VM: return type not taken into account when checking function type assignability

[DartBot]

This issue was originally filed by [email protected]

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see co19 test Language/10_Expressions/09_Function_Expressions_A03_t02:
typedef bool foo(int x, int y, [double a, double b]);

main() {
  foo f;
  checkTypeError( () {f = (int x, int y, [double a, double b]) => 1;});
}

According to spec Ch. 11.9, static type of a function literal includes information about static type of the return expression, so this assignment should result in a type error.

[dgrove]

Added Area-VM, Triaged labels.

[iposva-google]

Set owner to @crelier.
Added Accepted label.

[crelier]

Static types are not relevant to the VM, which only cares about actual types.

The actual return type of the function literal in this test is dynamic, according to spec ("If a function does not declare a return type explicitly, its return type is dynamic.").

So, no type error should be expected by this test or by Language/10_Expressions/09_Function_Expressions_A04_t02

I filed co19 issue #283.

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Added AsDesigned label.