fix TF-489: stdlib ParseableInterface tests (swiftlang#27971)

Having `Array.DifferentiableView` only defined when `Element : Differentiable` makes the compiler quite confused, leading to issues like TF-489, TF-934.

This PR works around the issue by making `Array.DifferentiableView` unconstrained.

I reduced the problem to something that reproduces on master, and filed an issue for that: SR-11685. Once that issue is resolved, we can try reconstraining it.

Author: marcrasi

lib/AST/Type.cpp

@@ -3487,8 +3487,6 @@ TypeBase::getContextSubstitutions(const DeclContext *dc,
   if (auto *ownerClass = dyn_cast<ClassDecl>(ownerNominal))
     baseTy = baseTy->getSuperclassForDecl(ownerClass);
 
-  assert(ownerNominal == baseTy->getAnyNominal());
-
   // Gather all of the substitutions for all levels of generic arguments.
   auto genericSig = dc->getGenericSignatureOfContext();
   if (!genericSig)
@@ -3498,6 +3496,9 @@ TypeBase::getContextSubstitutions(const DeclContext *dc,
   unsigned n = params.size();
 
   while (baseTy && n > 0) {
+    if (baseTy->is<ErrorType>())
+      break;
+
     // For a bound generic type, gather the generic parameter -> generic
     // argument substitutions.
     if (auto boundGeneric = baseTy->getAs<BoundGenericType>()) {

stdlib/public/core/Array.swift

@@ -1911,54 +1911,50 @@ internal struct _ArrayAnyHashableBox<Element: Hashable>
 }
 
 // SWIFT_ENABLE_TENSORFLOW
-extension Array where Element : Differentiable {
+// TODO(TF-938): Add 'Element : Differentiable' constraint.
+extension Array {
   /// The view of an array as the differentiable product manifold of `Element`
   /// multiplied with itself `count` times.
   @frozen
-  public struct DifferentiableView : Differentiable {
-    private var _base: [Element]
-
-    /// The viewed array.
-    // I'm implementing this as a computed property instead of directly
-    // exposing `_base` because the `@differentiable` annotation does not make
-    // the stored property actually differentiable. I think this is a bug.
-    // Maybe it's related to `@frozen`?
-    // TODO: Determine if that is a bug, and fix.
-    public var base: [Element] {
-      @differentiable(wrt: self, vjp: _vjpBase)
-      get { return _base }
-      _modify { yield &_base }
-    }
+  public struct DifferentiableView {
+    var _base: [Element]
+  }
+}
 
-    @usableFromInline
-    func _vjpBase() ->
-      ([Element], (Array<Element>.TangentVector) -> TangentVector) {
-      return (base, { $0 })
-    }
+extension Array.DifferentiableView : Differentiable where Element : Differentiable {
+  /// The viewed array.
+  public var base: [Element] {
+    @differentiable(wrt: self, vjp: _vjpBase)
+    get { return _base }
+    _modify { yield &_base }
+  }
 
-    /// Creates a differentiable view of the given array.
-    @differentiable(wrt: base, vjp: _vjpInit)
-    public init(_ base: [Element]) { self._base = base }
+  @usableFromInline
+  func _vjpBase() ->
+    ([Element], (Array<Element>.TangentVector) -> TangentVector) {
+    return (base, { $0 })
+  }
 
-    @usableFromInline
-    static func _vjpInit(_ base: [Element]) ->
-      (Array.DifferentiableView, (TangentVector) -> TangentVector) {
-      return (Array.DifferentiableView(base), { $0 })
-    }
+  /// Creates a differentiable view of the given array.
+  @differentiable(wrt: base, vjp: _vjpInit)
+  public init(_ base: [Element]) { self._base = base }
 
-    // MARK: - Differentiable conformance.
+  @usableFromInline
+  static func _vjpInit(_ base: [Element]) ->
+    (Array.DifferentiableView, (TangentVector) -> TangentVector) {
+    return (Array.DifferentiableView(base), { $0 })
+  }
 
-    public typealias TangentVector =
-      Array<Element.TangentVector>.DifferentiableView
+  public typealias TangentVector =
+    Array<Element.TangentVector>.DifferentiableView
 
