Tests: Add Obj-C interop tests for ExtensionImportVisibility.

Author: tshortli

test/NameLookup/Inputs/Categories/Categories_A.h

@@ -0,0 +1,8 @@
+@import Foundation;
+
+@interface X
+@end
+
+@interface X (A)
+- (void)fromA;
+@end

test/NameLookup/Inputs/Categories/Categories_A.swift

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+@_exported import Categories_A
+
+extension X {
+  public func fromOverlayForA() {}
+  @objc public func fromOverlayForAObjC() {}
+}

test/NameLookup/Inputs/Categories/Categories_B.h

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+@import Categories_A;
+
+@interface X (B)
+- (void)fromB;
+@end

test/NameLookup/Inputs/Categories/Categories_B.swift

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+@_exported import Categories_B
+
+extension X {
+  public func fromOverlayForB() {}
+  @objc public func fromOverlayForBObjC() {}
+}

test/NameLookup/Inputs/Categories/Categories_C.h

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+@import Categories_A;
+
+@interface X (C)
+- (void)fromC;
+@end

test/NameLookup/Inputs/Categories/Categories_C.swift

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+@_exported import Categories_C
+
+extension X {
+  public func fromOverlayForC() {}
+  @objc public func fromOverlayForCObjC() {}
+}

test/NameLookup/Inputs/Categories/Categories_D.swift

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+import Categories_C

test/NameLookup/Inputs/Categories/module.modulemap

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+module Categories_A {
+  header "Categories_A.h"
+  export *
+}
+
+module Categories_B {
+  header "Categories_B.h"
+  export *
+}
+
+module Categories_C {
+  header "Categories_C.h"
+  export *
+}

test/NameLookup/extensions_transitive_objc.swift

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+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend -emit-module -I %t -I %S/Inputs/Categories -o %t %S/Inputs/Categories/Categories_A.swift
+// RUN: %target-swift-frontend -emit-module -I %t -I %S/Inputs/Categories -o %t %S/Inputs/Categories/Categories_B.swift
+// RUN: %target-swift-frontend -emit-module -I %t -I %S/Inputs/Categories -o %t %S/Inputs/Categories/Categories_C.swift
+// RUN: %target-swift-frontend -emit-module -I %t -I %S/Inputs/Categories -o %t %S/Inputs/Categories/Categories_D.swift
+// RUN: %target-swift-frontend -typecheck %s -I %t -I %S/Inputs/Categories -verify -enable-experimental-feature ExtensionImportVisibility
+
+// REQUIRES: objc_interop
+
+import Categories_B
+import Categories_D
+// expected-note 2 {{add import of module 'Categories_C'}}{{1-1=import Categories_C\n}}
+func test(x: X) {
+  x.fromA()
+  x.fromOverlayForA()
+  x.fromB()
+  x.fromOverlayForB()
+  x.fromC() // expected-error {{class method 'fromC()' is not available due to missing import of defining module 'Categories_C'}}
+  x.fromOverlayForC() // expected-error {{instance method 'fromOverlayForC()' is not available due to missing import of defining module 'Categories_C'}}
+}
+
+func testAnyObject(a: AnyObject) {
+  a.fromA()
+  a.fromOverlayForAObjC()
+  a.fromB()
+  a.fromOverlayForBObjC()
+  // FIXME: Better diagnostics?
+  // Name lookup for AnyObject already ignored transitive imports, so
+  // ExtensionImportVisibility has no effect on these diagnostics.
+  a.fromC() // expected-error {{value of type 'AnyObject' has no member 'fromC'}}
+  a.fromOverlayForCObjC() // expected-error {{value of type 'AnyObject' has no member 'fromOverlayForCObjC'}}
+}