Sema: Allow collection downcast in cast pattern and remove the diagnostic that it is not implemented

include/swift/AST/DiagnosticsSema.def

@@ -4467,10 +4467,6 @@ NOTE(unowned_assignment_requires_strong,none,
      "a strong reference is required to prevent the instance from being "
      "deallocated", ())
 
-ERROR(isa_collection_downcast_pattern_value_unimplemented,none,
-      "collection downcast in cast pattern is not implemented; use an explicit "
-      "downcast to %0 instead", (Type))
-
 //------------------------------------------------------------------------------
 // MARK: Error-handling diagnostics
 //------------------------------------------------------------------------------

lib/Sema/TypeCheckPattern.cpp

@@ -1385,16 +1385,7 @@ Pattern *TypeChecker::coercePatternToType(ContextualPattern pattern,
     // Valid checks.
     case CheckedCastKind::ArrayDowncast:
     case CheckedCastKind::DictionaryDowncast:
-    case CheckedCastKind::SetDowncast: {
-      diags.diagnose(IP->getLoc(),
-                     diag::isa_collection_downcast_pattern_value_unimplemented,
-                     IP->getCastType());
-      IP->setType(ErrorType::get(Context));
-      if (Pattern *sub = IP->getSubPattern())
-        sub->forEachVariable([](VarDecl *VD) { VD->setInvalid(); });
-      return P;
-    }
-
+    case CheckedCastKind::SetDowncast:
     case CheckedCastKind::ValueCast:
       IP->setCastKind(castKind);
       break;

test/Parse/matching_patterns.swift

@@ -289,22 +289,57 @@ case (let (_, _, _)) + 1:
   ()
 }
 
-// FIXME: We don't currently allow subpatterns for "isa" patterns that
-// require interesting conditional downcasts.
-class Base { }
-class Derived : Base { }
+// "isa" patterns.
 
+// https://github.com/apple/swift/issues/56139
+// Allow subpatterns for "isa" patterns that require conditional
+// collection downcasts
+do {
+  class Base { }
+  class Derived : Base { }
 
-switch [Derived(), Derived(), Base()] {
-case let ds as [Derived]: // expected-error{{collection downcast in cast pattern is not implemented; use an explicit downcast to '[Derived]' instead}}
-  ()
-case is [Derived]: // expected-error{{collection downcast in cast pattern is not implemented; use an explicit downcast to '[Derived]' instead}}
-  ()
+  let arr: [Base]
 
-default:
-  ()
-}
+  if case let _ as [Derived] = arr {}
+  // expected-warning@-1 {{'let' pattern has no effect; sub-pattern didn't bind any variables}}
+  guard case let _ as [Derived] = arr else {}
+  // expected-warning@-1 {{'let' pattern has no effect; sub-pattern didn't bind any variables}}
+  while case let _ as [Derived] = arr {}
+  // expected-warning@-1 {{'let' pattern has no effect; sub-pattern didn't bind any variables}}
+
+  // FIXME: https://github.com/apple/swift/issues/61850
+  // expected-warning@+1 {{heterogeneous collection literal could only be inferred to '[[Base]]'; add explicit type annotation if this is intentional}}
+  for case _ as [Derived] in [arr] {}
+
+  if case is [Derived] = arr {}
+
+  guard case is [Derived] = arr else {}
+
+  while case is [Derived] = arr {}
+
+  for case is [Derived] in [arr] {}
+
+  switch arr {
+  case let ds as [Derived]:
+    // expected-warning@-1 {{immutable value 'ds' was never used; consider replacing with '_' or removing it}}
+    ()
+  case is [Derived]:
+    ()
+
+  default:
+    ()
+  }
 
+  let _ = { (arr: [Base]) -> Void in
+    switch arr {
+    case let ds as [Derived]:
+      // expected-warning@-1 {{immutable value 'ds' was never used; consider replacing with '_' or removing it}}
+      ()
+    default:
+      ()
+    }
+  }
+}
 
