compiler: support pointer dereferencing for structs

Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>

pkg/compiler/codegen.go

@@ -610,6 +610,16 @@ func (c *codegen) Visit(node ast.Node) ast.Visitor {
 		c.emitLoadConst(c.typeAndValueOf(n))
 		return nil
 
+	case *ast.StarExpr:
+		_, ok := c.getStruct(c.typeOf(n.X))
+		if !ok {
+			c.prog.Err = errors.New("dereferencing is only supported on structs")
+			return nil
+		}
+		ast.Walk(c, n.X)
+		c.emitConvert(stackitem.StructT)
+		return nil
+
 	case *ast.Ident:
 		if tv := c.typeAndValueOf(n); tv.Value != nil {
 			c.emitLoadConst(tv)

pkg/compiler/pointer_test.go

@@ -16,3 +16,15 @@ func TestAddressOfLiteral(t *testing.T) {
 	func setA(s *Foo, a int) { s.A = a }`
 	eval(t, src, big.NewInt(3))
 }
+
+func TestPointerDereference(t *testing.T) {
+	src := `package foo
+	type Foo struct { A int	}
+	func Main() int {
+		f := &Foo{A: 4}
+		setA(*f, 3)
+		return f.A
+	}
+	func setA(s Foo, a int) { s.A = a }`
+	eval(t, src, big.NewInt(4))
+}