[NFC] Add skeleton of module selector lookup test

The diagnostics in this test will evolve as we implement pieces of the feature.

Author: beccadax

test/NameLookup/Inputs/ModuleSelectorTestingKit.swiftinterface

@@ -0,0 +1,42 @@
+// swift-interface-format-version: 1.0
+// swift-module-flags: -module-name ModuleSelectorTestingKit -swift-version 5
+
+import Swift
+
+// These types are identical; we just use them to test with different scope
+// selectors.
+
+public struct A {
+  public init(value: Swift.Int)
+  public dynamic mutating func negate()
+  public var magnitude: Swift.UInt
+}
+
+public struct B {
+  public init(value: Swift.Int)
+  public dynamic mutating func negate()
+  public var magnitude: Swift.UInt
+}
+
+public struct C {
+  public init(value: Int)
+  public dynamic mutating func negate()
+  public var magnitude: Swift.UInt
+}
+
+public struct D {
+  public init(value: Int)
+  public dynamic mutating func negate()
+  public var magnitude: Swift.UInt
+}
+
+@propertyWrapper
+public struct available {
+  public init() {}
+  public var wrappedValue: Int { 0 }
+}
+
+@_functionBuilder
+public struct MyBuilder {
+  public static func buildBlock()
+}

test/NameLookup/module_selector.swift

@@ -0,0 +1,263 @@
+// RUN: %target-typecheck-verify-swift -sdk %clang-importer-sdk -module-name main -I %S/Inputs -enable-experimental-feature ModuleSelector
+// RUN: %target-typecheck-verify-swift -sdk %clang-importer-sdk -module-name main -I %S/Inputs -enable-experimental-feature ModuleSelector -enable-experimental-feature ParserASTGen
+
+// REQUIRES: swift_feature_ModuleSelector, swift_feature_ParserASTGen
+
+// FIXME: This test doesn't really cover:
+//
+// * Whether X::foo finds foos in X's re-exports
+// * Whether we handle access paths correctly
+// * Interaction with ClangImporter
+// * Cross-import overlays
+// * Key paths
+// * Key path dynamic member lookup
+// * Custom type attributes (and coverage of type attrs generally is sparse)
+// * Macros
+//
+// It also might not cover all combinations of name lookup paths and inputs.
+
+import ModuleSelectorTestingKit
+
+import ctypes.bits
+import struct ModuleSelectorTestingKit::A
+
+let magnitude: Never = fatalError()
+
+// Test correct code using `A`
+
+extension ModuleSelectorTestingKit::A {}
+
+extension A: @retroactive Swift::Equatable {
+  @_implements(Swift::Equatable, ==(_:_:))
+  public static func equals(_: ModuleSelectorTestingKit::A, _: ModuleSelectorTestingKit::A) -> Swift::Bool {
+    Swift::fatalError()
+  }
+
+  // FIXME: Add tests with autodiff @_differentiable(jvp:vjp:) and
+  // @_derivative(of:)
+
+  @_dynamicReplacement(for: ModuleSelectorTestingKit::negate())
+  mutating func myNegate() {
+    let fn: (Swift::Int, Swift::Int) -> Swift::Int = (Swift::+)
+
+    let magnitude: Int.Swift::Magnitude = main::magnitude
+
+    _ = (fn, magnitude)
+
+    if Swift::Bool.Swift::random() {
+      self.ModuleSelectorTestingKit::negate()
+    }
+    else {
+      self = ModuleSelectorTestingKit::A(value: .Swift::min)
+      self = A.ModuleSelectorTestingKit::init(value: .min)
+    }
+
+    self.main::myNegate()
+
+    Swift::fatalError()
+  }
+
+  // FIXME: Can we test @convention(witness_method:)?
+}
+
+// Test resolution of main:: using `B`
+
+extension main::B {}
+
+extension B: @retroactive main::Equatable {
+
+  @_implements(main::Equatable, ==(_:_:))
+
+  public static func equals(_: main::B, _: main::B) -> main::Bool {
+    main::fatalError()
+  }
+
+  // FIXME: Add tests with autodiff @_differentiable(jvp:vjp:) and
+  // @_derivative(of:)
+
+  @_dynamicReplacement(for: main::negate())
+
+  mutating func myNegate() {
+    let fn: (main::Int, main::Int) -> main::Int =
+      (main::+)
+
+    let magnitude: Int.main::Magnitude = main::magnitude
+
+    _ = (fn, magnitude)
+
+    if main::Bool.main::random() {
+
+      main::negate()
+    }
+    else {
+      self = main::B(value: .main::min)
+
+      self = B.main::init(value: .min)
+    }
+
+    self.main::myNegate()
+
+    main::fatalError()
+  }
+
+  // FIXME: Can we test @convention(witness_method:)?
+}
+
