Roll back a portion of SE-0110

lib/Sema/CSSimplify.cpp

@@ -1042,11 +1042,28 @@ ConstraintSystem::matchFunctionTypes(FunctionType *func1, FunctionType *func2,
 
   increaseScore(ScoreKind::SK_FunctionConversion);
 
+  // Add a very narrow exception to SE-0110 by allowing functions that
+  // take multiple arguments to be passed as an argument in places
+  // that expect a function that takes a single tuple (of the same
+  // arity).
+  auto func1Input = func1->getInput();
+  auto func2Input = func2->getInput();
+  if (!getASTContext().isSwiftVersion3()) {
+    if (auto elt = locator.last()) {
+      if (elt->getKind() == ConstraintLocator::ApplyArgToParam) {
+        if (auto *paren2 = dyn_cast<ParenType>(func2Input.getPointer())) {
+          func2Input = paren2->getUnderlyingType();
+          if (auto *paren1 = dyn_cast<ParenType>(func1Input.getPointer()))
+            func1Input = paren1->getUnderlyingType();
+        }
+      }
+    }
+  }
+
   // Input types can be contravariant (or equal).
-  SolutionKind result = matchTypes(func2->getInput(), func1->getInput(),
-                                   subKind, subflags,
-                                   locator.withPathElement(
-                                     ConstraintLocator::FunctionArgument));
+  SolutionKind result =
+      matchTypes(func2Input, func1Input, subKind, subflags,
+                 locator.withPathElement(ConstraintLocator::FunctionArgument));
   if (result == SolutionKind::Error)
     return SolutionKind::Error;
 

test/Constraints/diagnostics_swift4.swift

@@ -39,9 +39,13 @@ func foo() -> R31898542<()> {
 
 // rdar://problem/31973368 - Cannot convert value of type '(K, V) -> ()' to expected argument type '((key: _, value: _)) -> Void'
 
+// SE-0110: We reverted to allowing this for the time being, but this
+// test is valuable in case we end up disallowing it again in the
+// future.
+
 class R<K: Hashable, V> {
   func forEach(_ body: (K, V) -> ()) {
-    var dict: [K:V] = [:]
-    dict.forEach(body) // expected-error {{nested tuple parameter '(key: K, value: V)' of function '(((key: K, value: V)) throws -> Void) throws -> ()' does not support destructuring}}
+    let dict: [K:V] = [:]
+    dict.forEach(body)
   }
 }

test/Constraints/enum_cases.swift

@@ -41,7 +41,10 @@ func bar_3<T, U>(_: (T) -> G_E<U>) {}
 
 bar_1(E.foo) // Ok
 bar_1(E.bar) // Ok
-bar_1(E.two) // expected-error {{cannot convert value of type '(Int, Int) -> E' to expected argument type '(_) -> E'}}
+// SE-0110: We reverted to allowing this for the time being, but this
+// test is valuable in case we end up disallowing it again in the
+// future.
+bar_1(E.two) // Ok since we backed off on this aspect of SE-0110 for the moment.
 bar_1(E.tuple) // Ok - it's going to be ((x: Int, y: Int))
 
 bar_2(G_E<String>.foo) // Ok

test/Constraints/tuple_arguments.swift

@@ -1338,17 +1338,17 @@ do {
   s.takesClosureTuple({ _ = $0 })
   s.takesClosureTuple({ x in })
   s.takesClosureTuple({ (x: (Double, Double)) in })
-  s.takesClosureTuple({ _ = $0; _ = $1 }) // expected-error {{closure tuple parameter '(Double, Double)' does not support destructuring with implicit parameters}}
-  s.takesClosureTuple({ (x, y) in }) // expected-error {{closure tuple parameter '(Double, Double)' does not support destructuring}} {{25-31=(arg)}} {{34-34=let (x, y) = arg; }}
-  s.takesClosureTuple({ (x: Double, y:Double) in }) // expected-error {{closure tuple parameter '(Double, Double)' does not support destructuring}} {{25-46=(arg: (Double, Double))}} {{49-49=let (x, y) = arg; }}
+  s.takesClosureTuple({ _ = $0; _ = $1 })
+  s.takesClosureTuple({ (x, y) in })
+  s.takesClosureTuple({ (x: Double, y:Double) in })
 
