another improvement to static parameter precision (#31001)

base/compiler/inferencestate.jl

@@ -136,43 +136,49 @@ function sptypes_from_meth_instance(linfo::MethodInstance)
  for i = 1:length(sp)
  v = sp[i]
  if v isa TypeVar
- ub = v.ub
- while ub isa TypeVar
- ub = ub.ub
+ fromArg = 0
+ # if this parameter came from arg::Type{T}, then `arg` is more precise than
+ # Type{T} where lb<:T<:ub
+ sig = linfo.def.sig
+ temp = sig
+ for j = 1:i-1
+ temp = temp.body
  end
- if has_free_typevars(ub)
- ub = Any
+ Pi = temp.var
+ while temp isa UnionAll
+ temp = temp.body
  end
- lb = v.lb
- while lb isa TypeVar
- lb = lb.lb
- end
- if has_free_typevars(lb)
- lb = Bottom
+ sigtypes = temp.parameters
+ for j = 1:length(sigtypes)
+ tj = sigtypes[j]
+ if isType(tj) && tj.parameters[1] === Pi
+ fromArg = j
+ break
+ end
  end
- if Any <: ub && lb <: Bottom
- ty = Any
- # if this parameter came from arg::Type{T}, we know that T::Type
- sig = linfo.def.sig
- temp = sig
- for j = 1:i-1
- temp = temp.body
+ if fromArg > 0
+ ty = fieldtype(linfo.specTypes, fromArg)
+ else
+ ub = v.ub
+ while ub isa TypeVar
+ ub = ub.ub
  end
- Pi = temp.var
- while temp isa UnionAll
- temp = temp.body
+ if has_free_typevars(ub)
+ ub = Any
  end
- sigtypes = temp.parameters
- for j = 1:length(sigtypes)
- tj = sigtypes[j]
- if isType(tj) && tj.parameters[1] === Pi
- ty = Type
- break
- end
+ lb = v.lb
+ while lb isa TypeVar
+ lb = lb.lb
+ end
+ if has_free_typevars(lb)
+ lb = Bottom
+ end
+ if Any <: ub && lb <: Bottom
+ ty = Any
+ else
+ tv = TypeVar(v.name, lb, ub)
+ ty = UnionAll(tv, Type{tv})
  end
- else
- tv = TypeVar(v.name, lb, ub)
- ty = UnionAll(tv, Type{tv})
  end
  else
  ty = Const(v)

test/compiler/inference.jl

@@ -2216,3 +2216,4 @@ _call_rttf_test() = Core.Compiler.return_type(_rttf_test, Tuple{Any})
 
 f_with_Type_arg(::Type{T}) where {T} = T
 @test Base.return_types(f_with_Type_arg, (Any,)) == Any[Type]
+@test Base.return_types(f_with_Type_arg, (Type{Vector{T}} where T,)) == Any[Type{Vector{T}} where T]