Merge pull request #629 from nspcc-dev/feature/panic

compiler: support panic builtin

pkg/compiler/analysis.go

@@ -16,6 +16,7 @@ var (
 		"SHA1", "Hash256", "Hash160",
 		"VerifySignature", "AppCall",
 		"FromAddress", "Equals",
+		"panic",
 	}
 )
 
@@ -69,6 +70,12 @@ func isIdentBool(ident *ast.Ident) bool {
 	return ident.Name == "true" || ident.Name == "false"
 }
 
+// isExprNil looks if the given expression is a `nil`.
+func isExprNil(e ast.Expr) bool {
+	v, ok := e.(*ast.Ident)
+	return ok && v.Name == "nil"
+}
+
 // makeBoolFromIdent creates a bool type from an *ast.Ident.
 func makeBoolFromIdent(ident *ast.Ident, tinfo *types.Info) (types.TypeAndValue, error) {
 	var b bool
@@ -180,16 +187,6 @@ func isBuiltin(expr ast.Expr) bool {
 	return false
 }
 
-func isAppCall(expr ast.Expr) bool {
-	t, ok := expr.(*ast.SelectorExpr)
-	return ok && t.Sel.Name == "AppCall"
-}
-
-func isFromAddress(expr ast.Expr) bool {
-	t, ok := expr.(*ast.SelectorExpr)
-	return ok && t.Sel.Name == "FromAddress"
-}
-
 func isByteArray(lit *ast.CompositeLit, tInfo *types.Info) bool {
 	if len(lit.Elts) == 0 {
 		return false

pkg/compiler/codegen.go

@@ -523,17 +523,7 @@ func (c *codegen) Visit(node ast.Node) ast.Visitor {
 			return nil
 		}
 
-		args := n.Args
+		args := transformArgs(n.Fun, n.Args)
-		isAppCall := isAppCall(n.Fun)
-		isFromAddress := isFromAddress(n.Fun)
-		// There are 2 special cases:
-		// 1. When using APPCALL, script hash is a part of the instruction so
-		//    script hash should be emitted after APPCALL.
-		// 2. With FromAddress, parameter conversion is happening at compile-time
-		//    so there is no need to push parameters on stack and perform an actual call
-		if isAppCall || isFromAddress {
-			args = n.Args[1:]
-		}
 
 		// Handle the arguments
 		for _, arg := range args {
@@ -560,16 +550,6 @@ func (c *codegen) Visit(node ast.Node) ast.Visitor {
 			// Use the ident to check, builtins are not in func scopes.
 			// We can be sure builtins are of type *ast.Ident.
 			c.convertBuiltin(n)
-
-			if isAppCall {
-				buf := c.getByteArray(n.Args[0])
-				if len(buf) != 20 {
-					c.prog.Err = errors.New("invalid script hash")
-					return nil
-				}
-
-				c.prog.WriteBytes(buf)
-			}
 		case isSyscall(f):
 			c.convertSyscall(f.selector.Name, f.name)
 		default:
@@ -764,12 +744,22 @@ func (c *codegen) convertBuiltin(expr *ast.CallExpr) {
 		if isByteArrayType(typ) {
 			emitOpcode(c.prog.BinWriter, opcode.CAT)
 		} else {
+			emitOpcode(c.prog.BinWriter, opcode.OVER)
 			emitOpcode(c.prog.BinWriter, opcode.SWAP)
-			emitOpcode(c.prog.BinWriter, opcode.DUP)
-			emitOpcode(c.prog.BinWriter, opcode.PUSH2)
-			emitOpcode(c.prog.BinWriter, opcode.XSWAP)
 			emitOpcode(c.prog.BinWriter, opcode.APPEND)
 		}
+	case "panic":
+		arg := expr.Args[0]
+		if isExprNil(arg) {
+			emitOpcode(c.prog.BinWriter, opcode.DROP)
+			emitOpcode(c.prog.BinWriter, opcode.THROW)
+		} else if isStringType(c.typeInfo.Types[arg].Type) {
+			ast.Walk(c, arg)
+			emitSyscall(c.prog.BinWriter, "Neo.Runtime.Log")
+			emitOpcode(c.prog.BinWriter, opcode.THROW)
+		} else {
+			c.prog.Err = errors.New("panic should have string or nil argument")
+		}
 	case "SHA256":
 		emitOpcode(c.prog.BinWriter, opcode.SHA256)
 	case "SHA1":
@@ -782,6 +772,12 @@ func (c *codegen) convertBuiltin(expr *ast.CallExpr) {
 		emitOpcode(c.prog.BinWriter, opcode.VERIFY)
 	case "AppCall":
 		emitOpcode(c.prog.BinWriter, opcode.APPCALL)
+		buf := c.getByteArray(expr.Args[0])
+		if len(buf) != 20 {
+			c.prog.Err = errors.New("invalid script hash")
+		}
+
+		c.prog.WriteBytes(buf)
 	case "Equals":
 		emitOpcode(c.prog.BinWriter, opcode.EQUAL)
 	case "FromAddress":
@@ -800,6 +796,30 @@ func (c *codegen) convertBuiltin(expr *ast.CallExpr) {
 	}
 }
 