   let sTwo = GenericConforms<(Double, Double)>()
   sTwo.takesClosure({ _ = $0 })
   sTwo.takesClosure({ x in })
   sTwo.takesClosure({ (x: (Double, Double)) in })
-  sTwo.takesClosure({ _ = $0; _ = $1 }) // expected-error {{closure tuple parameter '(Double, Double)' does not support destructuring with implicit parameters}}
-  sTwo.takesClosure({ (x, y) in }) // expected-error {{closure tuple parameter '(Double, Double)' does not support destructuring}} {{23-29=(arg)}} {{32-32=let (x, y) = arg; }}
-  sTwo.takesClosure({ (x: Double, y: Double) in }) // expected-error {{closure tuple parameter '(Double, Double)' does not support destructuring}} {{23-45=(arg: (Double, Double))}} {{48-48=let (x, y) = arg; }}
+  sTwo.takesClosure({ _ = $0; _ = $1 })
+  sTwo.takesClosure({ (x, y) in })
+  sTwo.takesClosure({ (x: Double, y: Double) in })
 }
 
 do {
@@ -1461,7 +1461,6 @@ let pages3: MutableProperty<(data: DataSourcePage<Int>, totalCount: Int)> = Muta
 // SR-4745
 let sr4745 = [1, 2]
 let _ = sr4745.enumerated().map { (count, element) in "\(count): \(element)" }
-// expected-error@-1 {{closure tuple parameter '(offset: Int, element: Int)' does not support destructuring}} {{35-51=(arg) -> <#Result#>}} {{55-55=let (count, element) = arg; return }}
 
 // SR-4738
 
@@ -1472,7 +1471,6 @@ let sr4738 = (1, (2, 3))
 // rdar://problem/31892961
 let r31892961_1 = [1: 1, 2: 2]
 r31892961_1.forEach { (k, v) in print(k + v) }
-// expected-error@-1 {{closure tuple parameter '(key: Int, value: Int)' does not support destructuring}} {{23-29=(arg)}} {{33-33=let (k, v) = arg; }}
 
 let r31892961_2 = [1, 2, 3]
 let _: [Int] = r31892961_2.enumerated().map { ((index, val)) in
@@ -1482,15 +1480,12 @@ let _: [Int] = r31892961_2.enumerated().map { ((index, val)) in
 }
 
 let r31892961_3 = (x: 1, y: 42)
-[r31892961_3].map { (x: Int, y: Int) in x + y }
-// expected-error@-1 {{closure tuple parameter '(x: Int, y: Int)' does not support destructuring}} {{21-37=(arg: (x: Int, y: Int)) -> <#Result#>}} {{41-41=let (x, y) = arg; return }}
+_ = [r31892961_3].map { (x: Int, y: Int) in x + y }
 
-[r31892961_3].map { (x, y: Int) in x + y }
-// expected-error@-1 {{closure tuple parameter '(x: Int, y: Int)' does not support destructuring}} {{21-32=(arg: (x: Int, y: Int)) -> <#Result#>}} {{36-36=let (x, y) = arg; return }}
+_ = [r31892961_3].map { (x, y: Int) in x + y }
 
 let r31892961_4 = (1, 2)
-[r31892961_4].map { x, y in x + y }
-// expected-error@-1 {{closure tuple parameter '(Int, Int)' does not support destructuring}} {{21-25=(arg) -> <#Result#>}} {{29-29=let (x, y) = arg; return }}
+_ = [r31892961_4].map { x, y in x + y }
 
 let r31892961_5 = (x: 1, (y: 2, (w: 3, z: 4)))
 [r31892961_5].map { (x: Int, (y: Int, (w: Int, z: Int))) in x + y }
@@ -1526,3 +1521,24 @@ rdar32301091_2 { _ in }
 // expected-error@-1 {{contextual closure type '(Int, Int) -> ()' expects 2 arguments, but 1 was used in closure body}} {{19-19=,_ }}
 rdar32301091_2 { x in }
 // expected-error@-1 {{contextual closure type '(Int, Int) -> ()' expects 2 arguments, but 1 was used in closure body}} {{19-19=,<#arg#> }}
+
+func rdar32875953() {
+  let myDictionary = ["hi":1]
+
+  myDictionary.forEach {
+    print("\($0) -> \($1)")
+  }
+
+  myDictionary.forEach { key, value in
+    print("\(key) -> \(value)")
+  }
+
+  myDictionary.forEach { (key, value) in
+    print("\(key) -> \(value)")
+  }
+
+  let array1 = [1]
+  let array2 = [2]
+
+  _ = zip(array1, array2).map(+)
+}

test/Migrator/Inputs/never_compiles_safely_exits_breaking_code.swift

@@ -1 +1 @@
-func foo(_ f: (Void) -> ()) {}
+func foo(_ f: (Int) -> ()) {}