Formatter: escape backslashes in macro literals when subformatting (#…

…12582)

spec/compiler/formatter/formatter_spec.cr

@@ -2225,4 +2225,15 @@ describe Crystal::Formatter do
       break
     end
     CODE
+
+  # #12378
+  assert_format <<-CODE
+    macro foo
+      macro bar
+        \\{% begin %}
+          \\\\{% puts %}
+        \\{% end %}
+      end
+    end
+    CODE
 end

src/compiler/crystal/tools/formatter.cr

@@ -1817,7 +1817,16 @@ module Crystal
         @no_rstrip_lines.add line
       end
 
-      write @token.raw
+      raw = @token.raw
+
+      # If the macro literal has a backlash, but we are subformatting
+      # a macro, we need to escape it (if it got here unescaped it was escaped to
+      # begin with.)
+      if @subformat_nesting > 0
+        raw = raw.gsub("\\", "\\" * (@subformat_nesting + 1))
+      end
+
+      write raw
       next_macro_token
       false
     end