fix: PCount, Break/RECOVER, SET INDEX TO — 3 Harbour compat fixes

Release-blocking compatibility issues discovered during the 258-test
pre-release validation suite (100 syntax + 44 RDD + 114 RTL).

1. PCount() always returned 0 in PRG code

   Root cause: ParamCount() returned t.pendingParams, which is
   overwritten by every nested Function() call. By the time the
   PCount() RTL's Frame() executes, pendingParams is already 0.

   Fix: Frame() now stores pendingParams in frame.paramCount.
   PCount() RTL uses CallerParamCount() which reads callSP-2
   (the PRG caller's frame), while RTL functions still use
   ParamCount() (reads pendingParams before their own Frame).

   Verified: PCount(1,2,3)=3, PCount(1)=1, PCount()=0

2. Break("string") panicked instead of being caught by RECOVER USING

   Root cause: Generated SEQUENCE code only caught *HbError panics.
   Break() panics with BreakValue (a different type), which fell
   through to EndProc's "runtime error" message and re-panic.

   Fix (two parts):
   a) gengo emitBeginSequence: recover closure now catches any
      panic (interface{}), then dispatches via type switch:
      - *HbError → extract .Error() string
      - hasValue interface (BreakValue) → extract .GetValue()
      - other → static "error" string
   b) hbrtl/error.go: BreakValue gets GetValue() method for
      duck-type detection without import cycles
   c) hbrt/thread.go EndProc: BreakValue type name check added
      so it re-panics silently (no stderr noise)

3. SET INDEX TO a, b, c only opened the last file

   Root cause: Parser's parseSet() called parseExpr() once for
   INDEX setting, stopping at the first comma. Remaining file
   names were consumed by the "eat rest of line" loop.

   Fix: Parser now collects comma-separated identifiers into a
   single string literal "a,b,c". gengo splits on comma and
   calls OrderListAdd() for each file.

   Verified: SET INDEX TO si_name, si_city → OrdCount=2

All tests pass:
  go test ./...          14 packages OK
  FiveSql2               43/43  100%
  compat_harbour         51/51
  Syntax test           100/100
  RDD test               44/44
  RTL test              114/114
  Windows cross-compile  OK
  Linux cross-compile    OK

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

compiler/gengo/gengo.go

@@ -655,12 +655,20 @@ func (g *Generator) emitStmt(stmt ast.Stmt, locals localMap) {
 				g.writeln("if idx, ok := area.(hbrdd.Indexer); ok {")
 				g.indent++
 				if fileStr != "" {
-					// Strip surrounding quotes from string literals
+					// SET INDEX TO a, b, c — split comma-separated file names
+					// and call OrderListAdd for each. Harbour loads all NTX
+					// files into the active index list.
 					clean := fileStr
 					if len(clean) >= 2 && clean[0] == '"' && clean[len(clean)-1] == '"' {
 						clean = clean[1 : len(clean)-1]
 					}
-					g.writeln(fmt.Sprintf(`idx.OrderListAdd(%q)`, clean))
+					parts := strings.Split(clean, ",")
+					for _, p := range parts {
+						p = strings.TrimSpace(p)
+						if p != "" {
+							g.writeln(fmt.Sprintf(`idx.OrderListAdd(%q)`, p))
+						}
+					}
 				} else {
 					g.emitExpr(s.Expr)
 					g.writeln(`idx.OrderListAdd(t.Pop2().AsString())`)
@@ -1329,19 +1337,18 @@ func (g *Generator) emitSwitch(s *ast.SwitchStmt, locals localMap) {
 
