Fix crash when generating IR for a dependent objc generic.

Author: Eshed Shaham

lib/AST/ClangTypeConverter.cpp

@@ -788,6 +788,10 @@ clang::QualType ClangTypeConverter::visitArchetypeType(ArchetypeType *type) {
   return getClangIdType(ClangASTContext);
 }
 
+clang::QualType ClangTypeConverter::visitDependentMemberType(DependentMemberType *type) {
+  return convert(type->getBase());
+}
+
 clang::QualType ClangTypeConverter::visitDynamicSelfType(DynamicSelfType *type) {
   // Dynamic Self is equivalent to 'instancetype', which is treated as
   // 'id' within the Objective-C type system.

lib/AST/ClangTypeConverter.h

@@ -126,6 +126,7 @@ class ClangTypeConverter :
   clang::QualType visitBuiltinIntegerType(BuiltinIntegerType *type);
   clang::QualType visitBuiltinFloatType(BuiltinFloatType *type);
   clang::QualType visitArchetypeType(ArchetypeType *type);
+  clang::QualType visitDependentMemberType(DependentMemberType *type);
   clang::QualType visitSILFunctionType(SILFunctionType *type);
   clang::QualType visitGenericTypeParamType(GenericTypeParamType *type);
   clang::QualType visitDynamicSelfType(DynamicSelfType *type);

test/IRGen/Inputs/objc_dependent_type_closure_argument.h

@@ -0,0 +1,7 @@
+@import Foundation;
+
+@interface ObjCClass<V> : NSObject
+
+- (void)barWithBlock:(nullable void (^)(V _Nullable))block;
+
+@end

test/IRGen/objc_dependent_type_closure_argument.swift

@@ -0,0 +1,12 @@
+// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -emit-ir -primary-file %s -enable-objc-interop -import-objc-header %S/Inputs/objc_dependent_type_closure_argument.h
+
+// Regression test for https://github.com/apple/swift/pull/40295
+public protocol SwiftProtocol {
+  associatedtype T: AnyObject
+}
+
+public class SwiftClass<S: SwiftProtocol> {
+  static func foo(objcClass: ObjCClass<S.T>) {
+    objcClass.bar(block: { _ in })
+  }
+}