Merge pull request #69771 from DougGregor/typed-throws-map

Replace rethrowing map with generic typed throws

Author: DougGregor

stdlib/public/core/Collection.swift

@@ -1190,9 +1190,10 @@ extension Collection {
   /// - Returns: An array containing the transformed elements of this
   ///   sequence.
   @inlinable
-  public func map<T>(
-    _ transform: (Element) throws -> T
-  ) rethrows -> [T] {
+  @_alwaysEmitIntoClient
+  public func map<T, E>(
+    _ transform: (Element) throws(E) -> T
+  ) throws(E) -> [T] {
     // TODO: swift-3-indexing-model - review the following
     let n = self.count
     if n == 0 {
@@ -1213,6 +1214,17 @@ extension Collection {
     return Array(result)
   }
 
+  // ABI-only entrypoint for the rethrows version of map, which has been
+  // superseded by the typed-throws version. Expressed as "throws", which is
+  // ABI-compatible with "rethrows".
+  @usableFromInline
+  @_silgen_name("$sSlsE3mapySayqd__Gqd__7ElementQzKXEKlF")
+  func __rethrows_map<T>(
+    _ transform: (Element) throws -> T
+  ) throws -> [T] {
+    try map(transform)
+  }
+
   /// Returns a subsequence containing all but the given number of initial
   /// elements.
   ///

stdlib/public/core/ExistentialCollection.swift

@@ -175,7 +175,7 @@ internal class _AnySequenceBox<Element> {
   @inlinable
   internal func _map<T>(
     _ transform: (Element) throws -> T
-  ) rethrows -> [T] {
+  ) throws -> [T] {
     _abstract()
   }
 
@@ -525,8 +525,8 @@ internal final class _SequenceBox<S: Sequence>: _AnySequenceBox<S.Element> {
   @inlinable
   internal override func _map<T>(
     _ transform: (Element) throws -> T
-  ) rethrows -> [T] {
-    return try _base.map(transform)
+  ) throws -> [T] {
+    try _base.map(transform)
   }
   @inlinable
   internal override func _filter(
@@ -618,8 +618,8 @@ internal final class _CollectionBox<S: Collection>: _AnyCollectionBox<S.Element>
   @inlinable
   internal override func _map<T>(
     _ transform: (Element) throws -> T
-  ) rethrows -> [T] {
-    return try _base.map(transform)
+  ) throws -> [T] {
+    try _base.map(transform)
   }
   @inlinable
   internal override func _filter(
@@ -813,8 +813,8 @@ internal final class _BidirectionalCollectionBox<S: BidirectionalCollection>
   @inlinable
   internal override func _map<T>(
     _ transform: (Element) throws -> T
-  ) rethrows -> [T] {
-    return try _base.map(transform)
+  ) throws -> [T] {
+    try _base.map(transform)
   }
   @inlinable
   internal override func _filter(
@@ -1026,8 +1026,8 @@ internal final class _RandomAccessCollectionBox<S: RandomAccessCollection>
   @inlinable
   internal override func _map<T>(
     _ transform: (Element) throws -> T
-  ) rethrows -> [T] {
-    return try _base.map(transform)
+  ) throws -> [T] {
+    try _base.map(transform)
   }
   @inlinable
   internal override func _filter(
@@ -1308,10 +1308,26 @@ extension AnySequence {
   }
 
   @inlinable
-  public func map<T>(
+  @_alwaysEmitIntoClient
+  public func map<T, E>(
+    _ transform: (Element) throws(E) -> T
+  ) throws(E) -> [T] {
+    do {
+      return try _box._map(transform)
+    } catch {
+      throw error as! E
+    }
+  }
+
+  // ABI-only entrypoint for the rethrows version of map, which has been
+  // superseded by the typed-throws version. Expressed as "throws", which is
+  // ABI-compatible with "rethrows".
+  @usableFromInline
+  @_silgen_name("$ss11AnySequenceV3mapySayqd__Gqd__xKXEKlF")
+  func __rethrows_map<T>(
     _ transform: (Element) throws -> T
-  ) rethrows -> [T] {
-    return try _box._map(transform)
+  ) throws -> [T] {
+    try map(transform)
   }
 
