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inference: permit recursive type traits (#50694)
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We had a special case for Type that disallowed type trait recursion in
favor of a pattern that almost never appears in code (only once in the
compiler by accident where it doesn't matter). This was unnecessarily
confusing and unexpected to predict what can infer, and made traits
harder than necessary (such as Broadcast.ndims since 70fc3cd).

Fix #43296
Fix #43368
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@vtjnash
vtjnash committed Aug 2, 2023
1 parent 3708229 commit 33e3d9f
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Showing 2 changed files with 71 additions and 24 deletions.
45 changes: 26 additions & 19 deletions base/compiler/typelimits.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -116,15 +116,32 @@ function _limit_type_size(@nospecialize(t), @nospecialize(c), sources::SimpleVec
return Union{a, b}
end
elseif isa(t, DataType)
if isType(t) # see equivalent case in type_more_complex
tt = unwrap_unionall(t.parameters[1])
if isa(tt, Union) || isa(tt, TypeVar) || isType(tt)
is_derived_type_from_any(tt, sources, depth + 1) && return t
if isType(t)
# Type is fairly important, so do not widen it as fast as other types if avoidable
tt = t.parameters[1]
ttu = unwrap_unionall(tt) # TODO: use argument_datatype(tt) after #50692 fixed
# must forbid nesting through this if we detect that potentially occurring
# we already know !is_derived_type_from_any so refuse to recurse here
if !isa(ttu, DataType)
return Type
elseif isType(ttu)
return Type{<:Type}
end
# try to peek into c to get a comparison object, but if we can't perhaps t is already simple enough on its own
# (this is slightly more permissive than type_more_complex implements for the same case).
if isType(c)
ct = c.parameters[1]
else
isType(c) && (c = unwrap_unionall(c.parameters[1]))
type_more_complex(tt, c, sources, depth, 0, 0) || return t
ct = Union{}
end
return Type
Qt = __limit_type_size(tt, ct, sources, depth + 1, 0)
Qt === Any && return Type
Qt === tt && return t
# Can't form Type{<:Qt} just yet, without first make sure we limited the depth
# enough, since this moves Qt outside of Type for is_derived_type_from_any
Qt = __limit_type_size(tt, ct, sources, depth + 2, 0)
Qt === Any && return Type
return Type{<:Qt}
elseif isa(c, DataType)
tP = t.parameters
cP = c.parameters
Expand Down Expand Up @@ -157,6 +174,7 @@ function _limit_type_size(@nospecialize(t), @nospecialize(c), sources::SimpleVec
end
end
if allowed_tuplelen < 1 && t.name === Tuple.name
# forbid nesting Tuple{Tuple{Tuple...}} through this
return Any
end
widert = t.name.wrapper
Expand Down Expand Up @@ -247,18 +265,7 @@ function type_more_complex(@nospecialize(t), @nospecialize(c), sources::SimpleVe
# base case for data types
if isa(t, DataType)
tP = t.parameters
if isType(t)
# Treat Type{T} and T as equivalent to allow taking typeof any
# source type (DataType) anywhere as Type{...}, as long as it isn't
# nesting as Type{Type{...}}
tt = unwrap_unionall(t.parameters[1])
if isa(tt, Union) || isa(tt, TypeVar) || isType(tt)
return !is_derived_type_from_any(tt, sources, depth + 1)
else
isType(c) && (c = unwrap_unionall(c.parameters[1]))
return type_more_complex(tt, c, sources, depth, 0, 0)
end
elseif isa(c, DataType) && t.name === c.name
if isa(c, DataType) && t.name === c.name
cP = c.parameters
length(cP) < length(tP) && return true
isempty(tP) && return false
Expand Down
50 changes: 45 additions & 5 deletions test/compiler/inference.jl
View file
Original file line number Diff line number Diff line change
Expand Up @@ -60,7 +60,8 @@ end
# issue #42835
@test !Core.Compiler.type_more_complex(Int, Any, Core.svec(), 1, 1, 1)
@test !Core.Compiler.type_more_complex(Int, Type{Int}, Core.svec(), 1, 1, 1)
@test !Core.Compiler.type_more_complex(Type{Int}, Any, Core.svec(), 1, 1, 1)
@test Core.Compiler.type_more_complex(Type{Int}, Any, Core.svec(), 1, 1, 1) # maybe should be fixed?
@test Core.Compiler.limit_type_size(Type{Int}, Any, Union{}, 0, 0) == Type{Int}
@test Core.Compiler.type_more_complex(Type{Type{Int}}, Type{Int}, Core.svec(Type{Int}), 1, 1, 1)
@test Core.Compiler.type_more_complex(Type{Type{Int}}, Int, Core.svec(Type{Int}), 1, 1, 1)
@test Core.Compiler.type_more_complex(Type{Type{Int}}, Any, Core.svec(), 1, 1, 1)
Expand All @@ -71,22 +72,23 @@ end
@test Core.Compiler.type_more_complex(ComplexF32, Type{ComplexF32}, Core.svec(), 1, 1, 1)
@test !Core.Compiler.type_more_complex(Type{ComplexF32}, Any, Core.svec(Type{Type{ComplexF32}}), 1, 1, 1)
@test Core.Compiler.type_more_complex(Type{ComplexF32}, Type{Type{ComplexF32}}, Core.svec(), 1, 1, 1)
@test !Core.Compiler.type_more_complex(Type{ComplexF32}, ComplexF32, Core.svec(), 1, 1, 1)
@test Core.Compiler.type_more_complex(Type{ComplexF32}, ComplexF32, Core.svec(), 1, 1, 1)
@test Core.Compiler.limit_type_size(Type{ComplexF32}, ComplexF32, Union{}, 1, 1) == Type{<:Complex}
@test Core.Compiler.type_more_complex(Type{ComplexF32}, Any, Core.svec(), 1, 1, 1)
@test Core.Compiler.type_more_complex(Type{Type{ComplexF32}}, Type{ComplexF32}, Core.svec(Type{ComplexF32}), 1, 1, 1)
@test Core.Compiler.type_more_complex(Type{Type{ComplexF32}}, ComplexF32, Core.svec(ComplexF32), 1, 1, 1)
@test Core.Compiler.type_more_complex(Type{Type{Type{ComplexF32}}}, Type{Type{ComplexF32}}, Core.svec(Type{ComplexF32}), 1, 1, 1)

