guard recursive type-const evaluation

Author: JohnTitor

compiler/rustc_trait_selection/src/traits/mod.rs

@@ -1,5 +1,5 @@
 error[E0275]: overflow normalizing the unevaluated constant `A`
-  --> $DIR/type_const-recursive.rs:5:1
+  --> $DIR/type_const-recursive.rs:9:1
    |
 LL | const A: u8 = A;
    | ^^^^^^^^^^^

…enerics/mgca/type_const-recursive.stderr …mgca/type_const-recursive.current.stderrtests/ui/const-generics/mgca/type_const-recursive.stderr renamed to tests/ui/const-generics/mgca/type_const-recursive.current.stderr tests/ui/const-generics/mgca/type_const-recursive.stderr renamed to tests/ui/const-generics/mgca/type_const-recursive.current.stderr

@@ -0,0 +1,8 @@
+error: cycle detected when evaluating type-level constant
+  --> $DIR/type_const-recursive.rs:9:1
+   |
+LL | const A: u8 = A;
+   | ^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+

tests/ui/const-generics/mgca/type_const-recursive.next.stderr

@@ -1,8 +1,13 @@
+//@ revisions: current next
+//@[next] compile-flags: -Znext-solver
+//@ ignore-compare-mode-next-solver (explicit revisions)
+
 #![expect(incomplete_features)]
 #![feature(min_generic_const_args)]
 
 #[type_const]
 const A: u8 = A;
-//~^ ERROR: overflow normalizing the unevaluated constant `A` [E0275]
+//[current]~^ ERROR: overflow normalizing the unevaluated constant `A` [E0275]
+//[next]~^^ ERROR cycle detected when evaluating type-level constant
 
 fn main() {}

tests/ui/const-generics/mgca/type_const-recursive.rs

@@ -0,0 +1,18 @@
+//@ compile-flags: -Znext-solver=globally
+#![feature(generic_const_items, min_generic_const_args)]
+#![allow(incomplete_features)]
+
+trait Owner {
+    #[type_const]
+    const C<const N: u32>: u32;
+    //~^ ERROR cycle detected when evaluating type-level constant
+}
+
+impl Owner for () {
+    #[type_const]
+    const C<const N: u32>: u32 = { <() as Owner>::C::<N> };
+}
+
+type Arr = [u8; <() as Owner>::C::<0>];
+
+fn main() {}

tests/ui/const-generics/type-const-cycle.rs

@@ -0,0 +1,8 @@
+error: cycle detected when evaluating type-level constant
+  --> $DIR/type-const-cycle.rs:7:5
+   |
+LL |     const C<const N: u32>: u32;
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+