+// Test resolution of ModuleSelectorTestingKit:: using `C`
+
+extension ModuleSelectorTestingKit::C {}
+
+extension C: @retroactive ModuleSelectorTestingKit::Equatable {
+
+  @_implements(ModuleSelectorTestingKit::Equatable, ==(_:_:))
+
+  public static func equals(_: ModuleSelectorTestingKit::C, _: ModuleSelectorTestingKit::C) -> ModuleSelectorTestingKit::Bool {
+    ModuleSelectorTestingKit::fatalError()
+  }
+
+  // FIXME: Add tests with autodiff @_differentiable(jvp:vjp:) and
+  // @_derivative(of:)
+
+  @_dynamicReplacement(for: ModuleSelectorTestingKit::negate())
+
+  mutating func myNegate() {
+    let fn: (ModuleSelectorTestingKit::Int, ModuleSelectorTestingKit::Int) -> ModuleSelectorTestingKit::Int =
+      (ModuleSelectorTestingKit::+)
+
+    let magnitude: Int.ModuleSelectorTestingKit::Magnitude = ModuleSelectorTestingKit::magnitude
+
+    _ = (fn, magnitude)
+
+    if ModuleSelectorTestingKit::Bool.ModuleSelectorTestingKit::random() {
+
+      ModuleSelectorTestingKit::negate()
+    }
+    else {
+      self = ModuleSelectorTestingKit::C(value: .ModuleSelectorTestingKit::min)
+
+      self = C.ModuleSelectorTestingKit::init(value: .min)
+    }
+
+    self.ModuleSelectorTestingKit::myNegate()
+
+    ModuleSelectorTestingKit::fatalError()
+  }
+
+  // FIXME: Can we test @convention(witness_method:)?
+}
+
+// Test resolution of Swift:: using `D`
+
+extension Swift::D {}
+
+extension D: @retroactive Swift::Equatable {
+
+  @_implements(Swift::Equatable, ==(_:_:))
+  public static func equals(_: Swift::D, _: Swift::D) -> Swift::Bool {
+    Swift::fatalError()
+  }
+
+  // FIXME: Add tests with autodiff @_differentiable(jvp:vjp:) and
+  // @_derivative(of:)
+
+  @_dynamicReplacement(for: Swift::negate())
+
+  mutating func myNegate() {
+
+    let fn: (Swift::Int, Swift::Int) -> Swift::Int =
+      (Swift::+)
+
+    let magnitude: Int.Swift::Magnitude = Swift::magnitude
+
+    _ = (fn, magnitude)
+
+    if Swift::Bool.Swift::random() {
+
+      Swift::negate()
+    }
+    else {
+      self = Swift::D(value: .Swift::min)
+
+      self = D.Swift::init(value: .min)
+    }
+
+    self.Swift::myNegate()
+
+    Swift::fatalError()
+  }
+
+  // FIXME: Can we test @convention(witness_method:)?
+}
+
+let mog: Never = fatalError()
+
+func localVarsCantBeAccessedByModuleSelector() {
+  let mag: Int.Swift::Magnitude = main::mag
+  // expected-error@-1 {{use of local variable 'mag' before its declaration}}
+  // expected-note@-2 {{'mag' declared here}}
+
+  let mog: Never = main::mog
+}
+
+struct AvailableUser {
+  @available(macOS 10.15, *) var use1: String { "foo" }
+
+  @main::available() var use2
+
+  @ModuleSelectorTestingKit::available() var use4
+  // no-error
+
+  @Swift::available() var use5
+}
+
+func builderUser2(@main::MyBuilder fn: () -> Void) {}
+
+func builderUser3(@ModuleSelectorTestingKit::MyBuilder fn: () -> Void) {}
+
+func builderUser4(@Swift::MyBuilder fn: () -> Void) {}
+
+// Error cases
+
+func decl1(
+  p1: main::A,
+  label p2: inout A,
+  label p3: @escaping () -> A
+) {
+  switch Optional(main::p2) {
+  case Optional.some(let decl1i):
+    // expected-warning@-1 {{immutable value 'decl1i' was never used; consider replacing with '_' or removing it}}
+    break
+  case .none:
+    break
+  }
+
+  switch Optional(main::p2) {
+  case let Optional.some(decl1j):
+    // expected-warning@-1 {{immutable value 'decl1j' was never used; consider replacing with '_' or removing it}}
+    break
+  case .none:
+    break
+  }
+
+  switch Optional(main::p2) {
+ case let decl1k?:
+    // expected-warning@-1 {{immutable value 'decl1k' was never used; consider replacing with '_' or removing it}}
+    break
+  case .none:
+    break
+  }
+}
+
+typealias decl5 = main::Bool
+
+func badModuleNames() {
+  NonexistentModule::print()
+
+  _ = "foo".NonexistentModule::count
+
+  let x: NonexistentModule::MyType = NonexistentModule::MyType()
+  // expected-error@-1 {{cannot find type 'MyType' in scope}}
+
+  let y: A.NonexistentModule::MyChildType = fatalError()
+  // expected-error@-1 {{'MyChildType' is not a member type of struct 'ModuleSelectorTestingKit.A'}}
+}