Add regression test

As well as matching error outputs

Author: JulianKnodt

src/test/ui/const-generics/issues/issue-72787.rs

@@ -0,0 +1,32 @@
+#![feature(const_generics)]
+#![allow(incomplete_features)]
+
+pub struct IsLessOrEqual<const LHS: u32, const RHS: u32>;
+pub struct Condition<const CONDITION: bool>;
+pub trait True {}
+
+impl<const LHS: u32, const RHS: u32> True for IsLessOrEqual<LHS, RHS> where
+    Condition<{ LHS <= RHS }>: True
+//~^ Error constant expression depends on a generic parameter
+{
+}
+impl True for Condition<true> {}
+
+struct S<const I: u32, const J: u32>;
+impl<const I: u32, const J: u32> S<I, J>
+where
+    IsLessOrEqual<I, 8>: True,
+    IsLessOrEqual<J, 8>: True,
+    IsLessOrEqual<{ 8 - I }, { 8 - J }>: True,
+//~^ Error constant expression depends on a generic parameter
+//~| Error constant expression depends on a generic parameter
+//~| Error constant expression depends on a generic parameter
+//~| Error constant expression depends on a generic parameter
+    // Condition<{ 8 - I <= 8 - J }>: True,
+{
+    fn print() {
+        println!("I {} J {}", I, J);
+    }
+}
+
+fn main() {}

src/test/ui/const-generics/issues/issue-72787.stderr

@@ -0,0 +1,42 @@
+error: constant expression depends on a generic parameter
+  --> $DIR/issue-72787.rs:9:32
+   |
+LL |     Condition<{ LHS <= RHS }>: True
+   |                                ^^^^
+   |
+   = note: this may fail depending on what value the parameter takes
+
+error: constant expression depends on a generic parameter
+  --> $DIR/issue-72787.rs:20:42
+   |
+LL |     IsLessOrEqual<{ 8 - I }, { 8 - J }>: True,
+   |                                          ^^^^
+   |
+   = note: this may fail depending on what value the parameter takes
+
+error: constant expression depends on a generic parameter
+  --> $DIR/issue-72787.rs:20:42
+   |
+LL |     IsLessOrEqual<{ 8 - I }, { 8 - J }>: True,
+   |                                          ^^^^
+   |
+   = note: this may fail depending on what value the parameter takes
+
+error: constant expression depends on a generic parameter
+  --> $DIR/issue-72787.rs:20:42
+   |
+LL |     IsLessOrEqual<{ 8 - I }, { 8 - J }>: True,
+   |                                          ^^^^
+   |
+   = note: this may fail depending on what value the parameter takes
+
+error: constant expression depends on a generic parameter
+  --> $DIR/issue-72787.rs:20:42
+   |
+LL |     IsLessOrEqual<{ 8 - I }, { 8 - J }>: True,
+   |                                          ^^^^
+   |
+   = note: this may fail depending on what value the parameter takes
+
+error: aborting due to 5 previous errors
+