accounts/abi: fix index error

accounts/abi/type.go

@@ -126,7 +126,7 @@ func NewType(t string, internalType string, components []ArgumentMarshaling) (ty
 	var varSize int
 	if len(parsedType[3]) > 0 {
 		var err error
-		varSize, err = strconv.Atoi(parsedType[2])
+		varSize, err = strconv.Atoi(parsedType[3])
 		if err != nil {
 			return Type{}, fmt.Errorf("abi: error parsing variable size: %v", err)
 		}

accounts/abi/type_test.go

@@ -19,6 +19,7 @@ package abi
 import (
 	"math/big"
 	"reflect"
+	"strings"
 	"testing"
 
 	"github.com/davecgh/go-spew/spew"
@@ -378,3 +379,22 @@ func TestNewFixedBytesOver32(t *testing.T) {
 		t.Errorf("fixed bytes with size over 32 is not spec'd")
 	}
 }
+
+// TestNewTypeFixedPointWrongSizeSubmatch is a regression test for a bug in NewType
+// that used the wrong regexp submatch (parsedType[2]) for the first numeric size.
+// For types like fixed128x18, the overall second group is "128x18", not an integer
+// string; the first integer is parsedType[3] ("128"). The bug caused strconv.Atoi
+// to fail with "error parsing variable size" instead of the intended "unsupported
+// arg type" outcome for unimplemented fixed-point encodings.
+func TestNewTypeFixedPointWrongSizeSubmatch(t *testing.T) {
+	t.Parallel()
+	for _, s := range []string{"fixed128x18", "ufixed256x10"} {
+		_, err := NewType(s, "", nil)
+		if err == nil {
+			t.Fatalf("type %q: expected error for unsupported fixed-point type", s)
+		}
+		if strings.Contains(err.Error(), "error parsing variable size") {
+			t.Fatalf("type %q: got size parse error (wrong regexp submatch); want unsupported: %v", s, err)
+		}
+	}
+}