compiler: allow to omit struct field names in literals

pkg/compiler/codegen.go

@@ -1253,12 +1253,25 @@ func (c *codegen) convertStruct(lit *ast.CompositeLit) {
 	emit.Int(c.prog.BinWriter, int64(strct.NumFields()))
 	emit.Opcode(c.prog.BinWriter, opcode.NEWSTRUCT)
 
+	keyedLit := len(lit.Elts) > 0
+	if keyedLit {
+		_, ok := lit.Elts[0].(*ast.KeyValueExpr)
+		keyedLit = keyedLit && ok
+	}
 	// We need to locally store all the fields, even if they are not initialized.
 	// We will initialize all fields to their "zero" value.
 	for i := 0; i < strct.NumFields(); i++ {
 		sField := strct.Field(i)
 		fieldAdded := false
 
+		if !keyedLit {
+			emit.Opcode(c.prog.BinWriter, opcode.DUP)
+			emit.Int(c.prog.BinWriter, int64(i))
+			ast.Walk(c, lit.Elts[i])
+			emit.Opcode(c.prog.BinWriter, opcode.SETITEM)
+			continue
+		}
+
 		// Fields initialized by the program.
 		for _, field := range lit.Elts {
 			f := field.(*ast.KeyValueExpr)

pkg/compiler/struct_test.go

@@ -394,6 +394,17 @@ var structTestCases = []testCase{
 		}`,
 		big.NewInt(42),
 	},
+	{
+		"omit field names",
+		`package foo
+		type pair struct { a, b int }
+		func Main() int {
+			p := pair{1, 2}
+			x := p.a * 10
+			return x + p.b
+		}`,
+		big.NewInt(12),
+	},
 }
 
 func TestStructs(t *testing.T) {