# n.b. Type{Type{Union{}} === Type{Core.TypeofBottom}
@test !Core.Compiler.type_more_complex(Type{Union{}}, Any, Core.svec(), 1, 1, 1)
@test !Core.Compiler.type_more_complex(Type{Type{Union{}}}, Any, Core.svec(), 1, 1, 1)
@test Core.Compiler.type_more_complex(Type{Union{}}, Any, Core.svec(), 1, 1, 1)
@test Core.Compiler.type_more_complex(Type{Type{Union{}}}, Any, Core.svec(), 1, 1, 1)
@test Core.Compiler.type_more_complex(Type{Type{Type{Union{}}}}, Any, Core.svec(), 1, 1, 1)
@test Core.Compiler.type_more_complex(Type{Type{Type{Union{}}}}, Type{Type{Union{}}}, Core.svec(Type{Type{Union{}}}), 1, 1, 1)
@test Core.Compiler.type_more_complex(Type{Type{Type{Type{Union{}}}}}, Type{Type{Type{Union{}}}}, Core.svec(Type{Type{Type{Union{}}}}), 1, 1, 1)

@test !Core.Compiler.type_more_complex(Type{1}, Type{2}, Core.svec(), 1, 1, 1)
@test Core.Compiler.type_more_complex(Type{Union{Float32,Float64}}, Union{Float32,Float64}, Core.svec(Union{Float32,Float64}), 1, 1, 1)
@test !Core.Compiler.type_more_complex(Type{Union{Float32,Float64}}, Union{Float32,Float64}, Core.svec(Union{Float32,Float64}), 0, 1, 1)
@test Core.Compiler.type_more_complex(Type{Union{Float32,Float64}}, Union{Float32,Float64}, Core.svec(Union{Float32,Float64}), 0, 1, 1)
@test Core.Compiler.type_more_complex(Type{<:Union{Float32,Float64}}, Type{Union{Float32,Float64}}, Core.svec(Union{Float32,Float64}), 1, 1, 1)
@test Core.Compiler.type_more_complex(Type{<:Union{Float32,Float64}}, Any, Core.svec(Union{Float32,Float64}), 1, 1, 1)