   @inlinable
@@ -1395,10 +1411,26 @@ extension AnyCollection {
   }
 
   @inlinable
-  public func map<T>(
+  @_alwaysEmitIntoClient
+  public func map<T, E>(
+    _ transform: (Element) throws(E) -> T
+  ) throws(E) -> [T] {
+    do {
+      return try _box._map(transform)
+    } catch {
+      throw error as! E
+    }
+  }
+
+  // ABI-only entrypoint for the rethrows version of map, which has been
+  // superseded by the typed-throws version. Expressed as "throws", which is
+  // ABI-compatible with "rethrows".
+  @usableFromInline
+  @_silgen_name("$ss13AnyCollectionV3mapySayqd__Gqd__xKXEKlF")
+  func __rethrows_map<T>(
     _ transform: (Element) throws -> T
-  ) rethrows -> [T] {
-    return try _box._map(transform)
+  ) throws -> [T] {
+    try map(transform)
   }
 
   @inlinable
@@ -1488,10 +1520,26 @@ extension AnyBidirectionalCollection {
   }
 
   @inlinable
-  public func map<T>(
+  @_alwaysEmitIntoClient
+  public func map<T, E>(
+    _ transform: (Element) throws(E) -> T
+  ) throws(E) -> [T] {
+    do {
+      return try _box._map(transform)
+    } catch {
+      throw error as! E
+    }
+  }
+
+  // ABI-only entrypoint for the rethrows version of map, which has been
+  // superseded by the typed-throws version. Expressed as "throws", which is
+  // ABI-compatible with "rethrows".
+  @usableFromInline
+  @_silgen_name("$ss26AnyBidirectionalCollectionV3mapySayqd__Gqd__xKXEKlF")
+  func __rethrows_map<T>(
     _ transform: (Element) throws -> T
-  ) rethrows -> [T] {
-    return try _box._map(transform)
+  ) throws -> [T] {
+    try map(transform)
   }
 
   @inlinable
@@ -1583,10 +1631,26 @@ extension AnyRandomAccessCollection {
   }
 
   @inlinable
-  public func map<T>(
+  @_alwaysEmitIntoClient
+  public func map<T, E>(
+    _ transform: (Element) throws(E) -> T
+  ) throws(E) -> [T] {
+    do {
+      return try _box._map(transform)
+    } catch {
+      throw error as! E
+    }
+  }
+
+  // ABI-only entrypoint for the rethrows version of map, which has been
+  // superseded by the typed-throws version. Expressed as "throws", which is
+  // ABI-compatible with "rethrows".
+  @usableFromInline
+  @_silgen_name("$ss25AnyRandomAccessCollectionV3mapySayqd__Gqd__xKXEKlF")
+  func __rethrows_map<T>(
     _ transform: (Element) throws -> T
-  ) rethrows -> [T] {
-    return try _box._map(transform)
+  ) throws -> [T] {
+    try map(transform)
   }
 
   @inlinable

stdlib/public/core/Misc.swift

@@ -159,6 +159,16 @@ public func _unsafePerformance<T>(_ c: () -> T) -> T {
   return c()
 }
 
+// Helper function that exploits a bug in rethrows checking to
+// allow us to call rethrows functions from generic typed-throws functions
+// and vice-versa.
+@usableFromInline
+@_alwaysEmitIntoClient
+@inline(__always)
+func _rethrowsViaClosure(_ fn: () throws -> ()) rethrows {
+  try fn()
+}
+
 #if $NoncopyableGenerics && $NonescapableTypes
 @_marker public protocol Copyable: ~Escapable {}
 @_marker public protocol Escapable: ~Copyable {}

stdlib/public/core/Sequence.swift

@@ -670,9 +670,10 @@ extension Sequence {
   ///
   /// - Complexity: O(*n*), where *n* is the length of the sequence.
   @inlinable
-  public func map<T>(
-    _ transform: (Element) throws -> T
-  ) rethrows -> [T] {
+  @_alwaysEmitIntoClient
+  public func map<T, E>(
+    _ transform: (Element) throws(E) -> T
+  ) throws(E) -> [T] {
     let initialCapacity = underestimatedCount
     var result = ContiguousArray<T>()
     result.reserveCapacity(initialCapacity)
@@ -690,6 +691,17 @@ extension Sequence {
     return Array(result)
   }
 
+  // ABI-only entrypoint for the rethrows version of map, which has been
+  // superseded by the typed-throws version. Expressed as "throws", which is
+  // ABI-compatible with "rethrows".
+  @usableFromInline
+  @_silgen_name("$sSTsE3mapySayqd__Gqd__7ElementQzKXEKlF")
+  func __rethrows_map<T>(
+    _ transform: (Element) throws -> T
+  ) throws -> [T] {
+    try map(transform)
+  }
+
   /// Returns an array containing, in order, the elements of the sequence
   /// that satisfy the given predicate.
   ///

