inference: permit non-direct recursion reducers (#50696)

Fix #45759
Fix #46557
Fix #31485

Depends on #50694 due to a failing broadcast test without it (related to
#50695)

base/compiler/abstractinterpretation.jl

@@ -543,25 +543,30 @@ function abstract_call_method(interp::AbstractInterpreter,
     if topmost !== nothing
         msig = unwrap_unionall(method.sig)::DataType
         spec_len = length(msig.parameters) + 1
-        ls = length(sigtuple.parameters)
         mi = frame_instance(sv)
 
+        if isdefined(method, :recursion_relation)
+            # We don't require the recursion_relation to be transitive, so
+            # apply a hard limit
+            hardlimit = true
+        end
+
         if method === mi.def
             # Under direct self-recursion, permit much greater use of reducers.
             # here we assume that complexity(specTypes) :>= complexity(sig)
             comparison = mi.specTypes
             l_comparison = length((unwrap_unionall(comparison)::DataType).parameters)
             spec_len = max(spec_len, l_comparison)
+        elseif !hardlimit && isa(topmost, InferenceState)
+            # Without a hardlimit, permit use of reducers too.
+            comparison = frame_instance(topmost).specTypes
+            # n.b. currently don't allow vararg reducers
+            #l_comparison = length((unwrap_unionall(comparison)::DataType).parameters)
+            #spec_len = max(spec_len, l_comparison)
         else
             comparison = method.sig
         end
 
-        if isdefined(method, :recursion_relation)
-            # We don't require the recursion_relation to be transitive, so
-            # apply a hard limit
-            hardlimit = true
-        end
-
         # see if the type is actually too big (relative to the caller), and limit it if required
         newsig = limit_type_size(sig, comparison, hardlimit ? comparison : mi.specTypes, InferenceParams(interp).tuple_complexity_limit_depth, spec_len)
 
@@ -588,6 +593,7 @@ function abstract_call_method(interp::AbstractInterpreter,
                     poison_callstack!(sv, parentframe === nothing ? topmost : parentframe)
                 end
             end
+            # n.b. this heuristic depends on the non-local state, so we must record the limit later
             sig = newsig
             sparams = svec()
             edgelimited = true

test/compiler/inference.jl

@@ -5100,6 +5100,34 @@ end
 end |> only === String
 # JET.test_call(s::AbstractString->Base._string(s, 'c'))
 
+# issue #45759 #46557
+g45759(x::Tuple{Any,Vararg}) = x[1] + _g45759(x[2:end])
+g45759(x::Tuple{}) = 0
+_g45759(x) = g45759(x)
+@test only(Base.return_types(g45759, Tuple{Tuple{Int,Int,Int,Int,Int,Int,Int}})) == Int
+
+h45759(x::Tuple{Any,Vararg}; kwargs...) = x[1] + h45759(x[2:end]; kwargs...)
+h45759(x::Tuple{}; kwargs...) = 0
+@test only(Base.return_types(h45759, Tuple{Tuple{Int,Int,Int,Int,Int,Int,Int}})) == Int
+
+@test only(Base.return_types((typeof([[[1]]]),)) do x
+    sum(x) do v
+        sum(length, v)
+    end
+end) == Int
+
+struct FunctionSum{Tf}
+    functions::Tf
+end
+(F::FunctionSum)(x) = sum(f -> f(x), F.functions)
+F = FunctionSum((x -> sqrt(x), FunctionSum((x -> x^2, x -> x^3))))
+@test @inferred(F(1.)) === 3.0
+
+f31485(arr::AbstractArray{T, 0}) where {T} = arr
+indirect31485(arr) = f31485(arr)
+f31485(arr::AbstractArray{T, N}) where {T, N} = indirect31485(view(arr, 1, ntuple(i -> :, Val(N-1))...))
+@test @inferred(f31485(zeros(3,3,3,3,3),)) == fill(0.0)
+
 # override const-prop' return type with the concrete-eval result
 # if concrete-eval returns non-inlineable constant
 Base.@assume_effects :foldable function continue_const_prop(i, j)