Expand All @@ -101,6 +103,44 @@ let # 40336
@test t !== r && t <: r
end

@test Core.Compiler.limit_type_size(Type{Type{Type{Int}}}, Type, Union{}, 0, 0) == Type{<:Type}
@test Core.Compiler.limit_type_size(Type{Type{Int}}, Type, Union{}, 0, 0) == Type{<:Type}
@test Core.Compiler.limit_type_size(Type{Int}, Type, Union{}, 0, 0) == Type{Int}
@test Core.Compiler.limit_type_size(Type{<:Int}, Type, Union{}, 0, 0) == Type{<:Int}
@test Core.Compiler.limit_type_size(Type{ComplexF32}, ComplexF32, Union{}, 0, 0) == Type{<:Complex} # added nesting
@test Core.Compiler.limit_type_size(Type{ComplexF32}, Type{ComplexF64}, Union{}, 0, 0) == Type{ComplexF32} # base matches
@test Core.Compiler.limit_type_size(Type{ComplexF32}, Type, Union{}, 0, 0) == Type{<:Complex}
@test_broken Core.Compiler.limit_type_size(Type{<:ComplexF64}, Type, Union{}, 0, 0) == Type{<:Complex}
@test Core.Compiler.limit_type_size(Type{<:ComplexF64}, Type, Union{}, 0, 0) == Type #50692
@test Core.Compiler.limit_type_size(Type{Union{ComplexF32,ComplexF64}}, Type, Union{}, 0, 0) == Type
@test_broken Core.Compiler.limit_type_size(Type{Union{ComplexF32,ComplexF64}}, Type, Union{}, 0, 0) == Type{<:Complex} #50692
@test Core.Compiler.limit_type_size(Type{Union{Float32,Float64}}, Type, Union{}, 0, 0) == Type
@test Core.Compiler.limit_type_size(Type{Union{Int,Type{Int}}}, Type{Type{Int}}, Union{}, 0, 0) == Type
@test Core.Compiler.limit_type_size(Type{Union{Int,Type{Int}}}, Union{Type{Int},Type{Type{Int}}}, Union{}, 0, 0) == Type
@test Core.Compiler.limit_type_size(Type{Union{Int,Type{Int}}}, Type{Union{Type{Int},Type{Type{Int}}}}, Union{}, 0, 0) == Type{Union{Int, Type{Int}}}
@test Core.Compiler.limit_type_size(Type{Union{Int,Type{Int}}}, Type{Type{Int}}, Union{}, 0, 0) == Type


# issue #43296 #43296
struct C43296{t,I} end
r43296(b) = r43296(typeof(b))
r43296(::Type) = nothing
r43296(::Nothing) = nonexistent
r43296(::Type{C43296{c,d}}) where {c,d} = f43296(r43296(c), e)
f43296(::Nothing, :) = nothing
f43296(g, :) = h
k43296(b, j, :) = l
k43296(b, j, ::Nothing) = b
i43296(b, j) = k43296(b, j, r43296(j))
@test only(Base.return_types(i43296, (Int, C43296{C43296{C43296{Val, Tuple}, Tuple}}))) == Int

abstract type e43296{a, j} <: AbstractArray{a, j} end
abstract type b43296{a, j, c, d} <: e43296{a, j} end
struct h43296{a, j, f, d, i} <: b43296{a, j, f, d} end
Base.ndims(::Type{f}) where {f<:e43296} = ndims(supertype(f))
Base.ndims(g::e43296) = ndims(typeof(g))
@test only(Base.return_types(ndims, (h43296{Any, 0, Any, Int, Any},))) == Int

@test Core.Compiler.unionlen(Union{}) == 1
@test Core.Compiler.unionlen(Int8) == 1
@test Core.Compiler.unionlen(Union{Int8, Int16}) == 2
Expand Down

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