Merge pull request #64531 from xedin/pack-expansion-and-closure-params

[CSSimplify] Don't propagate contextual parameter type if it's a pack…

Author: xedin

lib/Sema/CSSimplify.cpp

@@ -11020,6 +11020,11 @@ bool ConstraintSystem::resolveClosure(TypeVariableType *typeVar,
     if (contextualTy->isTypeVariableOrMember())
       return false;
 
+    // Cannot propagate pack expansion type from context,
+    // it has to be handled by type matching logic.
+    if (contextualTy->is<PackExpansionType>())
+      return false;
+
     // If contextual type has an error, let's wait for inference,
     // otherwise contextual would interfere with diagnostics.
     if (contextualTy->hasError())

test/Constraints/pack-expansion-expressions.swift

@@ -261,3 +261,13 @@ func invalidRepeat<each T>(t: repeat each T) {
   _ = [repeat each t]
   // expected-error@-1 {{value pack expansion can only appear inside a function argument list or tuple element}}
 }
+
+func test_pack_expansions_with_closures() {
+  func takesVariadicFunction<each T>(function: (repeat each T) -> Int) {}
+
+  func test(fn: (Int, String) -> Int, x: Int) {
+    takesVariadicFunction { fn(x, "") } // Ok
+    takesVariadicFunction { y in fn(x, y) } // Ok
+    takesVariadicFunction { y, z in fn(y, z) } // Ok
+  }
+}