Suggestion: output fewer errors for incorrectly implemented interface

**TypeScript Version:** nightly **Code** ``` ts interface A { f(): void; } class B implements A { eff() {} } var b: B; b.f(); b.f(); b.f(); ``` **Expected behavior:** ``` src/a.ts(4,7): error TS2420: Class 'B' incorrectly implements interface 'A'. Property 'f' is missing in type 'B'. ``` **Actual behavior:** ``` src/a.ts(4,7): error TS2420: Class 'B' incorrectly implements interface 'A'. Property 'f' is missing in type 'B'. src/a.ts(9,3): error TS2339: Property 'f' does not exist on type 'B'. src/a.ts(10,3): error TS2339: Property 'f' does not exist on type 'B'. src/a.ts(11,3): error TS2339: Property 'f' does not exist on type 'B'. ``` There can be an overwhelming number of missing-property errors if a commonly-used class mis-implements an interface it declares.