fix(gnovm): fix max names in block check (#2645)

I noticed this while reviewing #2429. The previous conditional could
never evaluate to true: `if (1<<16 - 1) < sb.NumNames {`. `sb.NumNames`
is a `uint16` and the value it is being compared to, `1<<16 - 1` is the
max uint16 value, so it is impossible the the number of names to be
greater than this value. Instead, we should check to see if the current
number of names is the maximum value and panic if this is the case.

<details><summary>Contributors' checklist...</summary>

- [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).
</details>

gnovm/pkg/gnolang/nodes.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"go/parser"
 	"go/token"
+	"math"
 	"os"
 	"path/filepath"
 	"reflect"
@@ -1802,7 +1803,7 @@ func (sb *StaticBlock) Define2(isConst bool, n Name, st Type, tv TypedValue) {
 	if int(sb.NumNames) != len(sb.Names) {
 		panic("StaticBlock.NumNames and len(.Names) mismatch")
 	}
-	if (1<<16 - 1) < sb.NumNames {
+	if sb.NumNames == math.MaxUint16 {
 		panic("too many variables in block")
 	}
 	if tv.T == nil && tv.V != nil {

gnovm/pkg/gnolang/nodes_test.go

@@ -0,0 +1,44 @@
+package gnolang_test
+
+import (
+	"math"
+	"testing"
+
+	"github.com/gnolang/gno/gnovm/pkg/gnolang"
+)
+
+func TestStaticBlock_Define2_MaxNames(t *testing.T) {
+	defer func() {
+		if r := recover(); r != nil {
+			panicString, ok := r.(string)
+			if !ok {
+				t.Errorf("expected panic string, got %v", r)
+			}
+
+			if panicString != "too many variables in block" {
+				t.Errorf("expected panic string to be 'too many variables in block', got '%s'", panicString)
+			}
+
+			return
+		}
+
+		// If it didn't panic, fail.
+		t.Errorf("expected panic when exceeding maximum number of names")
+	}()
+
+	staticBlock := new(gnolang.StaticBlock)
+	staticBlock.NumNames = math.MaxUint16 - 1
+	staticBlock.Names = make([]gnolang.Name, staticBlock.NumNames)
+
+	// Adding one more is okay.
+	staticBlock.Define2(false, gnolang.Name("a"), gnolang.BoolType, gnolang.TypedValue{T: gnolang.BoolType})
+	if staticBlock.NumNames != math.MaxUint16 {
+		t.Errorf("expected NumNames to be %d, got %d", math.MaxUint16, staticBlock.NumNames)
+	}
+	if len(staticBlock.Names) != math.MaxUint16 {
+		t.Errorf("expected len(Names) to be %d, got %d", math.MaxUint16, len(staticBlock.Names))
+	}
+
+	// This one should panic because the maximum number of names has been reached.
+	staticBlock.Define2(false, gnolang.Name("a"), gnolang.BoolType, gnolang.TypedValue{T: gnolang.BoolType})
+}