Add new UI tests

Author: LlewVallis

tests/ui/unconstrained-generic-parameters/mentioned-but-unconstrained-const-generic.rs

@@ -0,0 +1,17 @@
+trait Foo1 {}
+
+trait Foo2 {
+    type Bar;
+}
+
+impl<const N: usize> Foo1 for u32 where [u32; N]: Clone {}
+//~^ ERROR: the const parameter `N` is not constrained
+
+impl<T, const N: usize> Foo1 for String where T: Iterator<Item = [u32; N]> {}
+//~^ ERROR: the type parameter `T` is not constrained
+//~| ERROR: the const parameter `N` is not constrained
+
+impl<T, const N: usize> Foo2 for T where T: Foo2<Bar = [u32; N]> { type Bar = [u32; N]; }
+//~^ ERROR: the const parameter `N` is not constrained
+
+fn main() {}

tests/ui/unconstrained-generic-parameters/mentioned-but-unconstrained-const-generic.stderr

@@ -0,0 +1,43 @@
+error[E0207]: the const parameter `N` is not constrained by the impl trait, self type, or predicates
+  --> $DIR/mentioned-but-unconstrained-const-generic.rs:7:6
+   |
+LL | impl<const N: usize> Foo1 for u32 where [u32; N]: Clone {}
+   |      ^^^^^^^^^^^^^^ unconstrained const parameter
+   |
+   = note: to constrain `N`, use it in the implemented trait, in the self type, or in an equality with an associated type
+   = note: expressions using a const parameter must map each value to a distinct output value
+   = note: proving the result of expressions other than the parameter are unique is not supported
+
+error[E0207]: the type parameter `T` is not constrained by the impl trait, self type, or predicates
+  --> $DIR/mentioned-but-unconstrained-const-generic.rs:10:6
+   |
+LL | impl<T, const N: usize> Foo1 for String where T: Iterator<Item = [u32; N]> {}
+   |      ^ unconstrained type parameter
+   |
+   = note: to constrain `T`, use it in the implemented trait, in the self type, or in an equality with an associated type
+
+error[E0207]: the const parameter `N` is not constrained by the impl trait, self type, or predicates
+  --> $DIR/mentioned-but-unconstrained-const-generic.rs:10:9
+   |
+LL | impl<T, const N: usize> Foo1 for String where T: Iterator<Item = [u32; N]> {}
+   |         ^^^^^^^^^^^^^^ unconstrained const parameter
+   |
+   = note: to constrain `N`, use it in the implemented trait, in the self type, or in an equality with an associated type
+   = note: `N` is bound to an associated type, but the reference to the associated type itself uses unconstrained generic parameters
+   = note: expressions using a const parameter must map each value to a distinct output value
+   = note: proving the result of expressions other than the parameter are unique is not supported
+
+error[E0207]: the const parameter `N` is not constrained by the impl trait, self type, or predicates
+  --> $DIR/mentioned-but-unconstrained-const-generic.rs:14:9
+   |
+LL | impl<T, const N: usize> Foo2 for T where T: Foo2<Bar = [u32; N]> { type Bar = [u32; N]; }
+   |         ^^^^^^^^^^^^^^ unconstrained const parameter
+   |
+   = note: to constrain `N`, use it in the implemented trait, in the self type, or in an equality with an associated type
+   = note: `N` is bound to an associated type, but the associated type is circularly defined in this impl
+   = note: expressions using a const parameter must map each value to a distinct output value
+   = note: proving the result of expressions other than the parameter are unique is not supported
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0207`.

tests/ui/unconstrained-generic-parameters/mentioned-but-unconstrained-type.rs

@@ -0,0 +1,24 @@
+trait Foo1 {}
+
+trait Foo2 {
+    type Bar;
+}
+
+trait Foo3 {
+    type Bar;
+}
+
+impl<T> Foo1 for u32 where T: Clone {}
+//~^ ERROR: the type parameter `T` is not constrained
+
+impl<T, U> Foo1 for String where T: Iterator<Item = U> {}
+//~^ ERROR: the type parameter `T` is not constrained
+//~| ERROR: the type parameter `U` is not constrained
+
+impl<T, U> Foo2 for T where T: Foo2<Bar = U> { type Bar = U; }
+//~^ ERROR: the type parameter `U` is not constrained
+
+impl<T, U> Foo3 for T where T: Foo3<Bar = Option<U>> { type Bar = Option<U>; }
+//~^ ERROR: the type parameter `U` is not constrained
+
+fn main() {}

tests/ui/unconstrained-generic-parameters/mentioned-but-unconstrained-type.stderr

