fix: labels error handling

gnovm/pkg/gnolang/gno_test.go

@@ -17,6 +17,92 @@ import (
 	"github.com/jaekwon/testify/require"
 )
 
+func TestRunInvalidLabels(t *testing.T) {
+	tests := []struct {
+		code   string
+		output string
+	}{
+		{
+			code: `
+		package test
+		func main(){}
+		func invalidLabel() {
+			FirstLoop:
+				for i := 0; i < 10; i++ {
+				}
+				for i := 0; i < 10; i++ {
+					break FirstLoop
+				}
+		}
+`,
+			output: `cannot find branch label "FirstLoop"`,
+		},
+		{
+			code: `
+		package test
+		func main(){}
+
+		func undefinedLabel() {
+			for i := 0; i < 10; i++ {
+				break UndefinedLabel
+			}
+		}
+`,
+			output: `label UndefinedLabel undefined`,
+		},
+		{
+			code: `
+		package test
+		func main(){}
+
+		func labelOutsideScope() {
+			for i := 0; i < 10; i++ {
+				continue FirstLoop
+			}
+			FirstLoop:
+			for i := 0; i < 10; i++ {
+			}
+		}
+`,
+			output: `cannot find branch label "FirstLoop"`,
+		},
+		{
+			code: `
+		package test
+		func main(){}
+
+		func invalidLabelStatement() {
+			if true {
+				break InvalidLabel
+			}
+		}
+`,
+			output: `label InvalidLabel undefined`,
+		},
+	}
+
+	for n, s := range tests {
+		n := n
+		t.Run(fmt.Sprintf("%v\n", n), func(t *testing.T) {
+			defer func() {
+				if r := recover(); r != nil {
+					es := fmt.Sprintf("%v\n", r)
+					if !strings.Contains(es, s.output) {
+						t.Fatalf("invalid label test: `%v` missing expected error: %+v got: %v\n", n, s.output, es)
+					}
+				} else {
+					t.Fatalf("invalid label test: `%v` should have failed but didn't\n", n)
+				}
+			}()
+
+			m := NewMachine("test", nil)
+			nn := MustParseFile("main.go", s.code)
+			m.RunFiles(nn)
+			m.RunMain()
+		})
+	}
+}
+
 func TestBuiltinIdentifiersShadowing(t *testing.T) {
 	t.Parallel()
 	tests := map[string]string{}

gnovm/pkg/gnolang/preprocess.go

@@ -1659,7 +1659,14 @@ func Preprocess(store Store, ctx BlockNode, n Node) Node {
 			case *BranchStmt:
 				switch n.Op {
 				case BREAK:
+					if !isSwitchLabel(ns, n.Label) {
+						findBranchLabel(last, n.Label)
+					}
 				case CONTINUE:
+					if isSwitchLabel(ns, n.Label) {
+						panic(fmt.Sprintf("invalid continue label %q\n", n.Label))
+					}
+					findBranchLabel(last, n.Label)
 				case GOTO:
 					_, depth, index := findGotoLabel(last, n.Label)
 					n.Depth = depth
@@ -1977,6 +1984,23 @@ func Preprocess(store Store, ctx BlockNode, n Node) Node {
 	return nn
 }
 
+func isSwitchLabel(ns []Node, label Name) bool {
+	for {
+		swch := lastSwitch(ns)
+		if swch == nil {
+			break
+		}
+
+		if swch.GetLabel() == label && label != "" {
+			return true
+		}
+
+		ns = ns[:len(ns)-1]
+	}
+
+	return false
+}
+
 func pushInitBlock(bn BlockNode, last *BlockNode, stack *[]BlockNode) {
 	if !bn.IsInitialized() {
 		bn.InitStaticBlock(bn, *last)
@@ -2245,6 +2269,46 @@ func funcOf(last BlockNode) (BlockNode, *FuncTypeExpr) {
 	}
 }
 
+func findBranchLabel(last BlockNode, label Name) (
+	bn BlockNode, depth uint8, bodyIdx int,
+) {
+	for {
+		switch cbn := last.(type) {
+		case *BlockStmt, *ForStmt, *IfCaseStmt, *RangeStmt, *SelectCaseStmt, *SwitchClauseStmt, *SwitchStmt:
+			lbl := cbn.GetLabel()
+			if label == lbl {
+				bn = cbn
+				return
+			}
+			last = cbn.GetParentNode(nil)
+			depth += 1
+		case *IfStmt:
+			// These are faux blocks -- shouldn't happen.
+			panic("unexpected faux blocknode")
+		case *FileNode:
+			panic("unexpected file blocknode")
+		case *PackageNode:
+			panic("unexpected package blocknode")
+		case *FuncLitExpr:
+			body := cbn.GetBody()
+			_, bodyIdx = body.GetLabeledStmt(label)
+			if bodyIdx != -1 {
+				bn = cbn
+				return
+			}
+			panic(fmt.Sprintf(
+				"cannot find branch label %q",
+				label))
+		case *FuncDecl:
+			panic(fmt.Sprintf(
+				"cannot find branch label %q",
+				label))
+		default:
+			panic("unexpected block node")
+		}
+	}
+}
+
 func findGotoLabel(last BlockNode, label Name) (
 	bn BlockNode, depth uint8, bodyIdx int,
 ) {