**TypeScript Version:** master **Code** ```ts abstract class C { abstract m(a: number): void; } class D extends C { m(a) { // a should be number type } } ``` **Expected behavior:** **Actual behavior:** ``` $ node built/local/tsc.js index.ts --noImplicitAny --strictNullChecks index.ts(6,5): error TS7006: Parameter 'a' implicitly has an 'any' type. ```