+// transformArgs returns a list of function arguments
+// which should be put on stack.
+// There are special cases for builtins:
+// 1. When using AppCall, script hash is a part of the instruction so
+//    it should be emitted after APPCALL.
+// 2. With FromAddress, parameter conversion is happening at compile-time
+//    so there is no need to push parameters on stack and perform an actual call
+// 3. With panic, generated code depends on if argument was nil or a string so
+//    it should be handled accordingly.
+func transformArgs(fun ast.Expr, args []ast.Expr) []ast.Expr {
+	switch f := fun.(type) {
+	case *ast.SelectorExpr:
+		if f.Sel.Name == "AppCall" || f.Sel.Name == "FromAddress" {
+			return args[1:]
+		}
+	case *ast.Ident:
+		if f.Name == "panic" {
+			return args[1:]
+		}
+	}
+
+	return args
+}
+
 func (c *codegen) convertByteArray(lit *ast.CompositeLit) {
 	buf := make([]byte, len(lit.Elts))
 	for i := 0; i < len(lit.Elts); i++ {

pkg/compiler/panic_test.go

@@ -0,0 +1,71 @@
+package compiler_test
+
+import (
+	"fmt"
+	"math/big"
+	"testing"
+
+	"github.com/CityOfZion/neo-go/pkg/vm"
+	"github.com/stretchr/testify/require"
+)
+
+func TestPanic(t *testing.T) {
+	t.Run("no panic", func(t *testing.T) {
+		src := getPanicSource(false, `"execution fault"`)
+		eval(t, src, big.NewInt(7))
+	})
+
+	t.Run("panic with message", func(t *testing.T) {
+		var logs []string
+		src := getPanicSource(true, `"execution fault"`)
+		v := vmAndCompile(t, src)
+		v.RegisterInteropGetter(logGetter(&logs))
+
+		require.Error(t, v.Run())
+		require.True(t, v.HasFailed())
+		require.Equal(t, 1, len(logs))
+		require.Equal(t, "execution fault", logs[0])
+	})
+
+	t.Run("panic with nil", func(t *testing.T) {
+		var logs []string
+		src := getPanicSource(true, `nil`)
+		v := vmAndCompile(t, src)
+		v.RegisterInteropGetter(logGetter(&logs))
+
+		require.Error(t, v.Run())
+		require.True(t, v.HasFailed())
+		require.Equal(t, 0, len(logs))
+	})
+}
+
+func getPanicSource(need bool, message string) string {
+	return fmt.Sprintf(`
+	package main
+	func Main() int {
+		needPanic := %#v
+		if needPanic {
+			panic(%s)
+			return 5
+		}
+		return 7
+	}
+	`, need, message)
+}
+
+func logGetter(logs *[]string) vm.InteropGetterFunc {
+	logID := vm.InteropNameToID([]byte("Neo.Runtime.Log"))
+	return func(id uint32) *vm.InteropFuncPrice {
+		if id != logID {
+			return nil
+		}
+
+		return &vm.InteropFuncPrice{
+			Func: func(v *vm.VM) error {
+				msg := string(v.Estack().Pop().Bytes())
+				*logs = append(*logs, msg)
+				return nil
+			},
+		}
+	}
+}