fix: Fixes for #3718

  o Implement collections with generics to solve hash collisions
  o Fix type casting in LL start parser simulation optimization
  o General minor tidy ups

Acknowledgements to @kaby76 for help with tracing errors

Signed-off-by: Jim.Idle <jimi@gatherstars.com>

runtime/Go/antlr/atn_config.go

@@ -20,6 +20,8 @@ type comparable interface {
 type ATNConfig interface {
 	comparable
 
+	gequals(other Collectable[ATNConfig]) bool
+
 	hash() int
 
 	GetState() ATNState
@@ -47,7 +49,7 @@ type BaseATNConfig struct {
 	reachesIntoOuterContext    int
 }
 
-func NewBaseATNConfig7(old *BaseATNConfig) *BaseATNConfig { // TODO: Dup
+func NewBaseATNConfig7(old *BaseATNConfig) ATNConfig { // TODO: Dup
 	return &BaseATNConfig{
 		state:                   old.state,
 		alt:                     old.alt,
@@ -134,10 +136,13 @@ func (b *BaseATNConfig) GetReachesIntoOuterContext() int {
 func (b *BaseATNConfig) SetReachesIntoOuterContext(v int) {
 	b.reachesIntoOuterContext = v
 }
+func (b *BaseATNConfig) equals(o interface{}) bool {
+	return b.gequals(o.(Collectable[ATNConfig]))
+}
 
 // An ATN configuration is equal to another if both have the same state, they
 // predict the same alternative, and syntactic/semantic contexts are the same.
-func (b *BaseATNConfig) equals(o interface{}) bool {
+func (b *BaseATNConfig) gequals(o Collectable[ATNConfig]) bool {
 	if b == o {
 		return true
 	}
@@ -153,7 +158,7 @@ func (b *BaseATNConfig) equals(o interface{}) bool {
 	if b.context == nil {
 		equal = other.context == nil
 	} else {
-		equal = b.context.equals(other.context)
+		equal = b.context.gequals(other.context)
 	}
 
 	var (
@@ -262,6 +267,10 @@ func (l *LexerATNConfig) hash() int {
 }
 
 func (l *LexerATNConfig) equals(other interface{}) bool {
+	return l.gequals(other.(Collectable[ATNConfig]))
+}
+
+func (l *LexerATNConfig) gequals(other Collectable[ATNConfig]) bool {
 	var othert, ok = other.(*LexerATNConfig)
 
 	if l == other {
@@ -287,7 +296,6 @@ func (l *LexerATNConfig) equals(other interface{}) bool {
 	return l.BaseATNConfig.equals(othert.BaseATNConfig)
 }
 
-
 func checkNonGreedyDecision(source *LexerATNConfig, target ATNState) bool {
 	var ds, ok = target.(DecisionState)
 

runtime/Go/antlr/atn_config_set.go

@@ -214,6 +214,33 @@ func (b *BaseATNConfigSet) AddAll(coll []ATNConfig) bool {
 	return false
 }
 
+// Compare is a hack function just to verify that adding DFAstares to the known
+// set works, so long as comparison of ATNConfigSet s works. For that to work, we
+// need to make sure that the set of ATNConfigs in two sets are equivalent. We can't
+// know the order, so we do this inefficient hack. If this proves the point, then
+// we can change the config set to a better structure.
+func (b *BaseATNConfigSet) Compare(bs *BaseATNConfigSet) bool {
+	if len(b.configs) != len(bs.configs) {
+		return false
+	}
+
+	for _, c := range b.configs {
+		found := false
+		for _, c2 := range bs.configs {
+			if c.equals(c2) {
+				found = true
+				break
+			}
+		}
+
+		if !found {
+			return false
+		}
+
+	}
+	return true
+}
+
 func (b *BaseATNConfigSet) Equals(other interface{}) bool {
 	if b == other {
 		return true
@@ -224,12 +251,12 @@ func (b *BaseATNConfigSet) Equals(other interface{}) bool {
 	other2 := other.(*BaseATNConfigSet)
 
 	return b.configs != nil &&
-		// TODO: b.configs.equals(other2.configs) && // TODO: Is b necessary?
 		b.fullCtx == other2.fullCtx &&
 		b.uniqueAlt == other2.uniqueAlt &&
 		b.conflictingAlts == other2.conflictingAlts &&
 		b.hasSemanticContext == other2.hasSemanticContext &&
-		b.dipsIntoOuterContext == other2.dipsIntoOuterContext
+		b.dipsIntoOuterContext == other2.dipsIntoOuterContext &&
+		b.Compare(other2)
 }
 
 func (b *BaseATNConfigSet) hash() int {

runtime/Go/antlr/dfa.go

@@ -4,19 +4,21 @@
 
 package antlr
 
-import (
-	"sort"
-)
-
 type DFA struct {
 	// atnStartState is the ATN state in which this was created
 	atnStartState DecisionState
 
 	decision int
 
 	// states is all the DFA states. Use Map to get the old state back; Set can only
-	// indicate whether it is there.
-	states map[int]*DFAState
+	// indicate whether it is there. Go maps implement key hash collisions and so on and are very
+	// good, but the DFAState is an object and can't be used directly as the key as it can in say JAva
+	// amd C#, whereby if the hashcode is the same for two objects, then equals() is called against them
+	// to see if they really are the same object.
+	//
+	//
+	states    *JStore[*DFAState, *DFAStateComparator[*DFAState]]
+	numstates int
 