@@ -0,0 +1,46 @@
+error[E0207]: the type parameter `T` is not constrained by the impl trait, self type, or predicates
+  --> $DIR/mentioned-but-unconstrained-type.rs:11:6
+   |
+LL | impl<T> Foo1 for u32 where T: Clone {}
+   |      ^ unconstrained type parameter
+   |
+   = note: to constrain `T`, use it in the implemented trait, in the self type, or in an equality with an associated type
+
+error[E0207]: the type parameter `T` is not constrained by the impl trait, self type, or predicates
+  --> $DIR/mentioned-but-unconstrained-type.rs:14:6
+   |
+LL | impl<T, U> Foo1 for String where T: Iterator<Item = U> {}
+   |      ^ unconstrained type parameter
+   |
+   = note: to constrain `T`, use it in the implemented trait, in the self type, or in an equality with an associated type
+
+error[E0207]: the type parameter `U` is not constrained by the impl trait, self type, or predicates
+  --> $DIR/mentioned-but-unconstrained-type.rs:14:9
+   |
+LL | impl<T, U> Foo1 for String where T: Iterator<Item = U> {}
+   |         ^ unconstrained type parameter
+   |
+   = note: to constrain `U`, use it in the implemented trait, in the self type, or in an equality with an associated type
+   = note: `U` is bound to an associated type, but the reference to the associated type itself uses unconstrained generic parameters
+
+error[E0207]: the type parameter `U` is not constrained by the impl trait, self type, or predicates
+  --> $DIR/mentioned-but-unconstrained-type.rs:18:9
+   |
+LL | impl<T, U> Foo2 for T where T: Foo2<Bar = U> { type Bar = U; }
+   |         ^ unconstrained type parameter
+   |
+   = note: to constrain `U`, use it in the implemented trait, in the self type, or in an equality with an associated type
+   = note: `U` is bound to an associated type, but the associated type is circularly defined in this impl
+
+error[E0207]: the type parameter `U` is not constrained by the impl trait, self type, or predicates
+  --> $DIR/mentioned-but-unconstrained-type.rs:21:9
+   |
+LL | impl<T, U> Foo3 for T where T: Foo3<Bar = Option<U>> { type Bar = Option<U>; }
+   |         ^ unconstrained type parameter
+   |
+   = note: to constrain `U`, use it in the implemented trait, in the self type, or in an equality with an associated type
+   = note: `U` is bound to an associated type, but the associated type is circularly defined in this impl
+
+error: aborting due to 5 previous errors
+
+For more information about this error, try `rustc --explain E0207`.

tests/ui/unconstrained-generic-parameters/unused-const-generic.rs

@@ -0,0 +1,14 @@
+struct Foo;
+
+impl<const N: usize> Foo {}
+//~^ ERROR: the const parameter `N` is not constrained
+
+impl<const N: usize> Default for Foo {
+    //~^ ERROR: the const parameter `N` is not constrained
+    fn default() -> Self { Foo }
+}
+
+// This one isn't an error
+fn foo<const N: usize>() {}
+
+fn main() {}

tests/ui/unconstrained-generic-parameters/unused-const-generic.stderr

@@ -0,0 +1,23 @@
+error[E0207]: the const parameter `N` is not constrained by the impl trait, self type, or predicates
+  --> $DIR/unused-const-generic.rs:3:6
+   |
+LL | impl<const N: usize> Foo {}
+   |      ^^^^^^^^^^^^^^ unconstrained const parameter
+   |
+   = note: to constrain `N`, use it in the self type, or in an equality with an associated type
+   = note: expressions using a const parameter must map each value to a distinct output value
+   = note: proving the result of expressions other than the parameter are unique is not supported
+
+error[E0207]: the const parameter `N` is not constrained by the impl trait, self type, or predicates
+  --> $DIR/unused-const-generic.rs:6:6
+   |
+LL | impl<const N: usize> Default for Foo {
+   |      ^^^^^^^^^^^^^^ unconstrained const parameter
+   |
+   = note: to constrain `N`, use it in the implemented trait, in the self type, or in an equality with an associated type
+   = note: expressions using a const parameter must map each value to a distinct output value
+   = note: proving the result of expressions other than the parameter are unique is not supported
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0207`.

tests/ui/unconstrained-generic-parameters/unused-type-generic.rs

@@ -0,0 +1,14 @@
+struct Foo;
+
+impl<T> Foo {}
+//~^ ERROR: the type parameter `T` is not constrained
+
+impl<T> Default for Foo {
+    //~^ ERROR: the type parameter `T` is not constrained
+    fn default() -> Self { Foo }
+}
+
+// This one isn't an error
+fn foo<T>() {}
+
+fn main() {}

tests/ui/unconstrained-generic-parameters/unused-type-generic.stderr

@@ -0,0 +1,19 @@
+error[E0207]: the type parameter `T` is not constrained by the impl trait, self type, or predicates
+  --> $DIR/unused-type-generic.rs:3:6
+   |
+LL | impl<T> Foo {}
+   |      ^ unconstrained type parameter
+   |
+   = note: to constrain `T`, use it in the self type, or in an equality with an associated type
+
+error[E0207]: the type parameter `T` is not constrained by the impl trait, self type, or predicates
+  --> $DIR/unused-type-generic.rs:6:6
+   |
+LL | impl<T> Default for Foo {
+   |      ^ unconstrained type parameter
+   |
+   = note: to constrain `T`, use it in the implemented trait, in the self type, or in an equality with an associated type
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0207`.