chore(gnovm): use blank identifier constants (gnolang#2158)

Replaces "_" with blank identifier constants.

gnovm/pkg/gnolang/helpers.go

@@ -91,7 +91,7 @@ func Flds(args ...interface{}) FieldTypeExprs {
 
 func Recv(n, t interface{}) FieldTypeExpr {
 	if n == "" {
-		n = "_"
+		n = blankIdentifier
 	}
 	return FieldTypeExpr{
 		Name: N(n),

gnovm/pkg/gnolang/machine.go

@@ -315,7 +315,7 @@ func checkDuplicates(fset *FileSet) bool {
 				name = d.Name
 			case *ValueDecl:
 				for _, nx := range d.NameExprs {
-					if nx.Name == "_" {
+					if nx.Name == blankIdentifier {
 						continue
 					}
 					if _, ok := defined[nx.Name]; ok {
@@ -327,7 +327,7 @@ func checkDuplicates(fset *FileSet) bool {
 			default:
 				continue
 			}
-			if name == "_" {
+			if name == blankIdentifier {
 				continue
 			}
 			if _, ok := defined[name]; ok {

gnovm/pkg/gnolang/nodes.go

@@ -1014,7 +1014,7 @@ type ValueDecl struct {
 func (x *ValueDecl) GetDeclNames() []Name {
 	ns := make([]Name, 0, len(x.NameExprs))
 	for _, nx := range x.NameExprs {
-		if nx.Name == "_" {
+		if nx.Name == blankIdentifier {
 			// ignore
 		} else {
 			ns = append(ns, nx.Name)
@@ -1031,7 +1031,7 @@ type TypeDecl struct {
 }
 
 func (x *TypeDecl) GetDeclNames() []Name {
-	if x.NameExpr.Name == "_" {
+	if x.NameExpr.Name == blankIdentifier {
 		return nil // ignore
 	} else {
 		return []Name{x.NameExpr.Name}
@@ -1588,8 +1588,8 @@ func (sb *StaticBlock) GetParentNode(store Store) BlockNode {
 // Implements BlockNode.
 // As a side effect, notes externally defined names.
 func (sb *StaticBlock) GetPathForName(store Store, n Name) ValuePath {
-	if n == "_" {
-		return NewValuePathBlock(0, 0, "_")
+	if n == blankIdentifier {
+		return NewValuePathBlock(0, 0, blankIdentifier)
 	}
 	// Check local.
 	gen := 1
@@ -1780,7 +1780,7 @@ func (sb *StaticBlock) Define2(isConst bool, n Name, st Type, tv TypedValue) {
 	if tv.T == nil && tv.V != nil {
 		panic("StaticBlock.Define2() requires .T if .V is set")
 	}
-	if n == "_" {
+	if n == blankIdentifier {
 		return // ignore
 	}
 	idx, exists := sb.GetLocalIndex(n)

gnovm/pkg/gnolang/op_eval.go

@@ -47,7 +47,7 @@ func (m *Machine) doOpEval() {
 		m.PopExpr()
 		switch x.Kind {
 		case INT:
-			x.Value = strings.ReplaceAll(x.Value, "_", "")
+			x.Value = strings.ReplaceAll(x.Value, blankIdentifier, "")
 			// temporary optimization
 			bi := big.NewInt(0)
 			// TODO optimize.
@@ -84,7 +84,7 @@ func (m *Machine) doOpEval() {
 				V: BigintValue{V: bi},
 			})
 		case FLOAT:
-			x.Value = strings.ReplaceAll(x.Value, "_", "")
+			x.Value = strings.ReplaceAll(x.Value, blankIdentifier, "")
 
 			if reFloat.MatchString(x.Value) {
 				value := x.Value

gnovm/pkg/gnolang/preprocess.go

@@ -9,7 +9,9 @@ import (
 	"github.com/gnolang/gno/tm2/pkg/errors"
 )
 
-const blankIdentifer string = "_"
+const (
+	blankIdentifier = "_"
+)
 
 // In the case of a *FileSet, some declaration steps have to happen
 // in a restricted parallel way across all the files.
@@ -191,7 +193,7 @@ func Preprocess(store Store, ctx BlockNode, n Node) Node {
 					var defined bool
 					for _, lx := range n.Lhs {
 						ln := lx.(*NameExpr).Name
-						if ln == "_" {
+						if ln == blankIdentifier {
 							// ignore.
 						} else {
 							_, ok := last.GetLocalIndex(ln)
@@ -235,7 +237,7 @@ func Preprocess(store Store, ctx BlockNode, n Node) Node {
 			case *FuncTypeExpr:
 				for i := range n.Params {
 					p := &n.Params[i]
-					if p.Name == "" || p.Name == "_" {
+					if p.Name == "" || p.Name == blankIdentifier {
 						// create a hidden var with leading dot.
 						// NOTE: document somewhere.
 						pn := fmt.Sprintf(".arg_%d", i)
@@ -244,7 +246,7 @@ func Preprocess(store Store, ctx BlockNode, n Node) Node {
 				}
 				for i := range n.Results {
 					r := &n.Results[i]
-					if r.Name == "_" {
+					if r.Name == blankIdentifier {
 						// create a hidden var with leading dot.
 						// NOTE: document somewhere.
 						rn := fmt.Sprintf(".res_%d", i)
@@ -683,8 +685,8 @@ func Preprocess(store Store, ctx BlockNode, n Node) Node {
 				}
 				// specific and general cases
 				switch n.Name {
-				case "_":
-					n.Path = NewValuePathBlock(0, 0, "_")
+				case blankIdentifier:
+					n.Path = NewValuePathBlock(0, 0, blankIdentifier)
 					return n, TRANS_CONTINUE
 				case "iota":
 					pd := lastDecl(ns)
@@ -1246,7 +1248,7 @@ func Preprocess(store Store, ctx BlockNode, n Node) Node {
 				}
 
