launchpad: backport BigInt fix (#7087)

Backported from #7084

Co-authored-by: Alessio Treglia <alessio@tendermint.com>

CHANGELOG.md

@@ -35,6 +35,12 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 # Changelog
 
+## [v0.39.2]
+
+### Bug Fixes
+
+* (types) [\#7084](https://github.com/cosmos/cosmos-sdk/pull/7084) Fix panic when calling `BigInt()` on an uninitialized `Int`.
+
 ## [v0.39.1]
 
 * (x/auth) [\#6861](https://github.com/cosmos/cosmos-sdk/pull/6861) Remove public key Bech32 encoding for all account types for JSON serialization, instead relying on direct Amino encoding. In addition, JSON serialization utilizes Amino instead of the Go stdlib, so integers are treated as strings.

types/decimal.go

@@ -205,6 +205,16 @@ func (d Dec) LTE(d2 Dec) bool   { return (d.Int).Cmp(d2.Int) <= 0 }     // less
 func (d Dec) Neg() Dec          { return Dec{new(big.Int).Neg(d.Int)} } // reverse the decimal sign
 func (d Dec) Abs() Dec          { return Dec{new(big.Int).Abs(d.Int)} } // absolute value
 
+// BigInt returns a copy of the underlying big.Int.
+func (d Dec) BigInt() *big.Int {
+	if d.IsNil() {
+		return nil
+	}
+
+	copy := new(big.Int)
+	return copy.Set(d.Int)
+}
+
 // addition
 func (d Dec) Add(d2 Dec) Dec {
 	res := new(big.Int).Add(d.Int, d2.Int)

types/int.go

@@ -106,9 +106,17 @@ type Int struct {
 
 // BigInt converts Int to big.Int
 func (i Int) BigInt() *big.Int {
+	if i.IsNil() {
+		return nil
+	}
 	return new(big.Int).Set(i.i)
 }
 
+// IsNil returns true if Int is uninitialized
+func (i Int) IsNil() bool {
+	return i.i == nil
+}
+
 // NewInt constructs Int from int64
 func NewInt(n int64) Int {
 	return Int{big.NewInt(n)}

types/int_test.go

@@ -78,6 +78,8 @@ func TestIntPanic(t *testing.T) {
 
 	// Division-by-zero check
 	require.Panics(t, func() { i1.Quo(NewInt(0)) })
+
+	require.NotPanics(t, func() { Int{}.BigInt() })
 }
 
 // Tests below uses randomness