moved renamed docs formatted | defaults-well-formedness.rs

Author: Kivooeo

tests/ui/defaults-well-formedness.rs

@@ -0,0 +1,54 @@
+//! Test for well-formedness checking of default type parameters.
+//!
+//! This test verifies that the compiler correctly handles various cases
+//! where default type parameters may or may not be checked for well-formedness
+//! in where clauses.
+//!
+//! Issue: https://github.com/rust-lang/rust/issues/49344
+
+//@ run-pass
+
+#![allow(dead_code)]
+
+trait Trait<T> {}
+struct Foo<U, V = i32>(U, V)
+where
+    U: Trait<V>;
+
+trait Marker {}
+struct TwoParams<T, U>(T, U);
+impl Marker for TwoParams<i32, i32> {}
+
+// Clauses with more than 1 param are not checked.
+struct IndividuallyBogus<T = i32, U = i32>(TwoParams<T, U>)
+where
+    TwoParams<T, U>: Marker;
+
+struct BogusTogether<T = u32, U = i32>(T, U)
+where
+    TwoParams<T, U>: Marker;
+
+// Clauses with non-defaulted params are not checked.
+struct NonDefaultedInClause<T, U = i32>(TwoParams<T, U>)
+where
+    TwoParams<T, U>: Marker;
+
+struct DefaultedLhs<U, V = i32>(U, V)
+where
+    V: Trait<U>;
+
+// Dependent defaults are not checked.
+struct Dependent<T, U = T>(T, U)
+where
+    U: Copy;
+
+trait SelfBound<T: Copy = Self> {}
+
+// Not even for well-formedness.
+struct WellFormedProjection<A, T = <A as Iterator>::Item>(A, T);
+
+// Issue #49344, predicates with lifetimes should not be checked.
+trait Scope<'a> {}
+struct Request<'a, S: Scope<'a> = i32>(S, &'a ());
+
+fn main() {}