fix for undefined GlobalRefs (#268)

Fixes #267

Author: KristofferC

src/optimize.jl

@@ -92,15 +92,21 @@ function smallest_ref(stmts, arg, idmin)
     return idmin
 end
 
+function lookup_global_ref(a::GlobalRef)
+    if isdefined(a.mod, a.name) && isconst(a.mod, a.name)
+        r = getfield(a.mod, a.name)
+        return QuoteNode(r)
+    else
+        return a
+    end
+end
+
 function lookup_global_refs!(ex::Expr)
     (ex.head == :isdefined || ex.head == :thunk || ex.head == :toplevel) && return nothing
     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)
-            if isdefined(a.mod, a.name) && isconst(a.mod, a.name)
-                r = getfield(a.mod, a.name)
-                ex.args[i] = QuoteNode(r)
-            end
+            ex.args[i] = lookup_global_ref(a)
         elseif isa(a, Expr)
             lookup_global_refs!(a)
         end
@@ -130,7 +136,7 @@ function optimize!(code::CodeInfo, scope)
     ## Replace GlobalRefs with QuoteNodes
     for (i, stmt) in enumerate(code.code)
         if isa(stmt, GlobalRef)
-            code.code[i] = QuoteNode(getfield(stmt.mod, stmt.name))
+            code.code[i] = lookup_global_ref(stmt)
         elseif isa(stmt, Expr)
             if stmt.head == :call && stmt.args[1] == :cglobal  # cglobal requires literals
                 continue

test/interpret.jl

@@ -373,6 +373,17 @@ end
         return q_gf
     end
     @test @interpret h_gf() == 2
+
+    # https://github.com/JuliaDebug/JuliaInterpreter.jl/issues/267
+    function test_never_different(x)
+        if x < 5
+            for g in never_defined
+                print(g)
+            end
+        end
+    end
+    @test @interpret(test_never_different(10)) === nothing
+  
 end
 
 # https://github.com/JuliaDebug/JuliaInterpreter.jl/issues/130