 // Optional patterns.
 let op1 : Int?

test/SILGen/statements.swift

@@ -655,6 +655,103 @@ func test_as_pattern(_ y : BaseClass) -> DerivedClass {
   // CHECK-NEXT: return [[RESULT]] : $DerivedClass
   return result
 }
+
+// https://github.com/apple/swift/issues/56139
+
+// CHECK-LABEL: sil hidden [ossa] @$s10statements31test_isa_pattern_array_downcastyySayAA9BaseClassCGF : $@convention(thin) (@guaranteed Array<BaseClass>) -> () {
+func test_isa_pattern_array_downcast(_ arr: [BaseClass]) {
+  // CHECK: [[ARR_CAST_FN:%[0-9]+]] = function_ref @$[[FN_REF:ss21_arrayConditionalCastySayq_GSgSayxGr0_lF]] : $@convention(thin) <τ_0_0, τ_0_1> (@guaranteed Array<τ_0_0>) -> @owned Optional<Array<τ_0_1>>
+  // CHECK-NEXT: [[RESULT:%[0-9]+]] = apply [[ARR_CAST_FN]]<BaseClass, DerivedClass>
+  // CHECK-NEXT: switch_enum [[RESULT]]
+  if case _ as [DerivedClass] = arr {}
+  // CHECK: [[ARR_CAST_FN:%[0-9]+]] = function_ref @$[[FN_REF]]
+  // CHECK-NEXT: [[RESULT:%[0-9]+]] = apply [[ARR_CAST_FN]]<BaseClass, DerivedClass>
+  // CHECK-NEXT: switch_enum [[RESULT]]
+  guard case _ as [DerivedClass] = arr else {}
+  // CHECK: [[ARR_CAST_FN:%[0-9]+]] = function_ref @$[[FN_REF]]
+  // CHECK-NEXT: [[RESULT:%[0-9]+]] = apply [[ARR_CAST_FN]]<BaseClass, DerivedClass>
+  // CHECK-NEXT: switch_enum [[RESULT]]
+  while case _ as [DerivedClass] = arr {}
+
+  // CHECK: [[ARR_CAST_FN:%[0-9]+]] = function_ref @$[[FN_REF]]
+  // CHECK-NEXT: [[RESULT:%[0-9]+]] = apply [[ARR_CAST_FN]]<BaseClass, DerivedClass>
+  // CHECK-NEXT: switch_enum [[RESULT]]
+  if case is [DerivedClass] = arr {}
+  // CHECK: [[ARR_CAST_FN:%[0-9]+]] = function_ref @$[[FN_REF]]
+  // CHECK-NEXT: [[RESULT:%[0-9]+]] = apply [[ARR_CAST_FN]]<BaseClass, DerivedClass>
+  // CHECK-NEXT: switch_enum [[RESULT]]
+  guard case is [DerivedClass] = arr else {}
+  // CHECK: [[ARR_CAST_FN:%[0-9]+]] = function_ref @$[[FN_REF]]
+  // CHECK-NEXT: [[RESULT:%[0-9]+]] = apply [[ARR_CAST_FN]]<BaseClass, DerivedClass>
+  // CHECK-NEXT: switch_enum [[RESULT]]
+  while case is [DerivedClass] = arr {}
+}
+// CHECK: } // end sil function '$s10statements31test_isa_pattern_array_downcastyySayAA9BaseClassCGF'
+
