ICE 99999 when upcasting existential from derived interface to base interface

[jvepsalainen-nv]

Upcasting an interface-typed (existential) value from a derived interface to a base interface causes an internal compiler error (ICE 99999) with the message "Unexpected context type for parameter info retrieval".

This affects both generic and non-generic interface hierarchies.

Reproduction (non-generic):

interface IBase
{
    float getValue();
}

interface IDerived : IBase
{
    float transform(float input);
}

struct Impl : IDerived
{
    float v;
    float getValue() { return v; }
    float transform(float input) { return input + v; }
}

void test()
{
    IDerived derived;
    derived = Impl(10.0);

    // This upcast triggers ICE 99999
    IBase base = derived;
    float x = base.getValue();
}

Reproduction (generic):

interface IBase<T : IArithmetic>
{
    T getValue();
}

interface IDerived<T : IArithmetic> : IBase<T>
{
    T transform(T input);
}

struct Impl : IDerived<float>
{
    float v;
    float getValue() { return v; }
    float transform(float input) { return input + v; }
}

void test()
{
    IDerived<float> derived;
    derived = Impl(10.0);

    // This upcast also triggers ICE 99999
    IBase<float> base = derived;
    float x = base.getValue();
}

Note: Using IDerived directly (without upcasting to IBase) works correctly with dynamic dispatch. The ICE occurs specifically when assigning the existential to the base interface type.