[WIP] add error_squiggle gem

```
$ ./local/bin/ruby -e '1.time {}'
-e:1:in `<main>': undefined method `time' for 1:Integer (NoMethodError)

1.time {}
 ^^^^^
Did you mean?  times
```

https://bugs.ruby-lang.org/issues/17930

1 files changed, 6 insertions, 0 deletions

diff --git a/ruby.c b/ruby.c
index baa2f251c2..c8b3964c39 100644
--- a/ruby.c
+++ b/ruby.c
@@ -94,6 +94,8 @@ void rb_warning_category_update(unsigned int mask, unsigned int bits);
 #define EACH_FEATURES(X, SEP) \
     X(gems) \
     SEP \
+    X(error_squiggle) \
+    SEP \
     X(did_you_mean) \
     SEP \
     X(rubyopt) \
@@ -320,6 +322,7 @@ usage(const char *name, int help, int highlight, int columns)
     };
     static const struct message features[] = {
 	M("gems",    "",        "rubygems (only for debugging, default: "DEFAULT_RUBYGEMS_ENABLED")"),
+	M("error_squiggle", "", "error_squiggle (default: "DEFAULT_RUBYGEMS_ENABLED")"),
 	M("did_you_mean", "",   "did_you_mean (default: "DEFAULT_RUBYGEMS_ENABLED")"),
 	M("rubyopt", "",        "RUBYOPT environment variable (default: enabled)"),
 	M("frozen-string-literal", "", "freeze all string literals (default: disabled)"),
@@ -1508,6 +1511,9 @@ ruby_opt_init(ruby_cmdline_options_t *opt)
 
     if (opt->features.set & FEATURE_BIT(gems)) {
         rb_define_module("Gem");
+        if (opt->features.set & FEATURE_BIT(error_squiggle)) {
+            rb_define_module("ErrorSquiggle");
+        }
         if (opt->features.set & FEATURE_BIT(did_you_mean)) {
             rb_define_module("DidYouMean");
         }