+// CHECK-LABEL: sil hidden [ossa] @$s10statements36test_isa_pattern_dictionary_downcastyySDySSAA9BaseClassCGF : $@convention(thin) (@guaranteed Dictionary<String, BaseClass>) -> () {
+func test_isa_pattern_dictionary_downcast(_ dict: Dictionary<String, BaseClass>) {
+  // CHECK: [[DICT_CAST_FN:%[0-9]+]] = function_ref @$[[FN_REF:ss30_dictionaryDownCastConditionalySDyq0_q1_GSgSDyxq_GSHRzSHR0_r2_lF]] : $@convention(thin) <τ_0_0, τ_0_1, τ_0_2, τ_0_3 where τ_0_0 : Hashable, τ_0_2 : Hashable> (@guaranteed Dictionary<τ_0_0, τ_0_1>) -> @owned Optional<Dictionary<τ_0_2, τ_0_3>>
+  // CHECK-NEXT: [[RESULT:%[0-9]+]] = apply [[DICT_CAST_FN]]<String, BaseClass, String, DerivedClass>
+  // CHECK-NEXT: switch_enum [[RESULT]]
+  if case _ as [String : DerivedClass] = dict {}
+  // CHECK: [[DICT_CAST_FN:%[0-9]+]] = function_ref @$[[FN_REF]]
+  // CHECK-NEXT: [[RESULT:%[0-9]+]] = apply [[DICT_CAST_FN]]<String, BaseClass, String, DerivedClass>
+  // CHECK-NEXT: switch_enum [[RESULT]]
+  guard case _ as [String : DerivedClass] = dict else {}
+  // CHECK: [[DICT_CAST_FN:%[0-9]+]] = function_ref @$[[FN_REF]]
+  // CHECK-NEXT: [[RESULT:%[0-9]+]] = apply [[DICT_CAST_FN]]<String, BaseClass, String, DerivedClass>
+  // CHECK-NEXT: switch_enum [[RESULT]]
+  while case _ as [String : DerivedClass] = dict {}
+
+  // CHECK: [[DICT_CAST_FN:%[0-9]+]] = function_ref @$[[FN_REF]]
+  // CHECK-NEXT: [[RESULT:%[0-9]+]] = apply [[DICT_CAST_FN]]<String, BaseClass, String, DerivedClass>
+  // CHECK-NEXT: switch_enum [[RESULT]]
+  if case is [String : DerivedClass] = dict {}
+  // CHECK: [[DICT_CAST_FN:%[0-9]+]] = function_ref @$[[FN_REF]]
+  // CHECK-NEXT: [[RESULT:%[0-9]+]] = apply [[DICT_CAST_FN]]<String, BaseClass, String, DerivedClass>
+  // CHECK-NEXT: switch_enum [[RESULT]]
+  guard case is [String : DerivedClass] = dict else {}
+  // CHECK: [[DICT_CAST_FN:%[0-9]+]] = function_ref @$[[FN_REF]]
+  // CHECK-NEXT: [[RESULT:%[0-9]+]] = apply [[DICT_CAST_FN]]<String, BaseClass, String, DerivedClass>
+  // CHECK-NEXT: switch_enum [[RESULT]]
+  while case is [String : DerivedClass] = dict {}
+}
+// CHECK: } // end sil function '$s10statements36test_isa_pattern_dictionary_downcastyySDySSAA9BaseClassCGF'
+
+// CHECK-LABEL: sil hidden [ossa] @$s10statements29test_isa_pattern_set_downcastyyShyxGSHRzlF : $@convention(thin) <T where T : Hashable> (@guaranteed Set<T>) -> () {
