=== tests/cases/compiler/classImplementsClass3.ts ===
class A { foo(): number { return 1; } }
>A : A, Symbol(A, Decl(classImplementsClass3.ts, 0, 0))
>foo : () => number, Symbol(foo, Decl(classImplementsClass3.ts, 0, 9))
>1 : number

class C implements A {
>C : C, Symbol(C, Decl(classImplementsClass3.ts, 0, 39))
>A : A, Symbol(A, Decl(classImplementsClass3.ts, 0, 0))

    foo() {
>foo : () => number, Symbol(foo, Decl(classImplementsClass3.ts, 1, 22))

        return 1;
>1 : number
    }
}

class C2 extends A {}
>C2 : C2, Symbol(C2, Decl(classImplementsClass3.ts, 5, 1))
>A : A, Symbol(A, Decl(classImplementsClass3.ts, 0, 0))

// no errors
var c: C;
>c : C, Symbol(c, Decl(classImplementsClass3.ts, 10, 3))
>C : C, Symbol(C, Decl(classImplementsClass3.ts, 0, 39))

var c2: C2;
>c2 : C2, Symbol(c2, Decl(classImplementsClass3.ts, 11, 3))
>C2 : C2, Symbol(C2, Decl(classImplementsClass3.ts, 5, 1))

c = c2;
>c = c2 : C2
>c : C, Symbol(c, Decl(classImplementsClass3.ts, 10, 3))
>c2 : C2, Symbol(c2, Decl(classImplementsClass3.ts, 11, 3))

c2 = c;
>c2 = c : C
>c2 : C2, Symbol(c2, Decl(classImplementsClass3.ts, 11, 3))
>c : C, Symbol(c, Decl(classImplementsClass3.ts, 10, 3))