Fix error messages for unterminated ( and {

src/prism.c

@@ -476,7 +476,13 @@ pm_parser_err_token(pm_parser_t *parser, const pm_token_t *token, pm_diagnostic_
  * given token and a format string.
  */
 #define PM_PARSER_ERR_TOKEN_FORMAT(parser, token, diag_id, ...) \
-    PM_PARSER_ERR_FORMAT(parser, (token).start, (token).end, diag_id, __VA_ARGS__)
+    do { \
+        pm_token_t errtok = (token); \
+        if (errtok.type == PM_TOKEN_EOF && errtok.start > parser->start && (*(errtok.start - 1) == '\n')) { \
+            errtok.start = errtok.start - 1; \
+        } \
+        PM_PARSER_ERR_FORMAT(parser, (token).start, (token).end, diag_id, __VA_ARGS__); \
+    } while(0)
 
 /**
  * Append an error to the list of errors on the parser using the location of the

test/prism/errors/unterminated_block.txt

@@ -0,0 +1,4 @@
+foo {
+     ^ unexpected end-of-input, assuming it is closing the parent top level context
+     ^ expected a block beginning with `{` to end with `}`
+

test/prism/errors/unterminated_method_parameters.txt

@@ -0,0 +1,3 @@
+foo(
+    ^ unexpected end-of-input; expected a `)` to close the arguments
+