From 5a063ec94b5febd95bdba7c413d6c0d15c676d9a Mon Sep 17 00:00:00 2001
From: Yichao Yu <yyc1992@gmail.com>
Date: Tue, 20 Dec 2016 23:12:15 -0500
Subject: [PATCH] Handle non-const function in `return_types` special case

Fix #19641
---
 base/inference.jl | 30 +++++++++++++++++++-----------
 test/inference.jl |  6 ++++++
 2 files changed, 25 insertions(+), 11 deletions(-)

diff --git a/base/inference.jl b/base/inference.jl
index 3d22339c54396..e96008dc192af 100644
--- a/base/inference.jl
+++ b/base/inference.jl
@@ -1095,22 +1095,23 @@ function abstract_apply(af::ANY, fargs, aargtypes::Vector{Any}, vtypes::VarTable
 end
 
 function pure_eval_call(f::ANY, argtypes::ANY, atype::ANY, vtypes::VarTable, sv::InferenceState)
-    for i = 2:length(argtypes)
-        a = argtypes[i]
-        if !(isa(a,Const) || isconstType(a,false))
-            return false
-        end
-    end
-
     if f === return_type && length(argtypes) == 3
         # NOTE: only considering calls to return_type without InferenceParams arg
         tt = argtypes[3]
-        if isType(tt)
+        af = argtypes[2]
+        af_isconst = isa(af, Const) || isconstType(af, false)
+        if isconstType(tt, false) &&
+            (af_isconst || (isleaftype(af) &&
+                            !(af <: Builtin) && !(af <: IntrinsicFunction)))
             af_argtype = tt.parameters[1]
             if af_argtype <: Tuple && isa(af_argtype, DataType)
-                af = argtypes[2]
-                rt = abstract_call(isa(af,Const) ? af.val : af.parameters[1],
-                                   (), Any[argtypes[2], af_argtype.parameters...], vtypes, sv)
+                argtypes_vec = Any[af, af_argtype.parameters...]
+                if af_isconst
+                    rt = abstract_call(isa(af,Const) ? af.val : af.parameters[1],
+                                       (), argtypes_vec, vtypes, sv)
+                else
+                    rt = abstract_call_gf_by_type(nothing, argtypes_to_type(argtypes_vec), sv)
+                end
                 if isa(rt,Const)
                     return Type{widenconst(rt)}
                 elseif isleaftype(rt) || isleaftype(af_argtype) || rt === Bottom
@@ -1122,6 +1123,13 @@ function pure_eval_call(f::ANY, argtypes::ANY, atype::ANY, vtypes::VarTable, sv:
         end
     end
 
+    for i = 2:length(argtypes)
+        a = argtypes[i]
+        if !(isa(a,Const) || isconstType(a,false))
+            return false
+        end
+    end
+
     min_valid = UInt[typemin(UInt)]
     max_valid = UInt[typemax(UInt)]
     meth = _methods_by_ftype(atype, 1, sv.params.world, min_valid, max_valid)
diff --git a/test/inference.jl b/test/inference.jl
index 5c8a5f83dba8b..91d7f78b293f1 100644
--- a/test/inference.jl
+++ b/test/inference.jl
@@ -465,3 +465,9 @@ function g19348(x)
     return a + b
 end
 test_inferred_static(@code_typed g19348((1, 2.0)))
+
+# Issue 19641
+foo19641() = let a = 1.0
+    Core.Inference.return_type(x -> x + a, Tuple{Float64})
+end
+@inferred foo19641()