decimal: remove error from Pad method

CHANGELOG.md

@@ -1,6 +1,6 @@
 # Changelog
 
-## [0.1.26] - 2024-05-19
+## [0.1.27] - 2024-05-19
 
 ### Changed
 

decimal.go

@@ -100,7 +100,7 @@ func newFromBint(neg bool, coef *bint, scale, minScale int) (Decimal, error) {
 		scale = MaxScale
 	case prec > scale && prec > MaxPrec: // there is an integer part
 		coef.rshHalfEven(coef, prec-MaxPrec)
-		scale = scale - (prec - MaxPrec)
+		scale = MaxPrec - prec + scale
 	}
 	// Handling the rare case when rshHalfEven rounded
 	// a 19-digit coefficient to a 20-digit coefficient.
@@ -1018,7 +1018,7 @@ func (d Decimal) Round(scale int) Decimal {
 // The total number of digits in the result is limited by [MaxPrec].
 // See also method [Decimal.Trim].
 func (d Decimal) Pad(scale int) Decimal {
-	scale = min(scale, MaxPrec-d.Prec()+d.Scale())
+	scale = min(scale, MaxScale, MaxPrec-d.Prec()+d.Scale())
 	if scale <= d.Scale() {
 		return d
 	}

decimal_test.go

@@ -1241,12 +1241,12 @@ func TestDecimal_Pad(t *testing.T) {
 		{"0", 1, "0.0"},
 		{"0", 2, "0.00"},
 		{"0", 19, "0.0000000000000000000"},
-		{"0.0", 1, "0.0"},
-		{"0.00", 2, "0.00"},
-		{"0.000000000", 19, "0.0000000000000000000"},
+		{"0", 20, "0.0000000000000000000"},
 		{"0.000000000", 0, "0.000000000"},
 		{"0.000000000", 1, "0.000000000"},
 		{"0.000000000", 2, "0.000000000"},
+		{"0.000000000", 19, "0.0000000000000000000"},
+		{"0.000000000", 20, "0.0000000000000000000"},
 
 		// Tests from GDA
 		{"2.17", 0, "2.17"},
@@ -1272,7 +1272,7 @@ func TestDecimal_Pad(t *testing.T) {
 		{"100000000000000", 5, "100000000000000.0000"},
 		{"10000000000000", 6, "10000000000000.00000"},
 		{"1000000000000", 7, "1000000000000.000000"},
-		{"0", 20, "0.0000000000000000000"},
+		{"-0.0000000000032", 63, "-0.0000000000032000000"},
 	}
 	for _, tt := range tests {
 		d := MustParse(tt.d)
@@ -3526,6 +3526,11 @@ func FuzzDecimal_Pad(f *testing.F) {
 			got := want.Pad(scale)
 			if got.Cmp(want) != 0 {
 				t.Errorf("%q.Pad(%v) = %q", want, scale, got)
+				return
+			}
+			if got.Scale() > MaxScale {
+				t.Errorf("%q.Pad(%v).Scale() = %v", want, scale, got.Scale())
+				return
 			}
 		},
 	)