[laypatel13]

Problem

parseOrderExpr checks whether the word after AS is SELECT. When AS is the last word of the input, peekToken() returns a nil token with no error, so nextToken.ToString() panics.

I found this through Jaeger, which uses this parser for its SQL query tools. A query ending in ORDER BY duration AS crashed the handler instead of returning an error jaegertracing/jaeger#10134

Reproduction

parser.NewParser("SELECT * FROM t ORDER BY a AS").ParseStmts()
// panic: runtime error: invalid memory address or nil pointer dereference

Fix

Check nextToken != nil before calling ToString(). With nothing after AS, parsing continues to parseAnyKeyword(), which returns a normal error:

line 1:30 expected '<ident>', but got '<eof>'

Test

Added SELECT * FROM t ORDER BY a AS to TestParser_InvalidSyntax. It panicked before the fix and returns an error after it. make test passes.

[git-hulk]

@laypatel13 Good catch! Thank you.