Don't ICE for completely unexpandable impl Trait types

src/librustc_typeck/check/writeback.rs

@@ -479,10 +479,12 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
             let mut skip_add = false;
 
             if let ty::Opaque(defin_ty_def_id, _substs) = definition_ty.kind {
-                if def_id == defin_ty_def_id {
-                    debug!("Skipping adding concrete definition for opaque type {:?} {:?}",
-                           opaque_defn, defin_ty_def_id);
-                    skip_add = true;
+                if let hir::OpaqueTyOrigin::TypeAlias = opaque_defn.origin {
+                    if def_id == defin_ty_def_id {
+                        debug!("Skipping adding concrete definition for opaque type {:?} {:?}",
+                               opaque_defn, defin_ty_def_id);
+                        skip_add = true;
+                    }
                 }
             }
 

src/test/ui/impl-trait/recursive-impl-trait-type-direct.rs

@@ -0,0 +1,7 @@
+// Test that an impl trait type that expands to itself is an error.
+
+fn test() -> impl Sized {       //~ ERROR E0720
+    test()
+}
+
+fn main() {}

src/test/ui/impl-trait/recursive-impl-trait-type-direct.stderr

@@ -0,0 +1,11 @@
+error[E0720]: opaque type expands to a recursive type
+  --> $DIR/recursive-impl-trait-type-direct.rs:3:14
+   |
+LL | fn test() -> impl Sized {
+   |              ^^^^^^^^^^ expands to a recursive type
+   |
+   = note: type resolves to itself
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0720`.

src/test/ui/impl-trait/recursive-impl-trait-type.stderr → src/test/ui/impl-trait/recursive-impl-trait-type-indirect.stderr

@@ -1,109 +1,109 @@
 error[E0720]: opaque type expands to a recursive type
-  --> $DIR/recursive-impl-trait-type.rs:6:22
+  --> $DIR/recursive-impl-trait-type-indirect.rs:6:22
    |
 LL | fn option(i: i32) -> impl Sized {
    |                      ^^^^^^^^^^ expands to a recursive type
    |
    = note: expanded type is `std::option::Option<(impl Sized, i32)>`
 
 error[E0720]: opaque type expands to a recursive type
-  --> $DIR/recursive-impl-trait-type.rs:14:15
+  --> $DIR/recursive-impl-trait-type-indirect.rs:14:15
    |
 LL | fn tuple() -> impl Sized {
    |               ^^^^^^^^^^ expands to a recursive type
    |
    = note: expanded type is `(impl Sized,)`
 
 error[E0720]: opaque type expands to a recursive type
-  --> $DIR/recursive-impl-trait-type.rs:18:15
+  --> $DIR/recursive-impl-trait-type-indirect.rs:18:15
    |
 LL | fn array() -> impl Sized {
    |               ^^^^^^^^^^ expands to a recursive type
    |
    = note: expanded type is `[impl Sized; 1]`
 
 error[E0720]: opaque type expands to a recursive type
-  --> $DIR/recursive-impl-trait-type.rs:22:13
+  --> $DIR/recursive-impl-trait-type-indirect.rs:22:13
    |
 LL | fn ptr() -> impl Sized {
    |             ^^^^^^^^^^ expands to a recursive type
    |
    = note: expanded type is `*const impl Sized`
 
 error[E0720]: opaque type expands to a recursive type
-  --> $DIR/recursive-impl-trait-type.rs:26:16
+  --> $DIR/recursive-impl-trait-type-indirect.rs:26:16
    |
 LL | fn fn_ptr() -> impl Sized {
    |                ^^^^^^^^^^ expands to a recursive type
    |
    = note: expanded type is `fn() -> impl Sized`
 
 error[E0720]: opaque type expands to a recursive type
-  --> $DIR/recursive-impl-trait-type.rs:30:25
+  --> $DIR/recursive-impl-trait-type-indirect.rs:30:25
    |
 LL | fn closure_capture() -> impl Sized {
    |                         ^^^^^^^^^^ expands to a recursive type
    |
-   = note: expanded type is `[closure@$DIR/recursive-impl-trait-type.rs:32:5: 32:19 x:impl Sized]`
+   = note: expanded type is `[closure@$DIR/recursive-impl-trait-type-indirect.rs:32:5: 32:19 x:impl Sized]`
 
 error[E0720]: opaque type expands to a recursive type
-  --> $DIR/recursive-impl-trait-type.rs:35:29
+  --> $DIR/recursive-impl-trait-type-indirect.rs:35:29
    |
 LL | fn closure_ref_capture() -> impl Sized {
    |                             ^^^^^^^^^^ expands to a recursive type
    |
-   = note: expanded type is `[closure@$DIR/recursive-impl-trait-type.rs:37:5: 37:20 x:impl Sized]`
+   = note: expanded type is `[closure@$DIR/recursive-impl-trait-type-indirect.rs:37:5: 37:20 x:impl Sized]`
 