+func test_isa_pattern_set_downcast<T: Hashable>(_ set: Set<T>) {
+  // CHECK: [[SET_CAST_FN:%[0-9]+]] = function_ref @$[[FN_REF:ss23_setDownCastConditionalyShyq_GSgShyxGSHRzSHR_r0_lF]] : $@convention(thin) <τ_0_0, τ_0_1 where τ_0_0 : Hashable, τ_0_1 : Hashable> (@guaranteed Set<τ_0_0>) -> @owned Optional<Set<τ_0_1>>
+  // CHECK-NEXT: [[RESULT:%[0-9]+]] = apply [[SET_CAST_FN]]<T, Bool>
+  // CHECK-NEXT: switch_enum [[RESULT]]
+  if case let t as Set<Bool> = set {}
+  // FIXME: Get rid of these warnings when https://github.com/apple/swift/issues/60808 is fixed
+  // expected-warning@-2 {{immutable value 't' was never used; consider replacing with '_' or removing it}}
+  // CHECK: [[SET_CAST_FN:%[0-9]+]] = function_ref @$[[FN_REF]]
+  // CHECK-NEXT: [[RESULT:%[0-9]+]] = apply [[SET_CAST_FN]]<T, Bool>
+  // CHECK-NEXT: switch_enum [[RESULT]]
+  guard case let t as Set<Bool> = set else {}
+  // expected-warning@-1 {{immutable value 't' was never used; consider replacing with '_' or removing it}}
+  // CHECK: [[SET_CAST_FN:%[0-9]+]] = function_ref @$[[FN_REF]]
+  // CHECK-NEXT: [[RESULT:%[0-9]+]] = apply [[SET_CAST_FN]]<T, Bool>
+  // CHECK-NEXT: switch_enum [[RESULT]]
+  while case let t as Set<Bool> = set {}
+  // expected-warning@-1 {{immutable value 't' was never used; consider replacing with '_' or removing it}}
+
+  // CHECK: [[SET_CAST_FN:%[0-9]+]] = function_ref @$[[FN_REF]]
+  // CHECK-NEXT: [[RESULT:%[0-9]+]] = apply [[SET_CAST_FN]]<T, Int>
+  // CHECK-NEXT: switch_enum [[RESULT]]
+  if case is Set<Int> = set {}
+  // CHECK: [[SET_CAST_FN:%[0-9]+]] = function_ref @$[[FN_REF]]
+  // CHECK-NEXT: [[RESULT:%[0-9]+]] = apply [[SET_CAST_FN]]<T, Int>
+  // CHECK-NEXT: switch_enum [[RESULT]]
+  guard case is Set<Int> = set else {}
+  // CHECK: [[SET_CAST_FN:%[0-9]+]] = function_ref @$[[FN_REF]]
+  // CHECK-NEXT: [[RESULT:%[0-9]+]] = apply [[SET_CAST_FN]]<T, Int>
+  // CHECK-NEXT: switch_enum [[RESULT]]
+  while case is Set<Int> = set {}
+}
+// CHECK: } // end sil function '$s10statements29test_isa_pattern_set_downcastyyShyxGSHRzlF'
+
 // CHECK-LABEL: sil hidden [ossa] @$s10statements22let_else_tuple_bindingyS2i_SitSgF
 func let_else_tuple_binding(_ a : (Int, Int)?) -> Int {
 

