Syntax errors caused by unclosed {, [, ( mention specific location

Aside from a few very specific syntax errors for which detailed exceptions are
thrown, generally PHP just emits the default error messages generated by bison on syntax
error. These messages are very uninformative; they just say "Unexpected ... at line ...".

This is most problematic with constructs which can span an arbitrary number of lines, such
as blocks of code delimited by { }, 'if' conditions delimited by ( ), and so on. If a closing
delimiter is missed, the block will run for the entire remainder of the source file (which
could be thousands of lines), and then at the end, a parse error will be thrown with the
dreaded words: "Unexpected end of file".

Therefore, track the positions of opening and closing delimiters and ensure that they match
up correctly. If any mismatch or missing delimiter is detected, immediately throw a parse
error which points the user to the offending line. This is best done in the *lexer* and not
in the parser.

Thanks to Nikita Popov and George Peter Banyard for suggesting improvements.

Fixes bug #79368.
Closes GH-5364.

1 files changed, 7 insertions, 0 deletions

diff --git a/Zend/zend_language_scanner.h b/Zend/zend_language_scanner.h
index 4d51a064fc..35eccaf7e6 100644
--- a/Zend/zend_language_scanner.h
+++ b/Zend/zend_language_scanner.h
@@ -30,6 +30,7 @@ typedef struct _zend_lex_state {
 	int yy_state;
 	zend_stack state_stack;
 	zend_ptr_stack heredoc_label_stack;
+	zend_stack nest_location_stack; /* for syntax error reporting */
 
 	zend_file_handle *in;
 	uint32_t lineno;
@@ -63,6 +64,12 @@ typedef struct _zend_heredoc_label {
 	zend_bool indentation_uses_spaces;
 } zend_heredoc_label;
 
+/* Track locations of unclosed {, [, (, etc. for better syntax error reporting */
+typedef struct _zend_nest_location {
+	char text;
+	int  lineno;
+} zend_nest_location;
+
 BEGIN_EXTERN_C()
 ZEND_API void zend_save_lexical_state(zend_lex_state *lex_state);
 ZEND_API void zend_restore_lexical_state(zend_lex_state *lex_state);