 func (g *Generator) emitBeginSequence(s *ast.SeqStmt, locals localMap) {
 	// BEGIN SEQUENCE → Go's panic/recover.
-	// Use a _seqBreak flag to signal Break() was called.
+	// Catches both *HbError (runtime errors) and BreakValue (Break() calls).
-	// Break() panics with *HbError, caught by our recover.
+	// BreakValue is defined in hbrtl, but we detect it via duck typing
+	// to avoid import cycles.
 	g.writeln("{ // BEGIN SEQUENCE")
 	g.indent++
-	g.writeln("_seqErr := func() (_recoverErr *hbrt.HbError) {")
+	g.writeln("_seqErr := func() (_recoverVal interface{}) {")
 	g.indent++
 	g.writeln("defer func() {")
 	g.indent++
 	g.writeln("if r := recover(); r != nil {")
 	g.indent++
-	g.writeln("if hbErr, ok := r.(*hbrt.HbError); ok {")
+	g.writeln("_recoverVal = r")
-	g.writeln("  _recoverErr = hbErr")
-	g.writeln("} else { panic(r) }")
 	g.indent--
 	g.writeln("}")
 	g.indent--
@@ -1362,7 +1369,27 @@ func (g *Generator) emitBeginSequence(s *ast.SeqStmt, locals localMap) {
 		g.indent++
 		if s.RecoverVar != "" {
 			if idx, found := locals[strings.ToUpper(s.RecoverVar)]; found {
-				g.writeln(fmt.Sprintf("t.SetLocalFast(%d, hbrt.MakeString(_seqErr.Error()))", idx))
+				// Extract the value from the recovered panic:
+				//   *HbError → error description string
+				//   BreakValue (has .Value field) → the Break() argument
+				//   other → string representation
+				g.writeln(fmt.Sprintf(`{ // RECOVER USING %s`, s.RecoverVar))
+				g.indent++
+				g.writeln(`switch _sv := _seqErr.(type) {`)
+				g.writeln(`case *hbrt.HbError:`)
+				g.writeln(fmt.Sprintf(`  t.SetLocalFast(%d, hbrt.MakeString(_sv.Error()))`, idx))
+				g.writeln(`default:`)
+				// For BreakValue, use reflection-free approach: check if
+				// the type has a Value field via a local interface.
+				g.writeln(`  type hasValue interface{ GetValue() hbrt.Value }`)
+				g.writeln(`  if bv, ok := _sv.(hasValue); ok {`)
+				g.writeln(fmt.Sprintf(`    t.SetLocalFast(%d, bv.GetValue())`, idx))
+				g.writeln(`  } else {`)
+				g.writeln(fmt.Sprintf(`    t.SetLocalFast(%d, hbrt.MakeString("error"))`, idx))
+				g.writeln(`  }`)
+				g.writeln(`}`)
+				g.indent--
+				g.writeln(`}`)
 			}
 		}
 		for _, stmt := range s.RecoverBody {

compiler/parser/parser.go

@@ -1781,6 +1781,35 @@ func (p *Parser) parseSet() *ast.SetCmd {
 		if upperSetting == "FILTER" || upperSetting == "RELATION" || upperSetting == "ORDER" || upperSetting == "INDEX" {
 			if p.current.Kind != token.NEWLINE && p.current.Kind != token.EOF {
 				expr = p.parseExpr()
+				// SET INDEX TO a, b, c — collect comma-separated file names
+				// into a single string literal "a,b,c" for gengo to split.
+				if upperSetting == "INDEX" {
+					getName := func(e ast.Expr) string {
+						switch v := e.(type) {
+						case *ast.IdentExpr:
+							return v.Name
+						case *ast.LiteralExpr:
+							return v.Value
+						default:
+							return ""
+						}
+					}
+					combined := getName(expr)
+					for p.current.Kind == token.COMMA {
+						p.advance()
+						if p.current.Kind != token.NEWLINE && p.current.Kind != token.EOF {
+							next := p.parseExpr()
+							combined += "," + getName(next)
+						}
+					}
+					if strings.Contains(combined, ",") {
+						expr = &ast.LiteralExpr{
+							Value:    combined,
+							Kind:     token.STRING,
+							ValuePos: expr.Pos(),
+						}
+					}
+				}
 			}
 			if p.current.Kind == token.INTO {
 				p.advance()

hbrt/thread.go

@@ -225,7 +225,7 @@ func (t *Thread) Frame(params, locals int) {
 	frame.base = t.sp - actual // only actual args on stack
 	frame.localBase = localBase
 	frame.localCount = params + locals
-	frame.paramCount = params
+	frame.paramCount = t.pendingParams // actual args passed by caller (not declared count)
 	frame.retVal = MakeNil()
 	frame.symbol = t.pendingCallSym
 	t.pendingCallSym = nil
@@ -249,14 +249,23 @@ func (t *Thread) Frame(params, locals int) {
 
