Expose More TypeChecker

* getUnionType
* getIntersectionType
* getTypeFromTypeReference

Author: aozgaa

src/compiler/checker.ts

@@ -81,6 +81,9 @@ namespace ts {
             getSignaturesOfType,
             getIndexTypeOfType,
             getBaseTypes,
+            getUnionType,
+            getIntersectionType,
+            getTypeFromTypeReference,
             getReturnTypeOfSignature,
             resolveStructuredTypeMembers,
             getNonNullableType,
@@ -2037,7 +2040,7 @@ namespace ts {
             return result || types;
         }
 
-        function visibilityToString(flags: ModifierFlags) {
+        function visibilityToString(flags: ModifierFlags): string | undefined {
             if (flags === ModifierFlags.Private) {
                 return "private";
             }

src/compiler/types.ts

@@ -2255,6 +2255,8 @@ namespace ts {
         resolveStructuredTypeMembers(type: StructuredType): ResolvedType;
         getReturnTypeOfSignature(signature: Signature): Type;
         getNonNullableType(type: Type): Type;
+        getIntersectionType(types: Type[], aliasSymbol?: Symbol, aliasTypeArguments?: Type[]): Type;
+        getUnionType(types: Type[], subtypeReduction?: boolean, aliasSymbol?: Symbol, aliasTypeArguments?: Type[]): Type;
 
         getSymbolsInScope(location: Node, meaning: SymbolFlags): Symbol[];
         getSymbolOfNode(node: Node): Symbol;
@@ -2264,6 +2266,7 @@ namespace ts {
         getExportSpecifierLocalTargetSymbol(location: ExportSpecifier): Symbol;
         getPropertySymbolOfDestructuringAssignment(location: Identifier): Symbol;
         getTypeAtLocation(node: Node): Type;
+        getTypeFromTypeReference(node: TypeReferenceNode | ExpressionWithTypeArguments | JSDocTypeReference): Type;
         typeToString(type: Type, enclosingDeclaration?: Node, flags?: TypeFormatFlags): string;
         symbolToString(symbol: Symbol, enclosingDeclaration?: Node, meaning?: SymbolFlags): string;
         getSymbolDisplayBuilder(): SymbolDisplayBuilder;