From 6cd5a4dac9599122eff78d016a82ac0d362850ab Mon Sep 17 00:00:00 2001
From: Nathan Shively-Sanders <nathansa@microsoft.com>
Date: Thu, 10 Dec 2015 11:03:45 -0800
Subject: [PATCH] Compare enums semi-structurally.

1. Unqualified names must match.
2. Target contains members with same names as all source members.
---
 src/compiler/checker.ts | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 50a3aee995..0f04daf298 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -5040,6 +5040,11 @@ namespace ts {
                 if (source === undefinedType) return Ternary.True;
                 if (source === nullType && target !== undefinedType) return Ternary.True;
                 if (source.flags & TypeFlags.Enum && target === numberType) return Ternary.True;
+                if (source.flags & TypeFlags.Enum && target.flags & TypeFlags.Enum) {
+                    if (result = enumRelatedTo(source, target)) {
+                        return result;
+                    }
+                }
                 if (source.flags & TypeFlags.StringLiteral && target === stringType) return Ternary.True;
                 if (relation === assignableRelation) {
                     if (isTypeAny(source)) return Ternary.True;
@@ -5750,6 +5755,25 @@ namespace ts {
                 }
                 return Ternary.False;
             }
+
+            function enumRelatedTo(source: Type, target: Type) {
+                if (source.symbol.name !== target.symbol.name) {
+                    return Ternary.False;
+                }
+                const sourceDecl = <EnumDeclaration>getMergedSymbol(source.symbol).valueDeclaration;
+                const targetDecl = <EnumDeclaration>getMergedSymbol(target.symbol).valueDeclaration;
+                const targetMembers = arrayToMap(targetDecl.members, member => getTextOfPropertyName(<PropertyName>member.name));
+                for (const member of sourceDecl.members) {
+                    const name = getTextOfPropertyName(<PropertyName>member.name);
+                    if (!targetMembers[name]) {
+                        reportError(Diagnostics.Property_0_is_missing_in_type_1,
+                                    name,
+                                    typeToString(target, /*enclosingDeclaration*/ undefined, TypeFormatFlags.UseFullyQualifiedType));
+                        return Ternary.False;
+                    }
+                }
+                return Ternary.True;
+            }
         }
 
         // Return true if the given type is part of a deeply nested chain of generic instantiations. We consider this to be the case