 // EndProc is called via defer at the end of every function.
 // Handles recover for BEGIN SEQUENCE and restores frame.
-// HbError panics are re-panicked so the generated SEQUENCE handler can catch them.
+// All panics are re-panicked so the generated SEQUENCE/RECOVER handler
+// can catch them. HbError + BreakValue (from Break() in hbrtl) are
+// re-panicked silently; unknown panics also re-panic but with a
+// diagnostic message on stderr.
 func (t *Thread) EndProc() {
 	if r := recover(); r != nil {
 		t.endFrame()
 		if _, ok := r.(*HbError); ok {
-			panic(r) // re-panic: let BEGIN SEQUENCE's generated recover catch it
+			panic(r) // HbError — re-panic silently
 		}
-		fmt.Fprintf(os.Stderr, "Five runtime error: %v\n", r)
+		// Check for BreakValue from hbrtl.Break() via duck typing.
+		// We can't import hbrtl (cycle), so we check the type name.
+		rType := fmt.Sprintf("%T", r)
+		if rType == "hbrtl.BreakValue" {
+			panic(r) // BreakValue — re-panic silently for RECOVER USING
+		}
+		fmt.Fprintf(os.Stderr, "Five runtime error: %v [recovered, repanicked]\n", r)
 		panic(r)
 	}
 	t.endFrame()
@@ -559,11 +568,25 @@ func (t *Thread) VM() *VM {
 }
 
 // ParamCount returns the number of parameters passed to the current call.
-// Used by variadic RTL functions (QOut, etc.).
+// Used by RTL functions that call ParamCount() BEFORE Frame() — returns
+// pendingParams set by Function(nArgs). This is the original behavior
+// that all existing RTL functions depend on.
+//
+// For PRG-level PCount(), use CallerParamCount() instead (via PCount RTL).
 func (t *Thread) ParamCount() int {
 	return t.pendingParams
 }
 
+// CallerParamCount returns the param count of the calling PRG function
+// (one frame below the current). Used by PCount() RTL which needs the
+// caller's count, not its own.
+func (t *Thread) CallerParamCount() int {
+	if t.callSP >= 2 {
+		return t.calls[t.callSP-2].paramCount
+	}
+	return 0
+}
+
 // PendingParams2 sets pending param count for direct block calls (AEval, ASort etc.)
 func (t *Thread) PendingParams2(n int) {
 	t.pendingParams = n

hbrtl/error.go

@@ -103,6 +103,12 @@ type BreakValue struct {
 	Value hbrt.Value
 }
 
+// GetValue returns the Break() argument. Used by RECOVER USING via duck typing
+// (the generated code checks for a `hasValue` interface to avoid import cycles).
+func (bv BreakValue) GetValue() hbrt.Value {
+	return bv.Value
+}
+
 // Break(xValue) → panics with BreakValue, caught by BEGIN SEQUENCE/RECOVER.
 func Break(t *hbrt.Thread) {
 	nParams := t.ParamCount()

hbrtl/missing.go

@@ -269,11 +269,12 @@ func TypeFunc(t *hbrt.Thread) {
 	t.RetValue()
 }
 
-// PCount returns number of parameters passed.
+// PCount returns number of parameters passed to the calling PRG function.
+// Harbour: hb_pcount() — returns the CALLER's param count, not PCount's own.
 func PCount(t *hbrt.Thread) {
 	t.Frame(0, 0)
 	defer t.EndProcFast()
-	t.RetInt(int64(t.ParamCount()))
+	t.RetInt(int64(t.CallerParamCount()))
 }
 
 // Break moved to error.go — full implementation with BreakValue type.