Sema: Handle SameShape requirements in doesMemberHaveUnfulfillableConstraintsWithExistentialBase()

Author: slavapestov

lib/Sema/ConstraintSystem.cpp

@@ -7479,9 +7479,6 @@ static bool doesMemberHaveUnfulfillableConstraintsWithExistentialBase(
 
   for (const auto &req : sig.getRequirements()) {
     switch (req.getKind()) {
-    case RequirementKind::SameShape:
-      llvm_unreachable("Same-shape requirement not supported here");
-
     case RequirementKind::Superclass: {
       if (req.getFirstType()->getRootGenericParam()->getDepth() > 0 &&
           req.getSecondType().walk(isDependentOnSelfWalker)) {
@@ -7490,7 +7487,8 @@ static bool doesMemberHaveUnfulfillableConstraintsWithExistentialBase(
 
       break;
     }
-    case RequirementKind::SameType: {
+    case RequirementKind::SameType:
+    case RequirementKind::SameShape: {
       const auto isNonSelfRootedTypeParam = [](Type ty) {
         return ty->isTypeParameter() &&
                ty->getRootGenericParam()->getDepth() > 0;

test/decl/protocol/existential_member_accesses_self_assoctype.swift

@@ -1024,3 +1024,12 @@ do {
   let _: Array<any Class2Base & CovariantAssocTypeErasureDerived> = exist.method11()
   let _: Dictionary<String, any Class2Base & CovariantAssocTypeErasureDerived> = exist.method12()
 }
+
+// Same-shape requirements
+protocol HasSameShape {
+  func foo<each T, each U>(t: repeat each T, u: repeat each U) -> (repeat (each T, each U))
+}
+
+func bar(a: any HasSameShape) -> (Int, String) {
+  a.foo(t: 1, u: "hi")
+}