diff options
Diffstat (limited to 'grammar/grammar.go')
| -rw-r--r-- | grammar/grammar.go | 21 |
1 files changed, 20 insertions, 1 deletions
diff --git a/grammar/grammar.go b/grammar/grammar.go index b405429..4e5b3b2 100644 --- a/grammar/grammar.go +++ b/grammar/grammar.go @@ -701,6 +701,7 @@ func (b *GrammarBuilder) genProductionsAndActions(root *spec.RootNode, symTabAnd for _, alt := range prod.RHS { altSyms := make([]symbol, len(alt.Elements)) offsets := map[string]int{} + ambiguousIDOffsets := map[string]struct{}{} for i, elem := range alt.Elements { var sym symbol if elem.Pattern != "" { @@ -756,7 +757,15 @@ func (b *GrammarBuilder) genProductionsAndActions(root *spec.RootNode, symTabAnd // A symbol having a label can be specified by both the label and the symbol name. // So record the symbol's position, whether or not it has a label. if elem.ID != "" { - offsets[elem.ID] = i + if _, exist := offsets[elem.ID]; exist { + // When the same symbol appears multiple times in an alternative, the symbol is ambiguous. When we need + // to specify the symbol in a directive, we cannot use the name of the ambiguous symbol. Instead, specify + // a label to resolve the ambiguity. + delete(offsets, elem.ID) + ambiguousIDOffsets[elem.ID] = struct{}{} + } else { + offsets[elem.ID] = i + } } } @@ -842,6 +851,16 @@ func (b *GrammarBuilder) genProductionsAndActions(root *spec.RootNode, symTabAnd continue LOOP_RHS } + if _, ambiguous := ambiguousIDOffsets[param.ID]; ambiguous { + b.errs = append(b.errs, &verr.SpecError{ + Cause: semErrAmbiguousElem, + Detail: fmt.Sprintf("'%v' is ambiguous", param.ID), + Row: param.Pos.Row, + Col: param.Pos.Col, + }) + continue LOOP_RHS + } + offset, ok := offsets[param.ID] if !ok { b.errs = append(b.errs, &verr.SpecError{ |