test/SILGen/switch.swift

@@ -635,6 +635,133 @@ func test_isa_class_2(x: B) -> AnyObject {
 }
 // CHECK: } // end sil function '$s6switch16test_isa_class_21xyXlAA1BC_tF'
 
+// https://github.com/apple/swift/issues/56139
+
+// CHECK-LABEL: sil hidden [ossa] @$s6switch31test_isa_pattern_array_downcast2psySayAA1P_pG_tF : $@convention(thin) (@guaranteed Array<any P>) -> () {
+func test_isa_pattern_array_downcast(ps: Array<P>) {
+  // CHECK: bb0(%0 : @guaranteed $Array<any P>):
+  switch ps {
+  // CHECK: checked_cast_addr_br copy_on_success Array<any P> in [[P:%[0-9]+]] : $*Array<any P> to Array<X> in {{%[0-9]+}} : $*Array<X>, [[IS_X:bb[0-9]+]], [[IS_NOT_X:bb[0-9]+]]
+  case is [X]:
+    // CHECK: [[IS_X]]:
+    // CHECK: function_ref @$s6switch1ayyF
+    a()
+    // CHECK: br [[CONT:bb[0-9]+]]
+
+  // CHECK: [[IS_NOT_X]]:
+  // CHECK: [[DEST:%[0-9]+]] = alloc_stack $Array<Y>
+  // CHECK-NEXT: checked_cast_addr_br copy_on_success Array<any P> in [[P:%[0-9]+]] : $*Array<any P> to Array<Y> in [[DEST]] : $*Array<Y>, [[IS_Y:bb[0-9]+]], [[IS_NOT_Y:bb[0-9]+]]
+  case let _ as [Y]:
+    // CHECK: [[IS_Y]]:
+    // CHECK-NEXT: load [take] [[DEST]] : $*Array<Y>
+    // CHECK: function_ref @$s6switch1byyF
+    b()
+    // CHECK: br [[CONT]]
+  default:
+    // CHECK: [[IS_NOT_Y]]:
+    // CHECK: function_ref @$s6switch1cyyF
+    c()
+    // CHECK: br [[CONT]]
+  }
+  // CHECK: [[CONT]]:
+  // CHECK: function_ref @$s6switch1dyyF
+  d()
+}
+// CHECK: } // end sil function '$s6switch31test_isa_pattern_array_downcast2psySayAA1P_pG_tF'
+
+// CHECK-LABEL: sil hidden [ossa] @$s6switch39test_isa_pattern_array_downcast_closureyyF : $@convention(thin) () -> () {
+// CHECK: function_ref @$s6switch39test_isa_pattern_array_downcast_closureyyFySayAA1P_pGcfU_
+// CHECK: } // end sil function '$s6switch39test_isa_pattern_array_downcast_closureyyF'
+func test_isa_pattern_array_downcast_closure() {
+// CHECK-LABEL: sil private [ossa] @$s6switch39test_isa_pattern_array_downcast_closureyyFySayAA1P_pGcfU_ : $@convention(thin) (@guaranteed Array<any P>) -> () {
+  let _ = { (ps: [P]) -> Void in
+    // CHECK: bb0(%0 : @guaranteed $Array<any P>):
+    switch ps {
+    // CHECK: [[DEST:%[0-9]+]] = alloc_stack $Array<X>
+    // CHECK-NEXT: checked_cast_addr_br copy_on_success Array<any P> in [[P:%[0-9]+]] : $*Array<any P> to Array<X> in [[DEST]] : $*Array<X>, [[IS_X:bb[0-9]+]], [[IS_NOT_X:bb[0-9]+]]
+    case let _ as [X]:
+      // CHECK: [[IS_X]]:
+      // CHECK-NEXT: load [take] [[DEST]] : $*Array<X>
+      // CHECK: function_ref @$s6switch1ayyF
+      a()
+      // CHECK: br [[CONT:bb[0-9]+]]
+
+    // CHECK: [[IS_NOT_X]]:
+    // CHECK: br [[DEF:bb[0-9]+]]
+    default:
+      // CHECK: [[DEF]]:
+      // CHECK: function_ref @$s6switch1byyF
+      b()
+      // CHECK: br [[CONT]]
+    }
+  }
+  // CHECK: } // end sil function '$s6switch39test_isa_pattern_array_downcast_closureyyFySayAA1P_pGcfU_'
+}
