cache type for empty type literal (#11934)

cache type for empty type literal
microsoft · Oct 29, 2016 · 44ce59d · 44ce59d
1 parent 980f9fd
commit 44ce59d
Showing 1 changed file with 17 additions and 4 deletions.
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
@@ -138,6 +138,11 @@ namespace ts {
         const silentNeverType = createIntrinsicType(TypeFlags.Never, "never");
 
         const emptyObjectType = createAnonymousType(undefined, emptySymbols, emptyArray, emptyArray, undefined, undefined);
+
+        const emptyTypeLiteralSymbol = createSymbol(SymbolFlags.TypeLiteral | SymbolFlags.Transient, "__type");
+        emptyTypeLiteralSymbol.members = createMap<Symbol>();
+        const emptyTypeLiteralType = createAnonymousType(emptyTypeLiteralSymbol, emptySymbols, emptyArray, emptyArray, undefined, undefined);
+
         const emptyGenericType = <GenericType><ObjectType>createAnonymousType(undefined, emptySymbols, emptyArray, emptyArray, undefined, undefined);
         emptyGenericType.instantiations = createMap<TypeReference>();
 
@@ -5696,10 +5701,15 @@ namespace ts {
             const links = getNodeLinks(node);
             if (!links.resolvedType) {
                 // Deferred resolution of members is handled by resolveObjectTypeMembers
-                const type = createObjectType(ObjectFlags.Anonymous, node.symbol);
-                type.aliasSymbol = aliasSymbol;
-                type.aliasTypeArguments = aliasTypeArguments;
-                links.resolvedType = type;
+                if (isEmpty(node.symbol.members) && !aliasSymbol && !aliasTypeArguments) {
+                    links.resolvedType = emptyTypeLiteralType;
+                }
+                else {
+                    const type = createObjectType(ObjectFlags.Anonymous, node.symbol);
+                    type.aliasSymbol = aliasSymbol;
+                    type.aliasTypeArguments = aliasTypeArguments;
+                    links.resolvedType = type;
+                }
             }
             return links.resolvedType;
         }
@@ -6036,6 +6046,9 @@ namespace ts {
         }
 
         function isSymbolInScopeOfMappedTypeParameter(symbol: Symbol, mapper: TypeMapper) {
+            if (!(symbol.declarations && symbol.declarations.length)) {
+                return false;
+            }
             const mappedTypes = mapper.mappedTypes;
             // Starting with the parent of the symbol's declaration, check if the mapper maps any of
             // the type parameters introduced by enclosing declarations. We just pick the first