[SILGen] Test vtable thunk emission for overrides with contextual where clauses

Author: AnthonyLatsis

test/SILGen/vtable_thunks_reabstraction.swift

@@ -557,3 +557,32 @@ class MoreGenericSub2<TT, T> : GenericBase<T> {
 // CHECK-NEXT:   #GenericBase.init!allocator.1: <T><U> (GenericBase<T>.Type) -> (T, U) -> GenericBase<T> : @$s27vtable_thunks_reabstraction15MoreGenericSub2C1t1uACyxq_Gq__qd__tclufC [override]
 // CHECK-NEXT:   #MoreGenericSub2.deinit!deallocator.1: @$s27vtable_thunks_reabstraction15MoreGenericSub2CfD     // MoreGenericSub2.__deallocating_deinit
 // CHECK-NEXT: }
+
+protocol SE_0267_P1 {}
+
+class SE_0267_Base1<T> {
+  func foo() where T: SE_0267_P1 {}
+}
+class SE_0267_Derived1<T>: SE_0267_Base1<T> {
+  override func foo() {}
+}
+
+// CHECK-LABEL: sil_vtable SE_0267_Derived1 {
+// CHECK-NEXT:   #SE_0267_Base1.foo: <T where T : SE_0267_P1> (SE_0267_Base1<T>) -> () -> () : @$s27vtable_thunks_reabstraction16SE_0267_Derived1C3fooyyFAA0D11_0267_Base1CADyyAA0D8_0267_P1RzlFTV [override]
+// CHECK-NEXT:   #SE_0267_Base1.init
+// CHECK-NEXT:   #SE_0267_Derived1.foo: <T> (SE_0267_Derived1<T>) -> () -> () : @$s27vtable_thunks_reabstraction16SE_0267_Derived1C3fooyyF
+// CHECK-NEXT:   #SE_0267_Derived1.deinit
+// CHECK-NEXT:   }
+
+class SE_0267_Base2<T> {
+  func foo() -> T where T: FixedWidthInteger { fatalError() }
+}
+class SE_0267_Derived2: SE_0267_Base2<Int> {
+  override func foo() -> Int { return .zero }
+}
+
+// CHECK-LABEL: sil_vtable SE_0267_Derived2 {
+// CHECK-NEXT:   #SE_0267_Base2.foo: <T where T : FixedWidthInteger> (SE_0267_Base2<T>) -> () -> T : @$s27vtable_thunks_reabstraction16SE_0267_Derived2C3fooSiyFAA0D11_0267_Base2CADxys17FixedWidthIntegerRzlFTV [override]
+// CHECK-NEXT:   #SE_0267_Base2.init
+// CHECK-NEXT:   #SE_0267_Derived2.deinit
+// CHECK-NEXT:   }

test/attr/attr_override.swift

@@ -579,7 +579,7 @@ class SR_4206_DerivedGeneric_6<T>: SR_4206_BaseConcrete_6 {
   override func foo<T: SR_4206_Protocol_1>(arg: T) {} // expected-error {{overridden method 'foo' has generic signature <T, T where T : SR_4206_Protocol_1> which is incompatible with base method's generic signature <T where T : SR_4206_Protocol_2>; expected generic signature to be <T, T where T : SR_4206_Protocol_2>}}
 }
 
-// Where clauses on contextually generic declarations
+// Contextual where clauses on non-generic members
 
 class SR_4206_Base_7<T> {
   func foo1() where T: SR_4206_Protocol_1 {} // expected-note {{overridden declaration is here}}
@@ -598,6 +598,14 @@ class SR_4206_Base_8<T> {
   func foo() where T: SR_4206_Protocol_1 {}
 }
 class SR_4206_Derived_8<T: SR_4206_Protocol_2, U>: SR_4206_Base_8<T> {
+  // Because the generic signature of foo() is the same either way,
+  // it may seem confusing that placing an additional constraint on the
+  // generic parameter declaration directly has a different effect on
+  // overridability in contrast to placing the constraint on foo().
+  // The former (unlike the latter) is accepted because the constraint
+  // in question only affects the ability to initialize an instance of the
+  // subclass — not the visibility of the override itself relative to an
+  // existing instance.
   override func foo() where T: SR_4206_Protocol_1 {} // OK
 }