From 3566a9dd478f5cb6cedffbdc7628a4e976469b43 Mon Sep 17 00:00:00 2001
From: KristofferC <kcarlsson89@gmail.com>
Date: Thu, 7 Mar 2019 16:54:40 +0100
Subject: [PATCH] only do the getfield optimization when it is safe

---
 src/JuliaInterpreter.jl |  6 ++++--
 test/interpret.jl       | 18 ++++++++++++++++++
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/src/JuliaInterpreter.jl b/src/JuliaInterpreter.jl
index 74aca353417b1..4f946969e4079 100644
--- a/src/JuliaInterpreter.jl
+++ b/src/JuliaInterpreter.jl
@@ -761,8 +761,10 @@ function lookup_global_refs!(ex::Expr)
     for (i, a) in enumerate(ex.args)
         ex.head == :(=) && i == 1 && continue # Don't look up globalrefs on the LHS of an assignment (issue #98)
         if isa(a, GlobalRef)
-            r = getfield(a.mod, a.name)
-            ex.args[i] = QuoteNode(r)
+            if isdefined(a.mod, a.name) && isconst(a.mod, a.name)
+                r = getfield(a.mod, a.name)
+                ex.args[i] = QuoteNode(r)
+            end
         elseif isa(a, Expr)
             lookup_global_refs!(a)
         end
diff --git a/test/interpret.jl b/test/interpret.jl
index f2111578586af..02f5aeb2e184e 100644
--- a/test/interpret.jl
+++ b/test/interpret.jl
@@ -357,3 +357,21 @@ f113(;x) = x
     @test length(locals) == 3
     @test JuliaInterpreter.Variable(3, :x, false) in locals
 end
+
+@testset "getfield replacements" begin
+    f_gf(x) = false ? some_undef_var_zzzzzzz : x
+    @test @interpret f_gf(2) == 2
+  
+    function g_gf()
+        eval(:(z = 2))
+        return z
+    end
+    @test @interpret g_gf() == 2
+    
+    global q_gf = 0
+    function h_gf()
+        eval(:(q_gf = 2))
+        return q_gf
+    end
+    @test @interpret h_gf() == 2
+end