Clone macro default argument before macro expansion

makenowjust · asterite · commit 157eca015afb · 2018-01-10T11:40:41.000-03:00
diff --git a/spec/compiler/semantic/macro_spec.cr b/spec/compiler/semantic/macro_spec.cr
@@ -1223,4 +1223,19 @@ describe "Semantic: macro" do
       Foo.new.foo
     )) { int32 }
   end
+
+  it "clones default value before expanding" do
+    assert_type(%(
+      FOO = {} of String => String?
+
+      macro foo(x = {} of String => String)
+        {% FOO["foo"] = x["foo"] %}
+        {% x["foo"] = "foo" %}
+      end
+
+      foo
+      foo
+      {{ FOO["foo"] }}
+    )) { nil_type }
+  end
 end
diff --git a/src/compiler/crystal/macros/interpreter.cr b/src/compiler/crystal/macros/interpreter.cr
@@ -51,7 +51,7 @@ module Crystal
         next if vars.has_key?(macro_arg.name)
 
         default_value = default_value.expand_node(call.location, call.end_location) if default_value.is_a?(MagicConstant)
-        vars[macro_arg.name] = default_value
+        vars[macro_arg.name] = default_value.clone
       end
 
       # The named arguments