 				// Type assertions on the blank identifier are illegal.
-				if nx, ok := n.X.(*NameExpr); ok && string(nx.Name) == blankIdentifer {
+				if nx, ok := n.X.(*NameExpr); ok && string(nx.Name) == blankIdentifier {
 					panic("cannot use _ as value or type")
 				}
 
@@ -1929,8 +1931,8 @@ func Preprocess(store Store, ctx BlockNode, n Node) Node {
 					pn := fn.GetParentNode(nil).(*PackageNode)
 					for i := 0; i < numNames; i++ {
 						nx := &n.NameExprs[i]
-						if nx.Name == "_" {
-							nx.Path = NewValuePathBlock(0, 0, "_")
+						if nx.Name == blankIdentifier {
+							nx.Path = NewValuePathBlock(0, 0, blankIdentifier)
 						} else {
 							pn.Define2(n.Const, nx.Name, sts[i], tvs[i])
 							nx.Path = last.GetPathForName(nil, nx.Name)
@@ -1939,8 +1941,8 @@ func Preprocess(store Store, ctx BlockNode, n Node) Node {
 				} else {
 					for i := 0; i < numNames; i++ {
 						nx := &n.NameExprs[i]
-						if nx.Name == "_" {
-							nx.Path = NewValuePathBlock(0, 0, "_")
+						if nx.Name == blankIdentifier {
+							nx.Path = NewValuePathBlock(0, 0, blankIdentifier)
 						} else {
 							last.Define2(n.Const, nx.Name, sts[i], tvs[i])
 							nx.Path = last.GetPathForName(nil, nx.Name)
@@ -3054,7 +3056,7 @@ func predefineNow2(store Store, last BlockNode, d Decl, m map[Name]struct{}) (De
 		// NOTE: unlike the *ValueDecl case, this case doesn't
 		// preprocess d itself (only d.Type).
 		if cd.IsMethod {
-			if cd.Recv.Name == "" || cd.Recv.Name == "_" {
+			if cd.Recv.Name == "" || cd.Recv.Name == blankIdentifier {
 				// create a hidden var with leading dot.
 				// NOTE: document somewhere.
 				cd.Recv.Name = ".recv"
@@ -3173,7 +3175,7 @@ func tryPredefine(store Store, last BlockNode, d Decl) (un Name) {
 		}
 		if d.Name == "" { // use default
 			d.Name = pv.PkgName
-		} else if d.Name == "_" { // no definition
+		} else if d.Name == blankIdentifier { // no definition
 			return
 		} else if d.Name == "." { // dot import
 			panic("dot imports not allowed in Gno")
@@ -3200,8 +3202,8 @@ func tryPredefine(store Store, last BlockNode, d Decl) (un Name) {
 		}
 		for i := 0; i < len(d.NameExprs); i++ {
 			nx := &d.NameExprs[i]
-			if nx.Name == "_" {
-				nx.Path.Name = "_"
+			if nx.Name == blankIdentifier {
+				nx.Path.Name = blankIdentifier
 			} else {
 				last2 := skipFile(last)
 				last2.Predefine(d.Const, nx.Name)
@@ -3381,7 +3383,7 @@ func constUntypedBigint(source Expr, i64 int64) *ConstExpr {
 }
 
 func fillNameExprPath(last BlockNode, nx *NameExpr, isDefineLHS bool) {
-	if nx.Name == "_" {
+	if nx.Name == blankIdentifier {
 		// Blank name has no path; caller error.
 		panic("should not happen")
 	}

gnovm/pkg/gnolang/values.go

@@ -2344,7 +2344,7 @@ func (b *Block) GetPointerToInt(store Store, index int) PointerValue {
 func (b *Block) GetPointerTo(store Store, path ValuePath) PointerValue {
 	if path.IsBlockBlankPath() {
 		if debug {
-			if path.Name != "_" {
+			if path.Name != blankIdentifier {
 				panic(fmt.Sprintf(
 					"zero value path is reserved for \"_\", but got %s",
 					path.Name))