diff options
| -rw-r--r-- | driver/parser.go | 3 | ||||
| -rw-r--r-- | driver/parser_test.go | 44 |
2 files changed, 47 insertions, 0 deletions
diff --git a/driver/parser.go b/driver/parser.go index 7b6df7b..fa89fcf 100644 --- a/driver/parser.go +++ b/driver/parser.go @@ -121,8 +121,11 @@ func (p *Parser) Parse() error { } // semantic action + prodNum := act lhs := p.gram.ParsingTable.LHSSymbols[prodNum] + + // When an alternative is empty, `n` will be 0, and `handle` will be empty slice. n := p.gram.ParsingTable.AlternativeSymbolCounts[prodNum] handle := p.semStack[len(p.semStack)-n:] diff --git a/driver/parser_test.go b/driver/parser_test.go index 8713893..3dec508 100644 --- a/driver/parser_test.go +++ b/driver/parser_test.go @@ -104,6 +104,50 @@ id: "[A-Za-z_][0-9A-Za-z_]*"; ), ), }, + // The driver can reduce productions that have the empty alternative and can generate a CST (and AST) node. + { + specSrc: ` +s + : foo bar + ; +foo + : + ; +bar + : bar_text + | + ; +bar_text: "bar"; +`, + src: ``, + cst: nonTermNode("s", + termNode("foo", ""), + termNode("bar", ""), + ), + }, + // The driver can reduce productions that have the empty alternative and can generate a CST (and AST) node. + { + specSrc: ` +s + : foo bar + ; +foo + : + ; +bar + : bar_text + | + ; +bar_text: "bar"; +`, + src: `bar`, + cst: nonTermNode("s", + termNode("foo", ""), + nonTermNode("bar", + termNode("bar_text", "bar"), + ), + ), + }, { specSrc: ` mode_tran_seq |