more accurate lattice implementation

base/compiler/typelattice.jl

@@ -469,8 +469,13 @@ end
 @nospecializeinfer function ⊑(lattice::PartialsLattice, @nospecialize(a), @nospecialize(b))
     if isa(a, PartialStruct)
         if isa(b, PartialStruct)
-            if !(length(a.fields) == length(b.fields) && a.typ <: b.typ)
-                return false
+            a.typ <: b.typ || return false
+            if length(a.fields) ≠ length(b.fields)
+                if !(isvarargtype(a.fields[end]) || isvarargtype(b.fields[end]))
+                    length(a.fields) ≥ length(b.fields) || return false
+                else
+                    return false
+                end
             end
             for i in 1:length(b.fields)
                 af = a.fields[i]
@@ -493,8 +498,7 @@ end
         return isa(b, Type) && a.typ <: b
     elseif isa(b, PartialStruct)
         if isa(a, Const)
-            nf = nfields(a.val)
-            nf == length(b.fields) || return false
+            n_initialized(a) ≥ length(b.fields) || return false
             widea = widenconst(a)::DataType
             wideb = widenconst(b)
             wideb′ = unwrap_unionall(wideb)::DataType
@@ -504,8 +508,10 @@ end
             if wideb′.name !== Tuple.name && !(widea <: wideb)
                 return false
             end
+            nf = nfields(a.val)
             for i in 1:nf
                 isdefined(a.val, i) || continue # since ∀ T Union{} ⊑ T
+                i > length(b.fields) && break
                 bfᵢ = b.fields[i]
                 if i == nf
                     bfᵢ = unwrapva(bfᵢ)

base/compiler/typelimits.jl

@@ -321,15 +321,24 @@ end
 # even after complicated recursion and other operations on it elsewhere
 const issimpleenoughtupleelem = issimpleenoughtype
 
+function n_initialized(t::Const)
+    nf = nfields(t.val)
+    return something(findfirst(i::Int->!isdefined(t.val,i), 1:nf), nf+1)-1
+end
+
 # A simplified type_more_complex query over the extended lattice
 # (assumes typeb ⊑ typea)
 @nospecializeinfer function issimplertype(𝕃::AbstractLattice, @nospecialize(typea), @nospecialize(typeb))
     @assert !isa(typea, LimitedAccuracy) && !isa(typeb, LimitedAccuracy) "LimitedAccuracy not supported by simplertype lattice" # n.b. the caller was supposed to handle these
     typea === typeb && return true
     if typea isa PartialStruct
         aty = widenconst(typea)
-        if length(typea.fields) > datatype_min_ninitialized(unwrap_unionall(aty))
-            return false # TODO more accuracy here?
+        if typeb isa Const
+            @assert length(typea.fields) ≤ n_initialized(typeb) "typeb ⊑ typea is assumed"
+        elseif typeb isa PartialStruct
+            @assert length(typea.fields) ≤ length(typeb.fields) "typeb ⊑ typea is assumed"
+        else
+            return false
         end
         for i = 1:length(typea.fields)
             ai = unwrapva(typea.fields[i])
@@ -579,26 +588,21 @@ end
     aty = widenconst(typea)
     bty = widenconst(typeb)
     if aty === bty
-        # must have egal here, since we do not create PartialStruct for non-concrete types
-        typea_nfields = nfields_tfunc(𝕃, typea)
-        typeb_nfields = nfields_tfunc(𝕃, typeb)
-        isa(typea_nfields, Const) || return nothing
-        isa(typeb_nfields, Const) || return nothing
-        type_nfields = typea_nfields.val::Int
-        type_nfields == typeb_nfields.val::Int || return nothing
-        type_nfields == 0 && return nothing
         if typea isa PartialStruct
             if typeb isa PartialStruct
-                length(typea.fields) == length(typeb.fields) || return nothing
+                nflds = min(length(typea.fields), length(typeb.fields))
             else
-                length(typea.fields) == type_nfields || return nothing
+                nflds = min(length(typea.fields), n_initialized(typeb::Const))
             end
         elseif typeb isa PartialStruct
-            length(typeb.fields) == type_nfields || return nothing
+            nflds = min(n_initialized(typea::Const), length(typeb.fields))
+        else
+            nflds = min(n_initialized(typea::Const), n_initialized(typeb::Const))
         end
-        fields = Vector{Any}(undef, type_nfields)
-        anyrefine = false
-        for i = 1:type_nfields
+        nflds == 0 && return nothing
+        fields = Vector{Any}(undef, nflds)
+        anyrefine = nflds > datatype_min_ninitialized(unwrap_unionall(aty))
+        for i = 1:nflds
             ai = getfield_tfunc(𝕃, typea, Const(i))
             bi = getfield_tfunc(𝕃, typeb, Const(i))
             # N.B.: We're assuming here that !isType(aty), because that case

test/compiler/inference.jl

@@ -4754,6 +4754,14 @@ end
         @test a ⊑ c && b ⊑ c
         @test c === typeof(init)
     end
+    let init = Base.ImmutableDict{Any,Any}(1,2)
+        a = Const(init)
+        b = PartialStruct(typeof(init), Any[Const(getfield(init,1)), Any, Any])
+        c = a ⊔ b
+        @test a ⊑ c && b ⊑ c
+        @test c isa PartialStruct
+        @test length(c.fields) == 3
+    end
     let init = Base.ImmutableDict{Number,Number}()
         a = Const(init)
         b = PartialStruct(typeof(init), Any[Const(init), Number, ComplexF64])
@@ -4766,6 +4774,7 @@ end
         b = PartialStruct(typeof(init), Any[Const(init), Number, ComplexF64])
         c = a ⊔ b
         @test a ⊑ c && b ⊑ c
+        @test c isa PartialStruct
         @test c.fields[2] === Number
         @test c.fields[3] === ComplexF64
     end
@@ -4774,9 +4783,40 @@ end
         b = PartialStruct(typeof(init), Any[Const(init), ComplexF32, Union{ComplexF32,ComplexF64}])
         c = a ⊔ b
         @test a ⊑ c && b ⊑ c
+        @test c isa PartialStruct
         @test c.fields[2] === Complex
         @test c.fields[3] === Complex
     end
+    let T = Base.ImmutableDict{Number,Number}
+        a = PartialStruct(T, Any[T])
+        b = PartialStruct(T, Any[T, Number, Number])
+        @test b ⊑ a
+        c = a ⊔ b
+        @test a ⊑ c && b ⊑ c
+        @test c isa PartialStruct
+        @test length(c.fields) == 1
+    end
+    let T = Base.ImmutableDict{Number,Number}
+        a = PartialStruct(T, Any[T])
+        b = Const(T())
+        c = a ⊔ b
+        @test a ⊑ c && b ⊑ c
+        @test c === T
+    end
+    let T = Base.ImmutableDict{Number,Number}
+        a = Const(T())
+        b = PartialStruct(T, Any[T])
+        c = a ⊔ b
+        @test a ⊑ c && b ⊑ c
+        @test c === T
+    end
+    let T = Base.ImmutableDict{Number,Number}
+        a = Const(T())
+        b = Const(T(1,2))
+        c = a ⊔ b
+        @test a ⊑ c && b ⊑ c
+        @test c === T
+    end
 
     global const ginit43784 = Base.ImmutableDict{Any,Any}()
     @test Base.return_types() do