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:8:1
    |
 LL | type 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:8:1
+   |
+LL | type const A: u8 = A;
+   | ^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+

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

@@ -1,8 +1,12 @@
+//@ 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 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 +1,16 @@
+//@ compile-flags: -Znext-solver=globally
+#![feature(generic_const_items, min_generic_const_args)]
+#![allow(incomplete_features)]
+
+trait Owner {
+    type const C<const N: u32>: u32;
+    //~^ ERROR cycle detected when evaluating type-level constant
+}
+
+impl Owner for () {
+    type 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:6:5
+   |
+LL |     type const C<const N: u32>: u32;
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+

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

@@ -1,38 +1,18 @@
-//@ compile-flags: -Znext-solver=globally
-#![feature(generic_const_items, min_generic_const_args)]
-#![feature(adt_const_params)]
-#![allow(incomplete_features)]
-#![allow(dead_code)]
+// issue: <https://github.com/rust-lang/rust/issues/151631>
+//@ compile-flags: -Znext-solver
+#![feature(min_generic_const_args)]
+#![expect(incomplete_features)]
 
-trait Owner: NewTrait {
-    #[type_const]
-    const C<const N: u32>: u32;
-    #[type_const]
-    const K<const N: u32>: u32;
+trait SuperTrait {}
+trait Trait: SuperTrait {
+    type const K: u32;
 }
-
-trait NewTrait {}
-
-impl NewTrait for () {}
-
-impl Owner for () {
-    #[type_const]
-    const C<const N: u32>: u32 = N;
-    #[type_const]
-    const K<const N: u32>: u32 = const { 99 + 1 };
+impl Trait for () { //~ ERROR: the trait bound `(): SuperTrait` is not satisfied
+    type const K: u32 = const { 1 };
 }
 
-fn take0<const N: u32>(_: impl Owner<C<N> = { N }>) {}
-fn take1(_: impl Owner<K<99> = 100>) {}
-
-#[derive(PartialEq, Eq, std::marker::ConstParamTy)]
-enum Maybe<T> {
-    Nothing,
-    Just(T),
-}
+fn check(_: impl Trait<K = 0>) {}
 
 fn main() {
-    take0::<128>(());
-    take1(());
-    //~^ ERROR type mismatch resolving `const { 99 + 1 } == 100`
+    check(()); //~ ERROR: the trait bound `(): SuperTrait` is not satisfied
 }

tests/ui/const-generics/type-const-ice-issue-151631.rs

@@ -1,17 +1,37 @@
-error[E0271]: type mismatch resolving `const { 99 + 1 } == 100`
-  --> $DIR/type-const-ice-issue-151631.rs:36:11
+error[E0277]: the trait bound `(): SuperTrait` is not satisfied
+  --> $DIR/type-const-ice-issue-151631.rs:10:16
    |
-LL |     take1(());
-   |     ----- ^^ types differ
-   |     |
-   |     required by a bound introduced by this call
+LL | impl Trait for () {
+   |                ^^ the trait `SuperTrait` is not implemented for `()`
    |
-note: required by a bound in `take1`
-  --> $DIR/type-const-ice-issue-151631.rs:26:24
+help: this trait has no implementations, consider adding one
+  --> $DIR/type-const-ice-issue-151631.rs:6:1
    |
-LL | fn take1(_: impl Owner<K<99> = 100>) {}
-   |                        ^^^^^^^^^^^ required by this bound in `take1`
+LL | trait SuperTrait {}
+   | ^^^^^^^^^^^^^^^^
+note: required by a bound in `Trait`
+  --> $DIR/type-const-ice-issue-151631.rs:7:14
+   |
+LL | trait Trait: SuperTrait {
+   |              ^^^^^^^^^^ required by this bound in `Trait`
+
+error[E0277]: the trait bound `(): SuperTrait` is not satisfied
+  --> $DIR/type-const-ice-issue-151631.rs:17:5
+   |
+LL |     check(());
+   |     ^^^^^^^^^ the trait `SuperTrait` is not implemented for `()`
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/type-const-ice-issue-151631.rs:6:1
+   |
+LL | trait SuperTrait {}
+   | ^^^^^^^^^^^^^^^^
+note: required by a bound in `Trait`
+  --> $DIR/type-const-ice-issue-151631.rs:7:14
+   |
+LL | trait Trait: SuperTrait {
+   |              ^^^^^^^^^^ required by this bound in `Trait`
 
-error: aborting due to 1 previous error
+error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0271`.
+For more information about this error, try `rustc --explain E0277`.