Method dispatch bug involving tuple types

[simonster]

typealias TupleType{T<:Tuple} Type{T};
f(::Any) = (while false; end; nothing);
f(T::TupleType) = (while false; end; @assert isa(T, TupleType));
g(x) = f(typeof(x));
g((1, 2)) # works if this line is removed
g(UInt8)

The last line yields:

ERROR: AssertionError: isa(T,TupleType)

Tested with 54e9ed1