change in types also makes reused module resolutions from old program

Author: sheetalkamat

src/compiler/program.ts

@@ -1349,7 +1349,7 @@ namespace ts {
             }
 
             if (!arrayIsEqualTo(options.types, oldOptions.types)) {
-                return StructureIsReused.Not;
+                return StructureIsReused.SafeModules;
             }
 
             // check if program source files has changed in the way that can affect structure of the program

src/testRunner/unittests/reuseProgramStructure.ts

@@ -262,7 +262,7 @@ namespace ts {
         it("fails if change affects type references", () => {
             const program1 = newProgram(files, ["a.ts"], { types: ["a"] });
             const program2 = updateProgram(program1, ["a.ts"], { types: ["b"] }, noop);
-            assert.equal(program2.structureIsReused, StructureIsReused.Not);
+            assert.equal(program2.structureIsReused, StructureIsReused.SafeModules);
         });
 
         it("succeeds if change doesn't affect type references", () => {