 error[E0720]: opaque type expands to a recursive type
-  --> $DIR/recursive-impl-trait-type.rs:40:21
+  --> $DIR/recursive-impl-trait-type-indirect.rs:40:21
    |
 LL | fn closure_sig() -> impl Sized {
    |                     ^^^^^^^^^^ expands to a recursive type
    |
-   = note: expanded type is `[closure@$DIR/recursive-impl-trait-type.rs:41:5: 41:21]`
+   = note: expanded type is `[closure@$DIR/recursive-impl-trait-type-indirect.rs:41:5: 41:21]`
 
 error[E0720]: opaque type expands to a recursive type
-  --> $DIR/recursive-impl-trait-type.rs:44:23
+  --> $DIR/recursive-impl-trait-type-indirect.rs:44:23
    |
 LL | fn generator_sig() -> impl Sized {
    |                       ^^^^^^^^^^ expands to a recursive type
    |
-   = note: expanded type is `[closure@$DIR/recursive-impl-trait-type.rs:45:5: 45:23]`
+   = note: expanded type is `[closure@$DIR/recursive-impl-trait-type-indirect.rs:45:5: 45:23]`
 
 error[E0720]: opaque type expands to a recursive type
-  --> $DIR/recursive-impl-trait-type.rs:48:27
+  --> $DIR/recursive-impl-trait-type-indirect.rs:48:27
    |
 LL | fn generator_capture() -> impl Sized {
    |                           ^^^^^^^^^^ expands to a recursive type
    |
-   = note: expanded type is `[generator@$DIR/recursive-impl-trait-type.rs:50:5: 50:26 x:impl Sized {()}]`
+   = note: expanded type is `[generator@$DIR/recursive-impl-trait-type-indirect.rs:50:5: 50:26 x:impl Sized {()}]`
 
 error[E0720]: opaque type expands to a recursive type
-  --> $DIR/recursive-impl-trait-type.rs:53:26
+  --> $DIR/recursive-impl-trait-type-indirect.rs:53:26
    |
 LL | fn substs_change<T>() -> impl Sized {
    |                          ^^^^^^^^^^ expands to a recursive type
    |
    = note: expanded type is `(impl Sized,)`
 
 error[E0720]: opaque type expands to a recursive type
-  --> $DIR/recursive-impl-trait-type.rs:57:24
+  --> $DIR/recursive-impl-trait-type-indirect.rs:57:24
    |
 LL | fn generator_hold() -> impl Sized {
    |                        ^^^^^^^^^^ expands to a recursive type
    |
-   = note: expanded type is `[generator@$DIR/recursive-impl-trait-type.rs:58:5: 62:6 {impl Sized, ()}]`
+   = note: expanded type is `[generator@$DIR/recursive-impl-trait-type-indirect.rs:58:5: 62:6 {impl Sized, ()}]`
 
 error[E0720]: opaque type expands to a recursive type
-  --> $DIR/recursive-impl-trait-type.rs:69:26
+  --> $DIR/recursive-impl-trait-type-indirect.rs:69:26
    |
 LL | fn mutual_recursion() -> impl Sync {
    |                          ^^^^^^^^^ expands to a recursive type
    |
    = note: type resolves to itself
 
 error[E0720]: opaque type expands to a recursive type
-  --> $DIR/recursive-impl-trait-type.rs:73:28
+  --> $DIR/recursive-impl-trait-type-indirect.rs:73:28
    |
 LL | fn mutual_recursion_b() -> impl Sized {
    |                            ^^^^^^^^^^ expands to a recursive type

src/test/ui/impl-trait/recursive-impl-trait-type--through-non-recursize.stderr → src/test/ui/impl-trait/recursive-impl-trait-type-through-non-recursive.stderr

@@ -1,29 +1,29 @@
 error[E0720]: opaque type expands to a recursive type
-  --> $DIR/recursive-impl-trait-type--through-non-recursize.rs:7:22
+  --> $DIR/recursive-impl-trait-type-through-non-recursive.rs:7:22
    |
 LL | fn recursive_id() -> impl Sized {
    |                      ^^^^^^^^^^ expands to a recursive type
    |
    = note: type resolves to itself
 
 error[E0720]: opaque type expands to a recursive type
-  --> $DIR/recursive-impl-trait-type--through-non-recursize.rs:11:23
+  --> $DIR/recursive-impl-trait-type-through-non-recursive.rs:11:23
    |
 LL | fn recursive_id2() -> impl Sized {
    |                       ^^^^^^^^^^ expands to a recursive type
    |
    = note: type resolves to itself
 
 error[E0720]: opaque type expands to a recursive type
-  --> $DIR/recursive-impl-trait-type--through-non-recursize.rs:17:24
+  --> $DIR/recursive-impl-trait-type-through-non-recursive.rs:17:24
    |
 LL | fn recursive_wrap() -> impl Sized {
    |                        ^^^^^^^^^^ expands to a recursive type
    |
    = note: expanded type is `((impl Sized,),)`
 
 error[E0720]: opaque type expands to a recursive type
-  --> $DIR/recursive-impl-trait-type--through-non-recursize.rs:21:25
+  --> $DIR/recursive-impl-trait-type-through-non-recursive.rs:21:25
    |
 LL | fn recursive_wrap2() -> impl Sized {
    |                         ^^^^^^^^^^ expands to a recursive type