Merge pull request swiftlang#85864 from slavapestov/fix-rdar165909327-6.3

Sema: Re-visit @Specialize attribute where clause in interface resolution stage [6.3]

Author: slavapestov

lib/Sema/TypeCheckAttr.cpp

@@ -3590,6 +3590,12 @@ void AttributeChecker::visitAbstractSpecializeAttr(AbstractSpecializeAttr *attr)
   }
 
   (void)attr->getSpecializedSignature(FD);
+
+  // Force resolution of interface types written in requirements here to check
+  // that generic types satisfy generic requirements, and so on.
+  WhereClauseOwner(FD, attr)
+      .visitRequirements(TypeResolutionStage::Interface,
+                         [](Requirement, RequirementRepr *) { return false; });
 }
 
 GenericSignature

lib/Sema/TypeCheckDeclPrimary.cpp

@@ -602,7 +602,8 @@ static void checkGenericParams(GenericContext *ownerCtx) {
     checkInheritanceClause(gp);
   }
 
-  // Force resolution of interface types written in requirements here.
+  // Force resolution of interface types written in requirements here to check
+  // that generic types satisfy generic requirements, and so on.
   WhereClauseOwner(ownerCtx)
       .visitRequirements(TypeResolutionStage::Interface,
                          [](Requirement, RequirementRepr *) { return false; });

test/attr/attr_specialize.swift

@@ -405,3 +405,9 @@ func nonGenericParam2(x: Int) {}
 @_specialize(where T == Int)
 @_specialize(where T == Int)
 func genericParamDuplicate<T>(t: T) {}
+
+struct GG<T: P> {}
+
+// expected-error@+1 {{type 'String' does not conform to protocol 'P'}}
+@_specialize(where T == GG<String>)
+func genericArgInvalidSpecialize<T>(t: T) {}