Correctly resolve Inherent Associated Types

Author: fee1-dead

compiler/rustc_hir_analysis/src/astconv/mod.rs

@@ -1910,6 +1910,20 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                     }
                 }
             }
+
+            // see if we can satisfy using an inherent associated type
+            for impl_ in tcx.inherent_impls(adt_def.did()) {
+                let assoc_ty = tcx.associated_items(impl_).find_by_name_and_kind(
+                    tcx,
+                    assoc_ident,
+                    ty::AssocKind::Type,
+                    *impl_,
+                );
+                if let Some(assoc_ty) = assoc_ty {
+                    let ty = tcx.type_of(assoc_ty.def_id);
+                    return Ok((ty, DefKind::AssocTy, assoc_ty.def_id));
+                }
+            }
         }
 
         // Find the type of the associated item, and the trait where the associated

src/test/ui/assoc-inherent.rs

@@ -0,0 +1,10 @@
+#![feature(inherent_associated_types)]
+#![allow(incomplete_features)]
+
+struct Foo;
+
+impl Foo {
+    type Baz; //~ ERROR associated type in `impl` without body
+}
+
+fn main() {}

src/test/ui/assoc-inherent.stderr

@@ -0,0 +1,10 @@
+error: associated type in `impl` without body
+  --> $DIR/assoc-inherent-no-body.rs:7:5
+   |
+LL |     type Baz;
+   |     ^^^^^^^^-
+   |             |
+   |             help: provide a definition for the type: `= <type>;`
+
+error: aborting due to previous error
+

src/test/ui/associated-inherent-types/assoc-inherent-no-body.rs

@@ -0,0 +1,14 @@
+// check-pass
+#![feature(inherent_associated_types)]
+#![allow(incomplete_features)]
+
+struct Foo;
+
+impl Foo {
+    type Bar = isize;
+}
+
+fn main() {
+    let x: Foo::Bar;
+    x = 0isize;
+}

src/test/ui/associated-inherent-types/assoc-inherent-no-body.stderr

@@ -1,40 +1,40 @@
 error: `Self` is not valid in the self type of an impl block
-  --> $DIR/resolve-self-in-impl.rs:14:13
+  --> $DIR/resolve-self-in-impl.rs:16:6
    |
-LL | impl Tr for Self {}
-   |             ^^^^
+LL | impl Self {}
+   |      ^^^^
    |
    = note: replace `Self` with a different type
 
 error: `Self` is not valid in the self type of an impl block
-  --> $DIR/resolve-self-in-impl.rs:15:15
+  --> $DIR/resolve-self-in-impl.rs:17:8
    |
-LL | impl Tr for S<Self> {}
-   |               ^^^^
+LL | impl S<Self> {}
+   |        ^^^^
    |
    = note: replace `Self` with a different type
 
 error: `Self` is not valid in the self type of an impl block
-  --> $DIR/resolve-self-in-impl.rs:16:6
+  --> $DIR/resolve-self-in-impl.rs:18:7
    |
-LL | impl Self {}
-   |      ^^^^
+LL | impl (Self, Self) {}
+   |       ^^^^  ^^^^
    |
    = note: replace `Self` with a different type
 
 error: `Self` is not valid in the self type of an impl block
-  --> $DIR/resolve-self-in-impl.rs:17:8
+  --> $DIR/resolve-self-in-impl.rs:14:13
    |
-LL | impl S<Self> {}
-   |        ^^^^
+LL | impl Tr for Self {}
+   |             ^^^^
    |
    = note: replace `Self` with a different type
 
 error: `Self` is not valid in the self type of an impl block
-  --> $DIR/resolve-self-in-impl.rs:18:7
+  --> $DIR/resolve-self-in-impl.rs:15:15
    |
-LL | impl (Self, Self) {}
-   |       ^^^^  ^^^^
+LL | impl Tr for S<Self> {}
+   |               ^^^^
    |
    = note: replace `Self` with a different type