test/Constraints/closures.swift

@@ -1143,11 +1143,11 @@ struct R_76250381<Result, Failure: Error> {
 
 // https://github.com/apple/swift/issues/55926
 (0..<10).map { x, y in } 
-// expected-error@-1 {{contextual closure type '(Range<Int>.Element) throws -> ()' (aka '(Int) throws -> ()') expects 1 argument, but 2 were used in closure body}}
+// expected-error@-1 {{contextual closure type '(Range<Int>.Element) -> ()' (aka '(Int) -> ()') expects 1 argument, but 2 were used in closure body}}
 (0..<10).map { x, y, z in } 
-// expected-error@-1 {{contextual closure type '(Range<Int>.Element) throws -> ()' (aka '(Int) throws -> ()') expects 1 argument, but 3 were used in closure body}}
+// expected-error@-1 {{contextual closure type '(Range<Int>.Element) -> ()' (aka '(Int) -> ()') expects 1 argument, but 3 were used in closure body}}
 (0..<10).map { x, y, z, w in } 
-// expected-error@-1 {{contextual closure type '(Range<Int>.Element) throws -> ()' (aka '(Int) throws -> ()') expects 1 argument, but 4 were used in closure body}}
+// expected-error@-1 {{contextual closure type '(Range<Int>.Element) -> ()' (aka '(Int) -> ()') expects 1 argument, but 4 were used in closure body}}
 
 // rdar://77022842 - crash due to a missing argument to a ternary operator
 func rdar77022842(argA: Bool? = nil, argB: Bool? = nil) {
@@ -1171,6 +1171,7 @@ func rdar76058892() {
     test { // expected-error {{contextual closure type '() -> String' expects 0 arguments, but 1 was used in closure body}}
       if let arr = arr {
         arr.map($0.test) // expected-note {{anonymous closure parameter '$0' is used here}} // expected-error {{generic parameter 'T' could not be inferred}}
+        // expected-error@-1 {{generic parameter 'E' could not be inferred}}
       }
     }
   }

test/Constraints/enum_cases.swift

@@ -19,14 +19,14 @@ enum G_E<T> {
 let arr: [String] = []
 let _ = arr.map(E.foo) // Ok
 let _ = arr.map(E.bar) // Ok
-let _ = arr.map(E.two) // expected-error {{cannot convert value of type '(Int, Int) -> E' to expected argument type '(String) throws -> E'}}
+let _ = arr.map(E.two) // expected-error {{cannot convert value of type '(Int, Int) -> E' to expected argument type '(String) -> E'}}
 
-let _ = arr.map(E.tuple) // expected-error {{cannot convert value of type '((x: Int, y: Int)) -> E' to expected argument type '(String) throws -> E'}}
+let _ = arr.map(E.tuple) // expected-error {{cannot convert value of type '((x: Int, y: Int)) -> E' to expected argument type '(String) -> E'}}
 
 let _ = arr.map(G_E<String>.foo) // Ok
 let _ = arr.map(G_E<String>.bar) // Ok
-let _ = arr.map(G_E<String>.two) // expected-error {{cannot convert value of type '(String, String) -> G_E<String>' to expected argument type '(String) throws -> G_E<String>'}}
-let _ = arr.map(G_E<Int>.tuple) // expected-error {{cannot convert value of type '((x: Int, y: Int)) -> G_E<Int>' to expected argument type '(String) throws -> G_E<Int>'}}
+let _ = arr.map(G_E<String>.two) // expected-error {{cannot convert value of type '(String, String) -> G_E<String>' to expected argument type '(String) -> G_E<String>'}}
+let _ = arr.map(G_E<Int>.tuple) // expected-error {{cannot convert value of type '((x: Int, y: Int)) -> G_E<Int>' to expected argument type '(String) -> G_E<Int>'}}
 
 let _ = E.foo("hello") // expected-error {{missing argument label 'bar:' in call}}
 let _ = E.bar("hello") // Ok

test/Constraints/tuple_arguments.swift

@@ -1726,7 +1726,7 @@ do {
 do {
   func f(_: Int...) {}
   let _ = [(1, 2, 3)].map(f) // expected-error {{no exact matches in call to instance method 'map'}}
-  // expected-note@-1 {{found candidate with type '(((Int, Int, Int)) throws -> _) throws -> Array<_>'}}
+  // expected-note@-1 {{found candidate with type '(((Int, Int, Int)) -> _) -> Array<_>'}}
 }
 
 // rdar://problem/48443263 - cannot convert value of type '() -> Void' to expected argument type '(_) -> Void'

test/IDE/complete_from_stdlib.swift

@@ -20,30 +20,30 @@ func protocolExtCollection1a<C : Collection>(_ a: C) {
   a.#^PRIVATE_NOMINAL_MEMBERS_2A?check=PRIVATE_NOMINAL_MEMBERS_2A;check=NEGATIVE_PRIVATE_NOMINAL_MEMBERS_2A;check=NO_STDLIB_PRIVATE^#
 }
 
