Merge pull request #23470 from JuliaLang/jn/var-infer

better constant variable inference

base/inference.jl

@@ -3153,6 +3153,10 @@ function typeinf_work(frame::InferenceState)
                     # directly forward changes to an SSAValue to the applicable line
                     record_ssa_assign(changes_var.id + 1, changes.vtype.typ, frame)
                 end
+            elseif isa(stmt, NewvarNode)
+                sn = slot_id(stmt.slot)
+                changes = changes::VarTable
+                changes[sn] = VarState(Bottom, true)
             elseif isa(stmt, GotoNode)
                 pc´ = (stmt::GotoNode).label
             elseif isa(stmt, Expr)
@@ -3563,7 +3567,7 @@ function annotate_slot_load!(e::Expr, vtypes::VarTable, sv::InferenceState, unde
         elseif isa(subex, Slot)
             id = slot_id(subex)
             s = vtypes[id]
-            vt = widenconst(s.typ)
+            vt = s.typ
             if s.undef
                 # find used-undef variables
                 undefs[id] = true
@@ -3680,28 +3684,39 @@ function type_annotate!(sv::InferenceState)
 end
 
 # widen all Const elements in type annotations
-function _widen_all_consts!(e::Expr, untypedload::Vector{Bool})
+function _widen_all_consts!(e::Expr, untypedload::Vector{Bool}, slottypes::Vector{Any})
     e.typ = widenconst(e.typ)
     for i = 1:length(e.args)
         x = e.args[i]
         if isa(x, Expr)
-            _widen_all_consts!(x, untypedload)
-        elseif isa(x, Slot) && (i != 1 || e.head !== :(=))
-            untypedload[slot_id(x)] = true
+            _widen_all_consts!(x, untypedload, slottypes)
+        elseif isa(x, TypedSlot)
+            vt = widenconst(x.typ)
+            if !(vt === x.typ)
+                if slottypes[x.id] <: vt
+                    x = SlotNumber(x.id)
+                    untypedload[x.id] = true
+                else
+                    x = TypedSlot(x.id, vt)
+                end
+                e.args[i] = x
+            end
+        elseif isa(x, SlotNumber) && (i != 1 || e.head !== :(=))
+            untypedload[x.id] = true
         end
     end
     nothing
 end
+
 function widen_all_consts!(src::CodeInfo)
     for i = 1:length(src.ssavaluetypes)
         src.ssavaluetypes[i] = widenconst(src.ssavaluetypes[i])
     end
     nslots = length(src.slottypes)
     untypedload = fill(false, nslots)
-    for i = 1:length(src.code)
-        x = src.code[i]
-        isa(x, Expr) && _widen_all_consts!(x, untypedload)
-    end
+    e = Expr(:body)
+    e.args = src.code
+    _widen_all_consts!(e, untypedload, src.slottypes)
     for i = 1:nslots
         src.slottypes[i] = widen_slot_type(src.slottypes[i], untypedload[i])
     end

test/inference.jl

@@ -254,35 +254,6 @@ function foo9222()
 end
 @test 0.0 == foo9222()
 
-# make sure none of the slottypes are left as Core.Inference.Const objects
-function f18679()
-    for i = 1:2
-        if i == 1
-            a = ((),)
-        else
-            return a[1]
-        end
-    end
-end
-g18679(x::Tuple) = ()
-g18679() = g18679(any_undef_global::Union{Int,Tuple{}})
-for code in Any[
-        @code_typed(f18679())[1]
-        @code_typed(g18679())[1]]
-    @test all(x->isa(x, Type), code.slottypes)
-    local notconst(@nospecialize(other)) = true
-    notconst(slot::TypedSlot) = @test isa(slot.typ, Type)
-    function notconst(expr::Expr)
-        @test isa(expr.typ, Type)
-        for a in expr.args
-            notconst(a)
-        end
-    end
-    for e in code.code
-        notconst(e)
-    end
-end
-
 # branching based on inferrable conditions
 let f(x) = isa(x,Int) ? 1 : ""
     @test Base.return_types(f, Tuple{Int}) == [Int]
@@ -470,11 +441,62 @@ function test_inferred_static(arrow::Pair)
     end
 end
 
+function f18679()
+    local a
+    for i = 1:2
+        if i == 1
+            a = ((),)
+        else
+            return a[1]
+        end
+    end
+end
+g18679(x::Tuple) = ()
+g18679() = g18679(any_undef_global::Union{Int, Tuple{}})
+function h18679()
+    for i = 1:2
+        local a
+        if i == 1
+            a = ((),)
+        else
+            @isdefined(a) && return "BAD"
+        end
+    end
+end
+
 function g19348(x)
     a, b = x
-    return a + b
+    g = 1
+    g = 2
+    c = Base.indexed_next(x, g, g)
+    return a + b + c[1]
+end
+
+for codetype in Any[
+        @code_typed(f18679()),
+        @code_typed(g18679()),
+        @code_typed(h18679()),
+        @code_typed(g19348((1, 2.0)))]
+    # make sure none of the slottypes are left as Core.Inference.Const objects
+    code = codetype[1]
+    @test all(x->isa(x, Type), code.slottypes)
+    local notconst(@nospecialize(other)) = true
+    notconst(slot::TypedSlot) = @test isa(slot.typ, Type)
+    function notconst(expr::Expr)
+        @test isa(expr.typ, Type)
+        for a in expr.args
+            notconst(a)
+        end
+    end
+    for e in code.code
+        notconst(e)
+    end
+    test_inferred_static(code)
 end
-test_inferred_static(@code_typed g19348((1, 2.0)))
+@test f18679() === ()
+@test_throws UndefVarError(:any_undef_global) g18679()
+@test h18679() === nothing
+
 
 # issue #5575
 f5575() = zeros(Type[Float64][1], 1)