fix hasfield for unionall-wrapped DataTypes (#36694)

Co-authored-by: Jameson Nash <vtjnash@gmail.com>

Author: JeffBezanson

base/reflection.jl

@@ -635,6 +635,8 @@ function fieldindex(T::DataType, name::Symbol, err::Bool=true)
     return Int(ccall(:jl_field_index, Cint, (Any, Any, Cint), T, name, err)+1)
 end
 
+fieldindex(t::UnionAll, name::Symbol, err::Bool=true) = fieldindex(something(argument_datatype(t)), name, err)
+
 argument_datatype(@nospecialize t) = ccall(:jl_argument_datatype, Any, (Any,), t)
 
 """

test/reflection.jl

@@ -225,6 +225,8 @@ tlayout = TLayout(5,7,11)
 @test fieldnames(TLayout) == (:x, :y, :z) == Base.propertynames(tlayout)
 @test hasfield(TLayout, :y)
 @test !hasfield(TLayout, :a)
+@test hasfield(Complex, :re)
+@test !hasfield(Complex, :qxq)
 @test hasproperty(tlayout, :x)
 @test !hasproperty(tlayout, :p)
 @test [(fieldoffset(TLayout,i), fieldname(TLayout,i), fieldtype(TLayout,i)) for i = 1:fieldcount(TLayout)] ==