-// PRIVATE_NOMINAL_MEMBERS_2A-DAG: Decl[InstanceMethod]/CurrNominal/IsSystem: map({#(transform): (C.Element) throws -> T##(C.Element) throws -> T#})[' rethrows'][#[T]#];
+// PRIVATE_NOMINAL_MEMBERS_2A-DAG: Decl[InstanceMethod]/CurrNominal/IsSystem: map({#(transform): (C.Element) throws(Error) -> T##(C.Element) throws(Error) -> T#})[' throws'][#[T]#];
 // NEGATIVE_PRIVATE_NOMINAL_MEMBERS_2A-NOT: Decl{{.*}}: index({#before: any Comparable#})
 
 func protocolExtCollection1b(_ a: Collection) {
   a.#^PRIVATE_NOMINAL_MEMBERS_2B?check=PRIVATE_NOMINAL_MEMBERS_2B;check=NEGATIVE_PRIVATE_NOMINAL_MEMBERS_2B;check=NO_STDLIB_PRIVATE^#
 }
 
 // FIXME(https://github.com/apple/swift/issues/65696): We should not be showing this because (1) it cannot be accessed on the existential (2) we don't have the syntax and features to represent the projected type sig anyway.
-// PRIVATE_NOMINAL_MEMBERS_2B-DAG: map({#(transform): (any Collection.Element) throws -> T##(any Collection.Element) throws -> T#})[' rethrows'][#[T]#]{{; name=.+}}
+// PRIVATE_NOMINAL_MEMBERS_2B-DAG: map({#(transform): (any Collection.Element) throws(Error) -> T##(any Collection.Element) throws(Error) -> T#})[' throws'][#[T]#]{{; name=.+}}
 // NEGATIVE_PRIVATE_NOMINAL_MEMBERS_2B-NOT: Decl{{.*}}: index({#before: any Comparable#})
 
 func protocolExtCollection2<C : Collection where C.Index : BidirectionalIndex>(_ a: C) {
   a.#^PRIVATE_NOMINAL_MEMBERS_3?check=PRIVATE_NOMINAL_MEMBERS_3;check=NEGATIVE_PRIVATE_NOMINAL_MEMBERS_3;check=NO_STDLIB_PRIVATE^#
 }
 
-// PRIVATE_NOMINAL_MEMBERS_3-DAG: Decl[InstanceMethod]/Super/IsSystem:         map({#(transform): (C.Element) throws -> T##(C.Element) throws -> T#})[' rethrows'][#[T]#]{{; name=.+}}
+// PRIVATE_NOMINAL_MEMBERS_3-DAG: Decl[InstanceMethod]/Super/IsSystem:         map({#(transform): (C.Element) throws(Error) -> T##(C.Element) throws(Error) -> T#})[' throws'][#[T]#]{{; name=.+}}
 // PRIVATE_NOMINAL_MEMBERS_3-DAG: Decl[InstanceVar]/Super/IsSystem:            lazy[#LazySequence<Collection>#]{{; name=.+}}
 // PRIVATE_NOMINAL_MEMBERS_3-DAG: firstIndex({#where: (C.Element) throws -> Bool##(C.Element) throws -> Bool#})[' rethrows'][#Comparable?#]{{; name=.+}}
 // NEGATIVE_PRIVATE_NOMINAL_MEMBERS_3-NOT: Decl{{.*}}:         firstIndex({#({{.*}}): Self.Iterator.Element
 
