[CSSimplify] Narrow down tuple wrapping for pack expansion matching

Follow-up for #82326.

The optional injection is only viable is the wrapped type is
not yet resolved, otherwise it's safe to wrap the optional.

(cherry picked from commit 4804f21)

Author: xedin

lib/Sema/CSSimplify.cpp

@@ -7354,9 +7354,15 @@ ConstraintSystem::matchTypes(Type type1, Type type2, ConstraintKind kind,
   // and `Optional<T>` which would be handled by optional injection.
   if (isTupleWithUnresolvedPackExpansion(origType1) ||
       isTupleWithUnresolvedPackExpansion(origType2)) {
+    auto isTypeVariableWrappedInOptional = [](Type type) {
+      if (type->getOptionalObjectType()) {
+        return type->lookThroughAllOptionalTypes()->isTypeVariableOrMember();
+      }
+      return false;
+    };
     if (isa<TupleType>(desugar1) != isa<TupleType>(desugar2) &&
-        !desugar1->getOptionalObjectType() &&
-        !desugar2->getOptionalObjectType() &&
+        !isTypeVariableWrappedInOptional(desugar1) &&
+        !isTypeVariableWrappedInOptional(desugar2) &&
         !desugar1->isAny() &&
         !desugar2->isAny()) {
       return matchTypes(

test/Constraints/variadic_generic_constraints.swift

@@ -77,16 +77,28 @@ func badCallToZip<each T, each U>(t: repeat each T, u: repeat each U) {
   // expected-error@-2 {{pack expansion requires that 'each U' and 'each T' have the same shape}}
 }
 
-do {
-  func test<A, B, each C>(
+func variadicGenericsInOptionalContext(v: Int?) {
+  func test1<A, B, each C>(
     _: A,
     _: B,
     _: repeat each C
   ) throws -> (A, B, repeat each C) {
     fatalError()
   }
 
+  func test2<A, B, each C>(
+    _: A,
+    _: B,
+    _: (repeat each C)
+  ) throws -> (A, B, repeat each C) {
+    fatalError()
+  }
+
   func test() {
-    guard let _ = try? test(1, 2, 3) else { return } // Ok
+    guard let _ = try? test1(1, 2, 3) else { return } // Ok
+    guard let _ = try? test1(1, 2, v) else { return } // Ok
+
+    guard let _ = try? test2(1, 2, 3) else { return } // Ok
+    guard let _ = try? test2(1, 2, v) else { return } // Ok
   }
 }