==== tests/cases/compiler/numericIndexerConstraint2.ts (1 errors) ====
    class Foo { foo() { } }
    var x: { [index: string]: Foo; };
    var a: { one: number; };
    x = a;
    ~
!!! Type '{ one: number; }' is not assignable to type '{ [x: string]: Foo; }':
!!!   Index signature is missing in type '{ one: number; }'.