Merge pull request #62392 from xedin/issue-62390

[CSSimplify] Account for tuple splat when resolving closure parameters

Author: xedin

lib/Sema/CSSimplify.cpp

@@ -10595,6 +10595,27 @@ bool ConstraintSystem::resolveClosure(TypeVariableType *typeVar,
       return None;
 
     auto numContextualParams = fnType->getNumParams();
+
+    if (numContextualParams == 1) {
+      const auto &param = fnType->getParams()[0];
+      if (auto *tuple = param.getPlainType()->getAs<TupleType>()) {
+        // If arity is the same it's a tuple splat which is allowed
+        // for closures (see SE-0110 for more details):
+        //
+        // func test(_: ((Int, Int)) -> Void) {}
+        // test { (arg, _) in
+        //   ...
+        // }
+        if (tuple->getNumElements() == inferredClosureType->getNumParams() &&
+            param.getParameterFlags().isNone()) {
+          const auto &elt = tuple->getElement(index);
+          return AnyFunctionType::Param(elt.getType(), elt.getName());
+        }
+
+        return None;
+      }
+    }
+
     if (numContextualParams != inferredClosureType->getNumParams() ||
         numContextualParams <= index)
       return None;

test/Constraints/closures.swift

@@ -386,7 +386,7 @@ func rdar21078316() {
 
 // <rdar://problem/20978044> QoI: Poor diagnostic when using an incorrect tuple element in a closure
 var numbers = [1, 2, 3]
-zip(numbers, numbers).filter { $0.2 > 1 }  // expected-error {{value of tuple type '(Array<Int>.Element, Array<Int>.Element)' has no member '2'}}
+zip(numbers, numbers).filter { $0.2 > 1 }  // expected-error {{value of tuple type '(Int, Int)' has no member '2'}}
 
 
 

validation-test/Sema/type_checker_perf/fast/issue-62390.swift

@@ -0,0 +1,11 @@
+// RUN: %target-typecheck-verify-swift -solver-expression-time-threshold=1
+// REQUIRES: tools-release,no_asan
+
+// https://github.com/apple/swift/issues/62390
+// Compiler is extremely slow to compile simple closure
+
+func testFn<U>(_: ((Int, Int)) -> U) {}
+
+testFn { (a, _) in
+  return ((a <= a && a >= a) || (a <= a && a >= a)) // Ok
+}