fix: allow constant values of infininitesimal non-zero floating points (

gnolang#1185)

Added a unit test and an integration test trying to reproduce gnolang#1150 

Avoid unhandled errors.

- [x] Added new tests, or not needed, or not feasible
- [x] Provided an example (e.g. screenshot) to aid review or the PR is
self-explanatory
- [x] Updated the official documentation or not needed
- [x] No breaking changes were made, or a `BREAKING CHANGE: xxx` message
was included in the description
- [x] Added references to related issues and PRs
- [x] Provided any useful hints for running manual tests
- [x] Added new benchmarks to [generated
graphs](https://gnoland.github.io/benchmarks), if any. More info
[here](https://github.com/gnolang/gno/blob/master/.benchmarks/README.md).

---------

Signed-off-by: Antonio Navarro Perez <antnavper@gmail.com>
Co-authored-by: Morgan Bazalgette <morgan@morganbaz.com>

gnovm/pkg/gnolang/values_conversions.go

@@ -1240,23 +1240,26 @@ func ConvertUntypedBigdecTo(dst *TypedValue, bv BigdecValue, t Type) {
 	case Float32Kind:
 		dst.T = t
 		dst.V = nil
-		f64, _ := bd.Float64()
+		f64, err := bd.Float64()
+		if err != nil {
+			panic(fmt.Errorf("cannot convert untyped bigdec to float64: %w", err))
+		}
+
 		bf := big.NewFloat(f64)
-		f32, acc := bf.Float32()
-		if f32 == 0 && (acc == big.Below || acc == big.Above) {
-			panic("cannot convert untyped bigdec to float32 -- too close to zero")
-		} else if math.IsInf(float64(f32), 0) {
+		f32, _ := bf.Float32()
+		if math.IsInf(float64(f32), 0) {
 			panic("cannot convert untyped bigdec to float32 -- too close to +-Inf")
 		}
 		dst.SetFloat32(f32)
 		return
 	case Float64Kind:
 		dst.T = t
 		dst.V = nil
-		f64, _ := bd.Float64()
-		if f64 == 0 && !bd.IsZero() {
-			panic("cannot convert untyped bigdec to float64 -- too close to zero")
-		} else if math.IsInf(f64, 0) {
+		f64, err := bd.Float64()
+		if err != nil {
+			panic(fmt.Errorf("cannot convert untyped bigdec to float64: %w", err))
+		}
+		if math.IsInf(f64, 0) {
 			panic("cannot convert untyped bigdec to float64 -- too close to +-Inf")
 		}
 		dst.SetFloat64(f64)

gnovm/pkg/gnolang/values_conversions_test.go

@@ -0,0 +1,25 @@
+package gnolang
+
+import (
+	"math"
+	"testing"
+
+	"github.com/cockroachdb/apd"
+	"github.com/stretchr/testify/require"
+)
+
+func TestConvertUntypedBigdecToFloat(t *testing.T) {
+	dst := &TypedValue{}
+
+	dec, err := apd.New(-math.MaxInt64, -4).SetFloat64(math.SmallestNonzeroFloat64 / 2)
+	require.NoError(t, err)
+	bd := BigdecValue{
+		V: dec,
+	}
+
+	typ := Float64Type
+
+	ConvertUntypedBigdecTo(dst, bd, typ)
+
+	require.Equal(t, float64(0), dst.GetFloat64())
+}

gnovm/tests/files/float6.gno

@@ -0,0 +1,13 @@
+package main
+
+const (
+	SmallestNonzeroFloat64 = 0x1p-1022 * 0x1p-52 // 4.9406564584124654417656879286822137236505980e-324
+	DividedByTwo           = SmallestNonzeroFloat64 / 2
+)
+
+func main() {
+	println(DividedByTwo)
+}
+
+// Output:
+// 0

gnovm/tests/files/float7.gno

@@ -0,0 +1,15 @@
+package main
+
+const (
+	SmallestNonzeroFloat32 = 0x1p-126 * 0x1p-23 // 1.401298464324817070923729583289916131280e-45
+	DividedByTwo           = SmallestNonzeroFloat32 / 2
+)
+
+func main() {
+	var i float32
+	i = DividedByTwo
+	println(i)
+}
+
+// Output:
+// 0