[Print as C++] Don't crash on sugared types

Author: DougGregor

lib/PrintAsClang/PrintClangFunction.cpp

@@ -152,7 +152,13 @@ class CFunctionSignatureTypePrinter
     if (printIfKnownSimpleType(alias, optionalKind, isInOutParam))
       return ClangRepresentation::representable;
 
-    return visitPart(aliasTy->getSinglyDesugaredType(), optionalKind,
+    return visitSugarType(aliasTy, optionalKind, isInOutParam);
+  }
+
+  ClangRepresentation visitSugarType(SugarType *sugarTy,
+                                     Optional<OptionalTypeKind> optionalKind,
+                                     bool isInOutParam) {
+    return visitPart(sugarTy->getSinglyDesugaredType(), optionalKind,
                      isInOutParam);
   }
 

test/PrintAsCxx/function_with_array.swift

@@ -0,0 +1,9 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend %s -typecheck -clang-header-expose-public-decls -emit-clang-header-path %t/function_with_array.h
+// RUN: %FileCheck %s < %t/function_with_array.h
+
+// CHECK: namespace function_with_array
+// FIXME: we don't actually emit a declaration for this, but for now at least
+// check that we don't crash.
+// CHECK-NOT: void f
+public func f(_: [Int]) { }