Compiler: remove hasuniquerep (unsound predicate)
Remove hasuniquerep, which incorrectly claimed T == S implies T === S
for concrete types. This was always unsound: degenerate UnionAll types
like Union{T,S} where {T<:Int, S<:Int} are == to Int without being
===. ConstType was introduced to soundly recover the optimization.
Replace all hasuniquerep call sites with the semantically correct
false:
- isconstType: now only matches ConstType instances
- typeof_tfunc: Type{T} no longer returns Const(typeof(T))
- fieldtype_tfunc: field types wrapped in Type{} not Const()
- apply_type_tfunc: returns Type{ty} not Const(ty) for Type args
- tuple_tfunc: Type{T} params become Type not typeof(T)
- has_nontrivial_extended_info: Const(type_val) always has info
- isnotbrokensubtype: uses b <: a fallback instead
Update tests: where inference precision was lost due to Type{T} no
longer being treated as unique, replace Type{T} with ConstType{T} in
the test to verify that ConstType correctly recovers the precision.
Mark tests that depend on specTypes emitting ConstType as @test_broken.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
