compiler: set default values for complex struct fields

Set default value also for complex (struct, map) types.
Note: because VM does not distinguish empty array and nil array,
comparison 'a == nil' can't be handled properly without substantial
effort. This will be fixed in NEO3.

pkg/compiler/analysis.go

@@ -44,8 +44,9 @@ func typeAndValueForField(fld *types.Var) (types.TypeAndValue, error) {
 		default:
 			return types.TypeAndValue{}, fmt.Errorf("could not initialize struct field %s to zero, type: %s", fld.Name(), t)
 		}
+	default:
+		return types.TypeAndValue{Type: t}, nil
 	}
-	return types.TypeAndValue{}, nil
 }
 
 // countGlobals counts the global variables in the program to add

pkg/compiler/codegen.go

@@ -533,6 +533,8 @@ func (c *codegen) Visit(node ast.Node) ast.Visitor {
 			c.emitLoadConst(value)
 		} else if tv := c.typeInfo.Types[n]; tv.Value != nil {
 			c.emitLoadConst(tv)
+		} else if n.Name == "nil" {
+			c.emitDefault(new(types.Slice))
 		} else {
 			c.emitLoadLocal(n.Name)
 		}
@@ -1230,11 +1232,32 @@ func (c *codegen) convertStruct(lit *ast.CompositeLit) {
 
 		emit.Opcode(c.prog.BinWriter, opcode.DUP)
 		emit.Int(c.prog.BinWriter, int64(i))
-		c.emitLoadConst(typeAndVal)
+		c.emitDefault(typeAndVal.Type)
 		emit.Opcode(c.prog.BinWriter, opcode.SETITEM)
 	}
 }
 
+func (c *codegen) emitDefault(typ types.Type) {
+	switch t := c.scTypeFromGo(typ); t {
+	case "Integer":
+		emit.Int(c.prog.BinWriter, 0)
+	case "Boolean":
+		emit.Bool(c.prog.BinWriter, false)
+	case "String":
+		emit.String(c.prog.BinWriter, "")
+	case "Map":
+		emit.Opcode(c.prog.BinWriter, opcode.NEWMAP)
+	case "Struct":
+		emit.Int(c.prog.BinWriter, int64(typ.(*types.Struct).NumFields()))
+		emit.Opcode(c.prog.BinWriter, opcode.NEWSTRUCT)
+	case "Array":
+		emit.Int(c.prog.BinWriter, 0)
+		emit.Opcode(c.prog.BinWriter, opcode.NEWARRAY)
+	case "ByteArray":
+		emit.Bytes(c.prog.BinWriter, []byte{})
+	}
+}
+
 func (c *codegen) convertToken(tok token.Token) {
 	switch tok {
 	case token.ADD_ASSIGN:

pkg/compiler/debug.go

@@ -183,7 +183,11 @@ func (c *codegen) scReturnTypeFromScope(scope *funcScope) string {
 }
 
 func (c *codegen) scTypeFromExpr(typ ast.Expr) string {
-	switch t := c.typeInfo.Types[typ].Type.(type) {
+	return c.scTypeFromGo(c.typeInfo.Types[typ].Type)
+}
+
+func (c *codegen) scTypeFromGo(typ types.Type) string {
+	switch t := typ.(type) {
 	case *types.Basic:
 		info := t.Info()
 		switch {

pkg/compiler/struct_test.go

@@ -338,6 +338,29 @@ var structTestCases = []testCase{
 		}`,
 		big.NewInt(2),
 	},
+	{
+		"uninitialized struct fields",
+		`package foo
+		type Foo struct {
+			i int
+			m map[string]int
+			b []byte
+			a []int
+			s struct { ii int }
+		}
+		func NewFoo() Foo { return Foo{} }
+		func Main() int {
+			foo := NewFoo()
+			if foo.i != 0 { return 1 }
+			if len(foo.m) != 0 { return 1 }
+			if len(foo.b) != 0 { return 1 }
+			if len(foo.a) != 0 { return 1 }
+			s := foo.s
+			if s.ii != 0 { return 1 }
+			return 2
+		}`,
+		big.NewInt(2),
+	},
 }
 
 func TestStructs(t *testing.T) {