 	s0 *DFAState
 
@@ -29,7 +31,7 @@ func NewDFA(atnStartState DecisionState, decision int) *DFA {
 	dfa := &DFA{
 		atnStartState: atnStartState,
 		decision:      decision,
-		states:        make(map[int]*DFAState),
+		states:        NewJStore[*DFAState, *DFAStateComparator[*DFAState]](&DFAStateComparator[*DFAState]{}),
 	}
 	if s, ok := atnStartState.(*StarLoopEntryState); ok && s.precedenceRuleDecision {
 		dfa.precedenceDfa = true
@@ -92,7 +94,8 @@ func (d *DFA) getPrecedenceDfa() bool {
 // true or nil otherwise, and d.precedenceDfa is updated.
 func (d *DFA) setPrecedenceDfa(precedenceDfa bool) {
 	if d.getPrecedenceDfa() != precedenceDfa {
-		d.setStates(make(map[int]*DFAState))
+		d.states = NewJStore[*DFAState, *DFAStateComparator[*DFAState]](&DFAStateComparator[*DFAState]{})
+		d.numstates = 0
 
 		if precedenceDfa {
 			precedenceState := NewDFAState(-1, NewBaseATNConfigSet(false))
@@ -117,38 +120,12 @@ func (d *DFA) setS0(s *DFAState) {
 	d.s0 = s
 }
 
-func (d *DFA) getState(hash int) (*DFAState, bool) {
-	s, ok := d.states[hash]
-	return s, ok
-}
-
-func (d *DFA) setStates(states map[int]*DFAState) {
-	d.states = states
-}
-
-func (d *DFA) setState(hash int, state *DFAState) {
-	d.states[hash] = state
-}
-
-func (d *DFA) numStates() int {
-	return len(d.states)
-}
-
-type dfaStateList []*DFAState
-
-func (d dfaStateList) Len() int           { return len(d) }
-func (d dfaStateList) Less(i, j int) bool { return d[i].stateNumber < d[j].stateNumber }
-func (d dfaStateList) Swap(i, j int)      { d[i], d[j] = d[j], d[i] }
-
 // sortedStates returns the states in d sorted by their state number.
 func (d *DFA) sortedStates() []*DFAState {
-	vs := make([]*DFAState, 0, len(d.states))
-
-	for _, v := range d.states {
-		vs = append(vs, v)
-	}
 
-	sort.Sort(dfaStateList(vs))
+	vs := d.states.SortedSlice(func(i, j *DFAState) bool {
+		return i.stateNumber < j.stateNumber
+	})
 
 	return vs
 }

runtime/Go/antlr/dfa_state.go

@@ -81,6 +81,45 @@ type DFAState struct {
 	predicates []*PredPrediction
 }
 
+type DFAStateComparator[T Collectable[T]] struct {
+}
+
+// NB This is the same as normal DFAState
+func (c *DFAStateComparator[T]) equals(o1, o2 T) bool {
+	return o1.gequals(o2)
+}
+
+// NB This is the same as normal DFAState
+func (c *DFAStateComparator[T]) hash(o T) int {
+	return o.hash()
+}
+
+// equals returns true if this DFA state is equal to another DFA state.
+// Two [DFAState] instances are equal if their ATN configuration sets
+// are the same. This method is used to see if a state already exists.
+//
+// Because the number of alternatives and number of ATN configurations are
+// finite, there is a finite number of DFA states that can be processed.
+// This is necessary to show that the algorithm terminates.
+//
+// Cannot test the DFA state numbers here because in [ParserATNSimulator.addDFAState]
+// we need to know if any other state exists that has this exact set of ATN configurations. The
+// [stateNumber] is irrelevant.
+func (d *DFAState) gequals(o Collectable[*DFAState]) bool {
+	if d == o {
+		return true
+	}
+
+	return d.configs.Equals(o.(*DFAState).configs)
+}
+func (d *DFAState) equals(o interface{}) bool {
+	if d == o {
+		return true
+	}
+
+	return d.configs.Equals(o.(*DFAState).configs)
+}
+
 func NewDFAState(stateNumber int, configs ATNConfigSet) *DFAState {
 	if configs == nil {
 		configs = NewBaseATNConfigSet(false)
@@ -141,15 +180,15 @@ func (d *DFAState) setPrediction(v int) {
 // Cannot test the DFA state numbers here because in
 // ParserATNSimulator.addDFAState we need to know if any other state exists that
 // has d exact set of ATN configurations. The stateNumber is irrelevant.
-func (d *DFAState) equals(other interface{}) bool {
-	if d == other {
-		return true
-	} else if _, ok := other.(*DFAState); !ok {
-		return false
-	}
-
-	return d.configs.Equals(other.(*DFAState).configs)
-}
+// func (d *DFAState) equals(other interface{}) bool {
+//	if d == other {
+//		return true
+//	} else if _, ok := other.(*DFAState); !ok {
+//		return false
+//	}
+//
+//	return d.configs.Equals(other.(*DFAState).configs)
+//}
 
 func (d *DFAState) String() string {
 	var s string
@@ -169,3 +208,12 @@ func (d *DFAState) hash() int {
 	h = murmurUpdate(h, d.configs.hash())
 	return murmurFinish(h, 1)
 }
+
+func (d *DFAState) Equals(o *DFAState) bool {
+
+	if d == o {
+		return true
+	}
+
+	return d.configs.Equals(o.configs)
+}

runtime/Go/antlr/go.mod

@@ -1,3 +1,3 @@
 module github.com/antlr/antlr4/runtime/Go/antlr
 
-go 1.16
+go 1.18