Fix #28740 demangle constructors in stack traces (A.A becomes new A).

Regular constructors and unnamed factory constructors:
- Were A.A, now are new A
Named constructors (including factory constructors):
- Were A.A.name, now are new A.name

BUG=
R=asiva@google.com, rmacnak@google.com

Review-Url: https://codereview.chromium.org/2818933003 .

runtime/vm/object.cc

@@ -7175,11 +7175,16 @@ RawString* Function::QualifiedName(NameVisibility name_visibility) const {
   }
   const Class& cls = Class::Handle(Owner());
   if (!cls.IsTopLevel()) {
-    result = String::Concat(Symbols::Dot(), result, Heap::kOld);
-    const String& cls_name = String::Handle(name_visibility == kScrubbedName
-                                                ? cls.ScrubbedName()
-                                                : cls.UserVisibleName());
-    result = String::Concat(cls_name, result, Heap::kOld);
+    if (kind() == RawFunction::kConstructor) {
+      result = String::Concat(Symbols::ConstructorStacktracePrefix(), result,
+                              Heap::kOld);
+    } else {
+      result = String::Concat(Symbols::Dot(), result, Heap::kOld);
+      const String& cls_name = String::Handle(name_visibility == kScrubbedName
+                                                  ? cls.ScrubbedName()
+                                                  : cls.UserVisibleName());
+      result = String::Concat(cls_name, result, Heap::kOld);
+    }
   }
   return result.raw();
 }

runtime/vm/symbols.h

@@ -422,6 +422,7 @@ class ObjectPointerVisitor;
   V(removeLast, "removeLast")                                                  \
   V(add, "add")                                                                \
   V(ConstructorClosurePrefix, "new#")                                          \
+  V(ConstructorStacktracePrefix, "new ")                                       \
   V(_runExtension, "_runExtension")                                            \
   V(_runPendingImmediateCallback, "_runPendingImmediateCallback")              \
   V(DartLibrary, "dart.library.")                                              \

tests/language/language.status

@@ -233,6 +233,7 @@ map_literal4_test: SkipByDesign # Requires checked mode.
 
 vm/type_vm_test: Fail,OK  # Expects exact type name.
 
+stacktrace_demangle_ctors_test: SkipByDesign # Names are not scrubbed.
 
 [ ($compiler == none || $compiler == precompiler || $compiler == app_jit) && $browser ]
 # The following tests are supposed to fail.

tests/language/language_dart2js.status

@@ -55,6 +55,8 @@ covariant_test/32: MissingCompileTimeError, OK # Accepts `covariant` for statics
 covariant_test/34: MissingCompileTimeError, OK # Accepts `covariant` for statics/top-level.
 covariant_test/36: MissingCompileTimeError, OK # Accepts `covariant` for statics/top-level.
 
+stacktrace_demangle_ctors_test: Fail # dart2js stack traces are not always compliant.
+
 [ $compiler == dart2js && $fast_startup ]
 const_evaluation_test/*: Fail # mirrors not supported
 deferred_constraints_constants_test/none: Fail # mirrors not supported

tests/language/stacktrace_demangle_ctors_test.dart

@@ -0,0 +1,59 @@
+// Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// Test that stack traces are properly demangled in constructors (#28740).
+
+import "package:expect/expect.dart";
+
+class SomeClass {
+  SomeClass.namedConstructor() {
+    throw new Exception();
+  }
+
+  SomeClass() {
+    throw new Exception();
+  }
+
+  factory SomeClass.useFactory() {
+    throw new Exception();
+  }
+}
+
+class OnlyHasFactory {
+  factory OnlyHasFactory() {
+    throw new Exception();
+  }
+}
+
+void main() {
+  try {
+    new SomeClass();
+  } on Exception catch (e, st) {
+    final stString = st.toString();
+    Expect.isTrue(stString.contains("new SomeClass"));
+    Expect.isFalse(stString.contains("SomeClass."));
+  }
+
+  try {
+    new SomeClass.namedConstructor();
+  } on Exception catch (e, st) {
+    final stString = st.toString();
+    Expect.isTrue(stString.contains("new SomeClass.namedConstructor"));
+  }
+
+  try {
+    new OnlyHasFactory();
+  } on Exception catch (e, st) {
+    final stString = st.toString();
+    Expect.isTrue(stString.contains("new OnlyHasFactory"));
+    Expect.isFalse(stString.contains("OnlyHasFactory."));
+  }
+
+  try {
+    new SomeClass.useFactory();
+  } on Exception catch (e, st) {
+    final stString = st.toString();
+    Expect.isTrue(stString.contains("new SomeClass.useFactory"));
+  }
+}