Pass the correct DefId when suggesting writing the aliased Self type out

compiler/rustc_hir_typeck/src/demand.rs

@@ -1071,7 +1071,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     err.span_suggestion_verbose(
                         *span,
                         "use the type name directly",
-                        self.tcx.value_path_str_with_args(*alias_to, e_args),
+                        self.tcx.value_path_str_with_args(e_def.did(), e_args),
                         Applicability::MaybeIncorrect,
                     );
                 }

tests/ui/typeck/ice-self-mismatch-const-generics.rs

@@ -0,0 +1,25 @@
+// Checks that the following does not ICE when constructing type mismatch diagnostic involving
+// `Self` and const generics.
+// Issue: <https://github.com/rust-lang/rust/issues/122467>
+
+pub struct GenericStruct<const N: usize, T> {
+    thing: T,
+}
+
+impl<T> GenericStruct<0, T> {
+    pub fn new(thing: T) -> GenericStruct<1, T> {
+        Self { thing }
+        //~^ ERROR mismatched types
+    }
+}
+
+pub struct GenericStruct2<const M: usize, T>(T);
+
+impl<T> GenericStruct2<0, T> {
+    pub fn new(thing: T) -> GenericStruct2<1, T> {
+        Self { 0: thing }
+        //~^ ERROR mismatched types
+    }
+}
+
+fn main() {}

tests/ui/typeck/ice-self-mismatch-const-generics.stderr

@@ -0,0 +1,37 @@
+error[E0308]: mismatched types
+  --> $DIR/ice-self-mismatch-const-generics.rs:11:9
+   |
+LL | impl<T> GenericStruct<0, T> {
+   |         ------------------- this is the type of the `Self` literal
+LL |     pub fn new(thing: T) -> GenericStruct<1, T> {
+   |                             ------------------- expected `GenericStruct<1, T>` because of return type
+LL |         Self { thing }
+   |         ^^^^^^^^^^^^^^ expected `1`, found `0`
+   |
+   = note: expected struct `GenericStruct<_, 1>`
+              found struct `GenericStruct<_, 0>`
+help: use the type name directly
+   |
+LL |         GenericStruct::<1, T> { thing }
+   |         ~~~~~~~~~~~~~~~~~~~~~
+
+error[E0308]: mismatched types
+  --> $DIR/ice-self-mismatch-const-generics.rs:20:9
+   |
+LL | impl<T> GenericStruct2<0, T> {
+   |         -------------------- this is the type of the `Self` literal
+LL |     pub fn new(thing: T) -> GenericStruct2<1, T> {
+   |                             -------------------- expected `GenericStruct2<1, T>` because of return type
+LL |         Self { 0: thing }
+   |         ^^^^^^^^^^^^^^^^^ expected `1`, found `0`
+   |
+   = note: expected struct `GenericStruct2<_, 1>`
+              found struct `GenericStruct2<_, 0>`
+help: use the type name directly
+   |
+LL |         GenericStruct2::<1, T> { 0: thing }
+   |         ~~~~~~~~~~~~~~~~~~~~~~
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0308`.