-    public mutating func move(along direction: TangentVector) {
-      precondition(
-        base.count == direction.base.count,
-        "cannot move Array.DifferentiableView with count \(base.count) along " +
-          "direction with different count \(direction.base.count)")
-      for i in base.indices {
-        base[i].move(along: direction.base[i])
-      }
+  public mutating func move(along direction: TangentVector) {
+    precondition(
+      base.count == direction.base.count,
+      "cannot move Array.DifferentiableView with count \(base.count) along " +
+        "direction with different count \(direction.base.count)")
+    for i in base.indices {
+      base[i].move(along: direction.base[i])
     }
   }
 }

stdlib/public/core/KeyPathIterable.swift

@@ -104,13 +104,20 @@ extension Array : KeyPathIterable {
   }
 }
 
-extension Array.DifferentiableView : KeyPathIterable {
+// TODO(TF-938): Remove 'Element : Differentiable' constraint.
+extension Array.DifferentiableView : KeyPathIterable where Element : Differentiable {
   public typealias AllKeyPaths = [PartialKeyPath<Array.DifferentiableView>]
   public var allKeyPaths: [PartialKeyPath<Array.DifferentiableView>] {
     return [\Array.DifferentiableView.base]
   }
 }
 
+// TODO(TF-938): Remove this.
+// This is neccessary now because otherwise the compiler complains:
+//   error: conditional conformance of type 'Array<Element>.DifferentiableView' to protocol
+//   'KeyPathIterable' does not imply conformance to inherited protocol '_KeyPathIterableBase'
+extension Array.DifferentiableView : _KeyPathIterableBase where Element : Differentiable {}
+
 extension Dictionary : KeyPathIterable {
   public typealias AllKeyPaths = [PartialKeyPath<Dictionary>]
   public var allKeyPaths: [PartialKeyPath<Dictionary>] {

utils/update_checkout/update-checkout-config.json

@@ -489,7 +489,7 @@
                 "clang-tools-extra": "swift-DEVELOPMENT-SNAPSHOT-2019-10-13-a",
                 "libcxx": "swift-DEVELOPMENT-SNAPSHOT-2019-10-13-a",
                 "tensorflow": "7c7d924821a8b1b20433c2f3f484bbd409873a84",
-                "tensorflow-swift-apis": "f4f88d924d71eedb0709e26d0d5e4b7cfe94d830",
+                "tensorflow-swift-apis": "e70b979b7a3c2ebd38457b8d4058a0b310b4e4b0",
                 "tensorflow-swift-quote": "62c0a88dc64a201497a66cbbc087c0c7771edabc",
                 "indexstore-db": "swift-DEVELOPMENT-SNAPSHOT-2019-10-13-a",
                 "sourcekit-lsp": "swift-DEVELOPMENT-SNAPSHOT-2019-10-13-a"

validation-test/ParseableInterface/verify_all_overlays.py

@@ -50,7 +50,8 @@
         continue
 
     # SWIFT_ENABLE_TENSORFLOW
-    # FIXME(TF-489): Re-enable this test after fixing `.swiftinterface` errors.
+    # TODO(TF-939): Enable this on DifferentiationUnittest, Python, and
+    # TensorFlow.
     if module_name in ["Swift", "SwiftLang", "DifferentiationUnittest", "Python", "TensorFlow"]:
         continue
 

validation-test/ParseableInterface/verify_stdlib.swift

@@ -1,10 +1,6 @@
 // Note that this test should still "pass" when Swift.swiftinterface has not
 // been generated.
 
-// SWIFT_ENABLE_TENSORFLOW
-// FIXME(TF-489): Re-enable this test after fixing `.swiftinterface` errors.
-// UNSUPPORTED: nonexecutable_test
-
 // RUN: %empty-directory(%t)
 // RUN: not ls %platform-module-dir/Swift.swiftmodule/%target-cpu.swiftinterface || %target-swift-frontend -build-module-from-parseable-interface %platform-module-dir/Swift.swiftmodule/%target-cpu.swiftinterface -parse-stdlib -o %t/Swift.swiftmodule