Signature matching for unbound type parameters

[MilesCranmer]

Consider the following example:

julia> specializing_typeof(::T) where {T} = T;

julia> specializing_typeof(::Type{T}) where {T} = Type{T};

julia> specializing_typeof((Type{T} where {T}).body)
ERROR: UndefVarError: `T` not defined in static parameter matching
Suggestion: run Test.detect_unbound_args to detect method arguments that do not fully constrain a type parameter.
Stacktrace:

I don't understand why it matches the second signature and hits an error, when the first signature is actually a valid match for it. For example, if I didn't have the second method, I get

julia> specializing_typeof(::T) where {T} = T;

julia> specializing_typeof((Type{T} where {T}).body)
DataType

which seems right to me.

Is this behavior expected?

(On 1.11.5; I'm assuming it is also seen in other versions)

[nsajko]

Seems like the expected behavior to me.

why it matches the second signature and hits an error, when the first signature is actually a valid match for it.

Because Type is, as a strict subtype, more specific than Any.

[nsajko]

Oh, are you saying that the call should dispatch to the first method because the method static parameter is not defined for the second method? Not sure if that's possible 🤷

[MilesCranmer]

Yes exactly