MDEV-16117 SP with a single FOR statement creates but further fails to load

The code in the "sp_tail" rule in sql_yacc.yy always
used YYLIP->get_cpp_tok_start() as the start of the body,
and did not check for possible lookahead which happens
for keywords "FOR", "VALUES" and "WITH" for LALR(2)
resolution in Lex_input_stream::lex_token().

In case of the lookahead token presence,
get_tok_start_prev() should have been used instead
of get_cpp_tok_start() as the beginning of the SP body.

Change summary:

This patch hides the implementation of the lookahead
token completely inside Lex_input_stream.
The users of Lex_input_stream now just get token-by-token
transparently and should not care about lookahead any more.
Now external users of Lex_input_stream
are not aware of the lookahead token at all.

Change details:

- Moving Lex_input_stream::has_lookahead() into the "private" section.

- Removing Lex_input_stream::get_tok_start_prev() and
  Lex_input_stream::get_cpp_start_prev().

- Fixing the external code to call get_tok_start() and get_cpp_tok_start()
  in all places where get_tok_start_prev() and get_cpp_start_prev()
  where used.

- Adding a test for has_lookahead() right inside
  get_tok_start() and get_cpp_tok_start().
  If there is a lookahead token, these methods now
  return the position of the previous token automatically:

   const char *get_tok_start()
   {
     return has_lookahead() ? m_tok_start_prev : m_tok_start;
   }

   const char *get_cpp_tok_start()
   {
    return has_lookahead() ? m_cpp_tok_start_prev : m_cpp_tok_start;
   }

- Fixing the internal code inside Lex_input_stream methods
  to use m_tok_start and m_cpp_tok_start directly,
  instead of calling get_tok_start() and get_cpp_tok_start(),
  to make sure to access to the *current* token position
  (independently of a lookahead token presence).

1 files changed, 4 insertions, 16 deletions

diff --git a/sql/sql_lex.h b/sql/sql_lex.h
index 43478c60146..9e476f3a5eb 100644
--- a/sql/sql_lex.h
+++ b/sql/sql_lex.h
@@ -2331,8 +2331,6 @@ private:
     return (uint) ((m_ptr - m_tok_start) - 1);
   }
 
-public:
-
   /**
     Test if a lookahead token was already scanned by lex_token(),
     for LALR(2) resolution.
@@ -2342,6 +2340,8 @@ public:
     return lookahead_token >= 0;
   }
 
+public:
+
   /**
     End of file indicator for the query text to parse.
     @return true if there are no more characters to parse
@@ -2372,7 +2372,7 @@ public:
   /** Get the token start position, in the raw buffer. */
   const char *get_tok_start()
   {
-    return m_tok_start;
+    return has_lookahead() ? m_tok_start_prev : m_tok_start;
   }
 
   void set_cpp_tok_start(const char *pos)
@@ -2386,28 +2386,16 @@ public:
     return m_tok_end;
   }
 
-  /** Get the previous token start position, in the raw buffer. */
-  const char *get_tok_start_prev()
-  {
-    return m_tok_start_prev;
-  }
-
   /** Get the current stream pointer, in the raw buffer. */
   const char *get_ptr()
   {
     return m_ptr;
   }
 
-  /** Get the previus token start position, in the pre-processed buffer. */
-  const char *get_cpp_start_prev()
-  {
-    return m_cpp_tok_start_prev;
-  }
-
   /** Get the token start position, in the pre-processed buffer. */
   const char *get_cpp_tok_start()
   {
-    return m_cpp_tok_start;
+    return has_lookahead() ? m_cpp_tok_start_prev : m_cpp_tok_start;
   }
 
   /** Get the token end position, in the pre-processed buffer. */