Infer lacked types of methods from bases

[falsandtru]

TypeScript Version: master

Code

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.

[ahejlsberg]

See #10610.

[falsandtru]

Thanks, I'll watch it.