 func protocolExtArray<T : Equatable>(_ a: [T]) {
   a.#^PRIVATE_NOMINAL_MEMBERS_4?check=PRIVATE_NOMINAL_MEMBERS_4;check=NO_STDLIB_PRIVATE^#
 }
-// PRIVATE_NOMINAL_MEMBERS_4-DAG: Decl[InstanceMethod]/Super/IsSystem:         map({#(transform): (Equatable) throws -> T##(Equatable) throws -> T#})[' rethrows'][#[T]#]{{; name=.+}}
+// PRIVATE_NOMINAL_MEMBERS_4-DAG: Decl[InstanceMethod]/Super/IsSystem:         map({#(transform): (Equatable) throws(Error) -> T##(Equatable) throws(Error) -> T#})[' throws'][#[T]#]{{; name=.+}}
 // PRIVATE_NOMINAL_MEMBERS_4-DAG: Decl[InstanceVar]/Super/IsSystem:            last[#Equatable?#]{{; name=.+}}
 // PRIVATE_NOMINAL_MEMBERS_4-DAG: Decl[InstanceMethod]/Super/IsSystem:         firstIndex({#of: Equatable#})[#Int?#]{{; name=.+}}
 // PRIVATE_NOMINAL_MEMBERS_4-DAG: Decl[InstanceMethod]/Super/IsSystem:         firstIndex({#where: (Equatable) throws -> Bool##(Equatable) throws -> Bool#})[' rethrows'][#Int?#]{{; name=.+}}
@@ -85,7 +85,7 @@ func testArchetypeReplacement3 (_ a : [Int]) {
 // PRIVATE_NOMINAL_MEMBERS_7-DAG: Decl[InstanceMethod]/CurrNominal/IsSystem:   append({#(newElement): Int#})[#Void#]
 // PRIVATE_NOMINAL_MEMBERS_7-DAG: Decl[InstanceMethod]/Super/IsSystem:         removeLast()[#Int#]
 // PRIVATE_NOMINAL_MEMBERS_7-DAG: Decl[InstanceVar]/Super/IsSystem:            first[#Int?#]
-// PRIVATE_NOMINAL_MEMBERS_7-DAG: Decl[InstanceMethod]/Super/IsSystem:         map({#(transform): (Int) throws -> T##(Int) throws -> T#})[' rethrows'][#[T]#]
+// PRIVATE_NOMINAL_MEMBERS_7-DAG: Decl[InstanceMethod]/Super/IsSystem:         map({#(transform): (Int) throws(Error) -> T##(Int) throws(Error) -> T#})[' throws'][#[T]#]
 // PRIVATE_NOMINAL_MEMBERS_7-DAG: Decl[InstanceMethod]/Super/IsSystem:         dropLast({#(k): Int#})[#ArraySlice<Int>#]
 // PRIVATE_NOMINAL_MEMBERS_7-DAG: Decl[InstanceMethod]/Super/IsSystem:         elementsEqual({#(other): Sequence#}, {#by: (Int, Sequence.Element) throws -> Bool##(Int, Sequence.Element) throws -> Bool#})[' rethrows'][#Bool#]; name=elementsEqual(:by:)
 // PRIVATE_NOMINAL_MEMBERS_7-DAG: Decl[InstanceMethod]/Super/IsSystem:         elementsEqual({#(other): Sequence#})[#Bool#]; name=elementsEqual(:)

test/SILGen/function_conversion.swift

@@ -660,14 +660,14 @@ struct FunctionConversionParameterSubstToOrigReabstractionTest {
   }
 }
 
-// CHECK: sil {{.*}} [ossa] @$sS4SIgggoo_S2Ss11AnyHashableVyps5Error_pIegggrrzo_TR
+// CHECK: sil {{.*}} [ossa] @$sS4SIgggoo_S2Ss11AnyHashableVypIegggrr_TR
 // CHECK:  [[TUPLE:%.*]] = apply %4(%2, %3) : $@noescape @callee_guaranteed (@guaranteed String, @guaranteed String) -> (@owned String, @owned String)
 // CHECK:  ([[LHS:%.*]], [[RHS:%.*]]) = destructure_tuple [[TUPLE]]
 // CHECK:  [[ADDR:%.*]] = alloc_stack $String
 // CHECK:  store [[LHS]] to [init] [[ADDR]] : $*String
 // CHECK:  [[CVT:%.*]] = function_ref @$ss21_convertToAnyHashableys0cD0VxSHRzlF : $@convention(thin) <τ_0_0 where τ_0_0 : Hashable> (@in_guaranteed τ_0_0) -> @out AnyHashable
 // CHECK:  apply [[CVT]]<String>(%0, [[ADDR]])
-// CHECK: } // end sil function '$sS4SIgggoo_S2Ss11AnyHashableVyps5Error_pIegggrrzo_TR'
+// CHECK: } // end sil function '$sS4SIgggoo_S2Ss11AnyHashableVypIegggrr_TR'
 
 func dontCrash() {
   let userInfo = ["hello": "world"]

test/SILGen/opaque_values_silgen.swift

@@ -365,8 +365,16 @@ public struct EnumSeq<Base : Seq> : Seq {
 }
 
 extension Collection {
+  func myMap<T>(_ body: (Element) -> T) -> [T] {
+    var result = [T]()
+    for element in self {
+      result.append(body(element))
+    }
+    return result
+  }
+
   func transformEachElement<U>(_ cl: (Element) -> U) -> [U] {
-    return map(cl)
+    return myMap(cl)
   }
 }