fix(gnolang): reject invalid undefined/nil type conversions

gnovm/pkg/gnolang/values_conversions.go

@@ -77,8 +77,10 @@ GNO_CASE:
 	}
 	// special case for undefined/nil source
 	if tv.IsUndefined() {
-		tv.T = t
-		return
+		panic(fmt.Sprintf(
+			"cannot convert %s (untyped %s constant) to type %s",
+			tv.String(), tv.T.String(), t.String()),
+		)
 	}
 	// general case
 	tvk := tv.T.Kind()

gnovm/pkg/gnolang/values_conversions_test.go

@@ -23,3 +23,170 @@ func TestConvertUntypedBigdecToFloat(t *testing.T) {
 
 	require.Equal(t, float64(0), dst.GetFloat64())
 }
+
+// TODO: Can't convert int to float.
+// func TestVarDeclTypeConversionInt2Float(t *testing.T) {
+// 	m := NewMachine("test", nil)
+// 	c := `package test
+// func main() {
+// 	x := 10
+// 	println(float64(x))
+// }`
+// 	n := MustParseFile("main.go", c)
+// 	m.RunFiles(n)
+// 	m.RunMain()
+
+// 	assertOutput(t, c, "+1.000000e+001\n")
+// }
+
+func TestShortenVarDeclTypeConversion(t *testing.T) {
+	m := NewMachine("test", nil)
+	c := `package test
+func main() {
+	println(bool(nil))
+}`
+	n := MustParseFile("main.go", c)
+	defer func() {
+		if r := recover(); r == nil {
+			t.Errorf("The code did not panic")
+		}
+	}()
+	m.RunFiles(n)
+	m.RunMain()
+
+	if err := m.CheckEmpty(); err != nil {
+		t.Error(err)
+	}
+}
+
+type testConversion struct {
+	name     string
+	src      string
+	expected string
+}
+
+func TestVariableTypeConversion(t *testing.T) {
+	tests := []testConversion{
+		{
+			name: "float to int",
+			src: `package test
+			func main() {
+				var x float64 = 10.5
+				println(int(x))
+			}`,
+			expected: "10\n",
+		},
+		{
+			name: "float to int with short declaration",
+			src: `package test
+			func main() {
+				x := 10.5
+				println(int(x))
+			}`,
+			expected: "10\n",
+		},
+		{
+			name: "eval expr to int",
+			src: `package test
+			func main() {
+				x := 10 / 3
+				println(int(x))
+			}`,
+			expected: "3\n",
+		},
+	}
+
+	for _, test := range tests {
+		m := NewMachine("test", nil)
+		n := MustParseFile("main.go", test.src)
+		m.RunFiles(n)
+		m.RunMain()
+		assertOutput(t, test.src, test.expected)
+
+		if err := m.CheckEmpty(); err != nil {
+			t.Error(err)
+		}
+	}
+}
+
+type testConversionPanic struct {
+	name string
+	src  string
+}
+
+func TestVariableTypeConversionShouldPanic(t *testing.T) {
+	tests := []testConversionPanic{
+		{
+			name: "convert untyped float constant to int",
+			src: `package test
+			func main() {
+				println(int(10.5))
+			}`,
+		},
+		{
+			name: "convert IntKind to BoolKind",
+			src: `package test
+			func main() {
+				println(bool(1))
+			}`,
+		},
+		{
+			name: "convert eval expr to bool",
+			src: `package test
+			func main() {
+				println(bool(10 / 5))
+			}`,
+		},
+		{
+			name: "convert nil to bool",
+			src: `package test
+			func main() {
+				println(bool(nil))
+			}`,
+		},
+		{
+			name: "convert string to int",
+			src: `package test
+			func main() {
+				println(int("123"))
+			}`,
+		},
+		{
+			name: "convert bool to int",
+			src: `package test
+			func main() {
+				println(int(true))
+			}`,
+		},
+		{
+			name: "convert slice to int",
+			src: `package test
+			func main() {
+				println(int([]int{1, 2, 3}))
+			}`,
+		},
+		{
+			name: "convert map to int",
+			src: `package test
+			func main() {
+				println(int(map[string]int{"one": 1}))
+			}`,
+		},
+	}
+
+	for _, test := range tests {
+		m := NewMachine("test", nil)
+		n := MustParseFile("main.go", test.src)
+		defer func() {
+			if r := recover(); r == nil {
+				t.Errorf("The code did not panic")
+			}
+		}()
+		m.RunFiles(n)
+		m.RunMain()
+
+		if err := m.CheckEmpty(); err != nil {
+			t.Error(err)
+		}
+	}
+}