rs:110:34
    |
 LL |         fn fn_test10(&self, _x : _) { }
    |                                  ^ not allowed in type signatures
@@ -682,13 +520,7 @@ LL |         fn fn_test10<T>(&self, _x : T) { }
    |                     ^^^             ^
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:131:41
-   |
-LL |         fn clone_from(&mut self, other: _) { *self = FnTest9; }
-   |                                         ^ not allowed in type signatures
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:131:41
+  --> $DIR/typeck_type_placeholder_item.rs:118:41
    |
 LL |         fn clone_from(&mut self, other: _) { *self = FnTest9; }
    |                                         ^ not allowed in type signatures
@@ -699,25 +531,46 @@ LL |         fn clone_from<T>(&mut self, other: T) { *self = FnTest9; }
    |                      ^^^                   ^
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:190:34
+  --> $DIR/typeck_type_placeholder_item.rs:164:34
    |
 LL | fn impl_trait() -> impl BadTrait<_> {
    |                                  ^ not allowed in type signatures
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:214:21
+  --> $DIR/typeck_type_placeholder_item.rs:186:21
    |
 LL | type Y = impl Trait<_>;
    |                     ^ not allowed in type signatures
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:214:21
+  --> $DIR/typeck_type_placeholder_item.rs:186:21
    |
 LL | type Y = impl Trait<_>;
    |                     ^ not allowed in type signatures
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:44:24
+  --> $DIR/typeck_type_placeholder_item.rs:195:14
+   |
+LL |     type B = _;
+   |              ^ not allowed in type signatures
+
+error[E0121]: the type placeholder `_` is not allowed within types on item signatures
+  --> $DIR/typeck_type_placeholder_item.rs:197:14
+   |
+LL |     const C: _;
+   |              ^ not allowed in type signatures
+
+error[E0121]: the type placeholder `_` is not allowed within types on item signatures
+  --> $DIR/typeck_type_placeholder_item.rs:199:14
+   |
+LL |     const D: _ = 42;
+   |              ^
+   |              |
+   |              not allowed in type signatures
+   |              help: replace `_` with the correct type: `i32`
+
+error[E0121]: the type placeholder `_` is not allowed within types on item signatures
+  --> $DIR/typeck_type_placeholder_item.rs:40:24
    |
 LL |     fn test9(&self) -> _ { () }
    |                        ^
@@ -726,7 +579,7 @@ LL |     fn test9(&self) -> _ { () }
    |                        help: replace with the correct return type: `()`
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:63:24
+  --> $DIR/typeck_type_placeholder_item.rs:58:24
    |
 LL |     fn clone(&self) -> _ { Test9 }
    |                        ^
@@ -735,7 +588,7 @@ LL |     fn clone(&self) -> _ { Test9 }
    |                        help: replace with the correct return type: `Test9`
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:119:31
+  --> $DIR/typeck_type_placeholder_item.rs:107:31
    |
 LL |         fn fn_test9(&self) -> _ { () }
    |                               ^
@@ -744,7 +597,7 @@ LL |         fn fn_test9(&self) -> _ { () }
    |                               help: replace with the correct return type: `()`
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:128:28
+  --> $DIR/typeck_type_placeholder_item.rs:115:28
    |
 LL |         fn clone(&self) -> _ { FnTest9 }
    |                            ^
@@ -752,7 +605,34 @@ LL |         fn clone(&self) -> _ { FnTest9 }
    |                            not allowed in type signatures
    |                            help: replace with the correct return type: `main::FnTest9`
 
-error: aborting due to 92 previous errors
+error[E0121]: the type placeholder `_` is not allowed within types on item signatures
+  --> $DIR/typeck_type_placeholder_item.rs:204:14
+   |
+LL |     type A = _;
+   |              ^ not allowed in type signatures
+
+error[E0121]: the type placeholder `_` is not allowed within types on item signatures
+  --> $DIR/typeck_type_placeholder_item.rs:206:14
+   |
+LL |     type B = _;
+   |              ^ not allowed in type signatures
+
+error[E0121]: the type placeholder `_` is not allowed within types on item signatures
+  --> $DIR/typeck_type_placeholder_item.rs:208:14
+   |
+LL |     const C: _;
+   |              ^ not allowed in type signatures
+
+error[E0121]: the type placeholder `_` is not allowed within types on item signatures
+  --> $DIR/typeck_type_placeholder_item.rs:211:14
+   |
+LL |     const D: _ = 42;
+   |              ^
+   |              |
+   |              not allowed in type signatures
+   |              help: replace `_` with the correct type: `i32`
+
+error: aborting due to 71 previous errors
 
 Some errors have detailed explanations: E0121, E0282, E0403.
 For more information about an error, try `rustc --explain E0121`.