+
+// CHECK-LABEL: sil hidden [ossa] @$s6switch30test_isa_pattern_dict_downcast2psySDySSAA1P_pG_tF : $@convention(thin) (@guaranteed Dictionary<String, any P>) -> () {
+func test_isa_pattern_dict_downcast(ps: Dictionary<String, P>) {
+  // CHECK: bb0(%0 : @guaranteed $Dictionary<String, any P>):
+  switch ps {
+  // CHECK: checked_cast_addr_br copy_on_success Dictionary<String, any P> in [[P:%[0-9]+]] : $*Dictionary<String, any P> to Dictionary<String, X> in {{%[0-9]+}} : $*Dictionary<String, X>, [[IS_X:bb[0-9]+]], [[IS_NOT_X:bb[0-9]+]]
+  case is [String : X]:
+    // CHECK: [[IS_X]]:
+    // CHECK: function_ref @$s6switch1ayyF
+    a()
+    // CHECK: br [[CONT:bb[0-9]+]]
+
+  // CHECK: [[IS_NOT_X]]:
+  // CHECK: [[DEST:%[0-9]+]] = alloc_stack $Dictionary<String, Y>
+  // CHECK-NEXT: checked_cast_addr_br copy_on_success Dictionary<String, any P> in [[P:%[0-9]+]] : $*Dictionary<String, any P> to Dictionary<String, Y> in [[DEST]] : $*Dictionary<String, Y>, [[IS_Y:bb[0-9]+]], [[IS_NOT_Y:bb[0-9]+]]
+  case let _ as [String : Y]:
+    // CHECK: [[IS_Y]]:
+    // CHECK-NEXT: load [take] [[DEST]] : $*Dictionary<String, Y>
+    // CHECK: function_ref @$s6switch1byyF
+    b()
+    // CHECK: br [[CONT]]
+  default:
+    // CHECK: [[IS_NOT_Y]]:
+    // CHECK: function_ref @$s6switch1cyyF
+    c()
+    // CHECK: br [[CONT]]
+  }
+  // CHECK: [[CONT]]:
+  // CHECK: function_ref @$s6switch1dyyF
+  d()
+}
+// CHECK-LABEL: } // end sil function '$s6switch30test_isa_pattern_dict_downcast2psySDySSAA1P_pG_tF'
+
+// CHECK-LABEL: sil hidden [ossa] @$s6switch29test_isa_pattern_set_downcast2psyShyxG_tSHRzlF : $@convention(thin) <T where T : Hashable> (@guaranteed Set<T>) -> () {
+func test_isa_pattern_set_downcast<T: Hashable>(ps: Set<T>) {
+  // CHECK: bb0(%0 : @guaranteed $Set<T>):
+  switch ps {
+  // CHECK: checked_cast_addr_br copy_on_success Set<T> in [[P:%[0-9]+]] : $*Set<T> to Set<Int> in {{%[0-9]+}} : $*Set<Int>, [[IS_INT:bb[0-9]+]], [[IS_NOT_INT:bb[0-9]+]]
+  case is Set<Int>:
+    // CHECK: [[IS_INT]]:
+    // CHECK: function_ref @$s6switch1ayyF
+    a()
+    // CHECK: br [[CONT:bb[0-9]+]]
+
+  // CHECK: [[IS_NOT_INT]]:
+  // CHECK: [[DEST:%[0-9]+]] = alloc_stack $Set<Bool>
+  // CHECK-NEXT: checked_cast_addr_br copy_on_success Set<T> in [[P:%[0-9]+]] : $*Set<T> to Set<Bool> in [[DEST]] : $*Set<Bool>, [[IS_BOOL:bb[0-9]+]], [[IS_NOT_BOOL:bb[0-9]+]]
+  case let _ as Set<Bool>:
+    // CHECK: [[IS_BOOL]]:
+    // CHECK-NEXT: load [take] [[DEST]] : $*Set<Bool>
+    // CHECK: function_ref @$s6switch1byyF
+    b()
+    // CHECK: br [[CONT]]
+  default:
+    // CHECK: [[IS_NOT_BOOL]]:
+    // CHECK: function_ref @$s6switch1cyyF
+    c()
+    // CHECK: br [[CONT]]
+  }
+  // CHECK: [[CONT]]:
+  // CHECK: function_ref @$s6switch1dyyF
+  d()
+}
+// CHECK: } // end sil function '$s6switch29test_isa_pattern_set_downcast2psyShyxG_tSHRzlF'
+
 enum MaybePair {
   case Neither
   case Left(Int)