Merge pull request #30067 from xedin/rdar-59741308

[ConstraintSystem] Don't attempt bindings for closure parameters/resu…

Author: xedin

lib/Sema/CSBindings.cpp

@@ -314,6 +314,20 @@ ConstraintSystem::getPotentialBindingForRelationalConstraint(
     type = first;
     kind = AllowedBindingKind::Supertypes;
   } else {
+    // If the left-hand side of a relational constraint is a
+    // type variable representing a closure type, let's delay
+    // attempting any bindings related to any type variables
+    // on the other side since it could only be either a closure
+    // parameter or a result type, and we can't get a full set
+    // of bindings for them until closure's body is opened.
+    if (auto *typeVar = first->getAs<TypeVariableType>()) {
+      if (typeVar->getImpl().isClosureType()) {
+        result.InvolvesTypeVariables = true;
+        result.FullyBound = true;
+        return None;
+      }
+    }
+
     // Can't infer anything.
     if (result.InvolvesTypeVariables)
       return None;

test/Constraints/closures.swift

@@ -973,3 +973,22 @@ func test_correct_inference_of_closure_result_in_presence_of_optionals() {
     return;
   }
 }
+
+// rdar://problem/59741308 - inference fails with tuple element has to joined to supertype
+func rdar_59741308() {
+  class Base {
+    func foo(_: Int) {}
+  }
+
+  class A : Base {}
+  class B : Base {}
+
+  func test() {
+    // Note that `0`, and `1` here are going to be type variables
+    // which makes join impossible until it's already to late for
+    // it to be useful.
+    [(A(), 0), (B(), 1)].forEach { base, value in
+      base.foo(value) // Ok
+    }
+  }
+}

test/Constraints/function_builder_one_way.swift

@@ -49,16 +49,16 @@ func tuplify<C: Collection, T>(_ collection: C, @TupleBuilder body: (C.Element)
 }
 
 // CHECK: ---Connected components---
-// CHECK-NEXT:  0: $T1 $T2 $T3 $T5 $T6 $T7 $T8 $T10 $T11 $T78 $T79 depends on 2
-// CHECK-NEXT:  2: $T13 $T18 $T29 $T43 $T54 $T55 $T56 $T57 $T58 $T59 $T60 $T61 $T62 $T63 $T64 $T65 $T66 $T67 $T69 $T70 $T71 $T72 $T73 $T74 $T75 $T76 $T77 depends on 1, 3, 4, 6, 9
-// CHECK-NEXT:  9: $T49 $T50 $T51 $T52 $T53 depends on 8
-// CHECK-NEXT:  8: $T44 $T45 $T46 $T47 $T48
-// CHECK-NEXT:  6: $T32 $T36 $T37 $T38 $T39 $T40 $T41 $T42 depends on 5, 7
-// CHECK-NEXT:  7: $T33 $T34 $T35
-// CHECK-NEXT:  5: $T31
-// CHECK-NEXT:  4: $T19 $T20 $T21 $T22 $T23 $T24 $T25 $T26 $T27 $T28
-// CHECK-NEXT:  3: $T16 $T17
-// CHECK-NEXT:  1: $T12
+// CHECK-NEXT: 0: $T1 $T2 $T3 $T5 $T6 $T7 $T8 $T10 $T77 $T78 depends on 2
+// CHECK-NEXT: 2: $T12 $T17 $T28 $T42 $T53 $T54 $T55 $T56 $T57 $T58 $T59 $T60 $T61 $T62 $T63 $T64 $T65 $T66 $T68 $T69 $T70 $T71 $T72 $T73 $T74 $T75 $T76 depends on 1, 3, 4, 6, 9
+// CHECK-NEXT: 9: $T48 $T49 $T50 $T51 $T52 depends on 8
+// CHECK-NEXT: 8: $T43 $T44 $T45 $T46 $T47
+// CHECK-NEXT: 6: $T31 $T35 $T36 $T37 $T38 $T39 $T40 $T41 depends on 5, 7
+// CHECK-NEXT: 7: $T32 $T33 $T34
+// CHECK-NEXT: 5: $T30
+// CHECK-NEXT: 4: $T18 $T19 $T20 $T21 $T22 $T23 $T24 $T25 $T26 $T27
+// CHECK-NEXT: 3: $T15 $T16
+// CHECK-NEXT: 1: $T11
 let names = ["Alice", "Bob", "Charlie"]
 let b = true
 var number = 17