Change macro var location to var node

spec/compiler/macro/macro_expander_spec.cr

@@ -163,7 +163,7 @@ describe "MacroExpander" do
     assert_macro %({{node}}), "42", {node: node}, expected_pragmas: {
       0 => [
         Lexer::LocPushPragma.new,
-        Lexer::LocSetPragma.new("foo.cr", 10, 20),
+        Lexer::LocSetPragma.new("", 1, 19),
       ] of Lexer::LocPragma,
       2 => [
         Lexer::LocPopPragma.new,

src/compiler/crystal/macros/interpreter.cr

@@ -133,10 +133,7 @@ module Crystal
     end
 
     def visit(node : Var)
-      var = @vars[node.name]?
-      if var
-        return @last = var
-      end
+      value = @vars[node.name]?
 
       # Try to consider the var as a top-level macro call.
       #
@@ -149,11 +146,15 @@ module Crystal
       #
       # and in this case the parser has no idea about this, so the only
       # solution is to do it now.
-      if value = interpret_top_level_call?(Call.new(nil, node.name))
-        return @last = value
+      value ||= interpret_top_level_call?(Call.new(nil, node.name))
+
+      unless value
+        node.raise "undefined macro variable '#{node.name}'"
       end
 
-      node.raise "undefined macro variable '#{node.name}'"
+      # locate the value at the place where the variable is referenced
+      value = value.dup.at(node)
+      @last = value
     end
 
     def visit(node : StringInterpolation)