Soften objcImpl selector conflict errors

lib/Sema/TypeCheckDeclObjC.cpp

@@ -2551,6 +2551,12 @@ bool swift::diagnoseObjCMethodConflicts(SourceFile &sf) {
                                      conflict.selector);
       diag.warnUntilSwiftVersionIf(breakingInSwift5, 6);
 
+      // Temporarily soften selector conflicts in objcImpl extensions; we're
+      // seeing some that are caused by ObjCImplementationChecker improvements.
+      if (conflictingDecl->getDeclContext()->getImplementedObjCContext()
+            != conflictingDecl->getDeclContext())
+        diag.wrapIn(diag::wrap_objc_implementation_will_become_error);
+
       auto objcAttr = getObjCAttrIfFromAccessNote(conflictingDecl);
       swift::softenIfAccessNote(conflictingDecl, objcAttr, diag);
       if (objcAttr)

test/decl/ext/Inputs/objc_implementation_class_extension.h

@@ -0,0 +1,21 @@
+@import Foundation;
+
+@interface ObjCClass : NSObject
+
+- (void)methodFromHeader1:(int)param;
+- (void)methodFromHeader2:(int)param;
+
+@property (readwrite) int propertyFromHeader1;
+@property (readwrite) int propertyFromHeader2;
+
+@end
+
+@interface ObjCClass ()
+
+- (void)extensionMethodFromHeader1:(int)param;
+- (void)extensionMethodFromHeader2:(int)param;
+
+@property (readwrite) int extensionPropertyFromHeader1;
+@property (readwrite) int extensionPropertyFromHeader2;
+
+@end

test/decl/ext/Inputs/objc_implementation_class_extension.modulemap

@@ -0,0 +1,9 @@
+module objc_implementation_class_extension {
+  header "objc_implementation_class_extension.h"
+  export *
+}
+
+module objc_implementation_class_extension_internal {
+  header "objc_implementation_class_extension_internal.h"
+  export *
+}

test/decl/ext/Inputs/objc_implementation_class_extension_internal.h

@@ -0,0 +1,11 @@
+#import "objc_implementation_class_extension.h"
+
+@interface ObjCClass ()
+
+- (void)otherModuleExtensionMethodFromHeader1:(int)param;
+- (void)otherModuleExtensionMethodFromHeader2:(int)param;
+
+@property (readwrite) int otherModuleExtensionPropertyFromHeader1;
+@property (readwrite) int otherModuleExtensionPropertyFromHeader2;
+
+@end

test/decl/ext/objc_implementation_class_extension.swift

@@ -0,0 +1,33 @@
+// RUN: %target-typecheck-verify-swift -verify-ignore-unknown -import-underlying-module -Xcc -fmodule-map-file=%S/Inputs/objc_implementation_class_extension.modulemap
+// REQUIRES: objc_interop
+
+@_implementationOnly import objc_implementation_class_extension_internal
+
+@_objcImplementation extension ObjCClass {
+  // expected-warning@-1 {{extension for main class interface should provide implementation for instance method 'method(fromHeader2:)'}}
+  // expected-warning@-2 {{extension for main class interface should provide implementation for property 'propertyFromHeader2'}}
+  // expected-warning@-3 {{extension for main class interface should provide implementation for instance method 'otherModuleExtensionMethod(fromHeader2:)'}}
+  // expected-warning@-4 {{extension for main class interface should provide implementation for property 'otherModuleExtensionPropertyFromHeader2'}}
+  // expected-warning@-5 {{extension for main class interface should provide implementation for instance method 'extensionMethod(fromHeader2:)'}}
+  // expected-warning@-6 {{extension for main class interface should provide implementation for property 'extensionPropertyFromHeader2'}}
+
+  @objc func method(fromHeader1: CInt) {}
+  @objc private func method(fromHeader2: CInt) {}
+
+  @objc var propertyFromHeader1: CInt = 1
+  @objc private var propertyFromHeader2: CInt = 2
+
+  @objc func extensionMethod(fromHeader1: CInt) {}
+  @objc private func extensionMethod(fromHeader2: CInt) {}
+
+  @objc var extensionPropertyFromHeader1: CInt = 1
+  @objc private var extensionPropertyFromHeader2: CInt = 2
+
+  @objc func otherModuleExtensionMethod(fromHeader1: CInt) {}
+  @objc private func otherModuleExtensionMethod(fromHeader2: CInt) {}
+
+  @objc var otherModuleExtensionPropertyFromHeader1: CInt = 1
+  @objc private var otherModuleExtensionPropertyFromHeader2: CInt = 2
+  // expected-warning@-1 {{getter for 'otherModuleExtensionPropertyFromHeader2' with Objective-C selector 'otherModuleExtensionPropertyFromHeader2' conflicts with previous declaration with the same Objective-C selector}}
+  // expected-warning@-2 {{setter for 'otherModuleExtensionPropertyFromHeader2' with Objective-C selector 'setOtherModuleExtensionPropertyFromHeader2:' conflicts with previous declaration with the same Objective-C selector}}
+}