Merge pull request #40832 from aviatesk/nonconditional

inference: form conditional constraint from non-`Conditional` object

base/compiler/abstractinterpretation.jl

@@ -1667,13 +1667,17 @@ function typeinf_local(interp::AbstractInterpreter, frame::InferenceState)
             elseif isa(stmt, GotoNode)
                 pc´ = (stmt::GotoNode).label
             elseif isa(stmt, GotoIfNot)
-                condt = abstract_eval_value(interp, stmt.cond, changes, frame)
+                condx = stmt.cond
+                condt = abstract_eval_value(interp, condx, changes, frame)
                 if condt === Bottom
                     empty!(frame.pclimitations)
-                end
-                if condt === Bottom
                     break
                 end
+                if !(isa(condt, Const) || isa(condt, Conditional)) && isa(condx, SlotNumber)
+                    # if this non-`Conditional` object is a slot, we form and propagate
+                    # the conditional constraint on it
+                    condt = Conditional(condx, Const(true), Const(false))
+                end
                 condval = maybe_extract_const_bool(condt)
                 l = stmt.dest::Int
                 if !isempty(frame.pclimitations)

test/compiler/inference.jl

@@ -1833,6 +1833,24 @@ end
     end == Any[Tuple{Int,Int}]
 end
 
+@testset "conditional constraint propagation from non-`Conditional` object" begin
+    @test Base.return_types((Bool,)) do b
+        if b
+            return !b ? nothing : 1 # ::Int
+        else
+            return 0
+        end
+    end == Any[Int]
+
+    @test Base.return_types((Any,)) do b
+        if b
+            return b # ::Bool
+        else
+            return nothing
+        end
+    end == Any[Union{Bool,Nothing}]
+end
+
 function f25579(g)
     h = g[]
     t = (h === nothing)