Reject encodings determined at runtime as source code encodings

The encodings determined at runtime are affected by the runtime
environment, such as the OS and locale, while the file contents are
not.

1 files changed, 10 insertions, 1 deletions

diff --git a/parse.y b/parse.y
index 8eef24ebba..08bd3fb97d 100644
--- a/parse.y
+++ b/parse.y
@@ -9477,11 +9477,20 @@ parser_encode_length(struct parser_params *p, const char *name, long len)
 static void
 parser_set_encode(struct parser_params *p, const char *name)
 {
-    int idx = rb_enc_find_index(name);
     rb_encoding *enc;
     VALUE excargs[3];
 
+    const char *wrong = 0;
+    switch (*name) {
+      case 'e': case 'E': wrong = "external"; break;
+      case 'i': case 'I': wrong = "internal"; break;
+      case 'f': case 'F': wrong = "filesystem"; break;
+      case 'l': case 'L': wrong = "locale"; break;
+    }
+    if (wrong && STRCASECMP(name, wrong) == 0) goto unknown;
+    int idx = rb_enc_find_index(name);
     if (idx < 0) {
+      unknown:
         excargs[1] = rb_sprintf("unknown encoding name: %s", name);
       error:
         excargs[0] = rb_eArgError;