==== tests/cases/compiler/optionalParamAssignmentCompat.ts (1 errors) ====
    interface I1 {
        (p1: number, p2: string): void;
    }
    interface I2 {
        p1: I1;
        m1(p1?: string): I1;
    }
    var i2: I2;
    var c: I1 = i2.p1; // should be ok
    var d: I1 = i2.m1; // should error
        ~~~~~~~~~~~~~
!!! optionalParamAssignmentCompat.ts(10,5): error TS2012: Cannot convert '(p1?: string) => I1' to 'I1':
!!! 	Call signatures of types '(p1?: string) => I1' and 'I1' are incompatible.
    