feat(gnovm): align Gno constant handling with Go specifications

gnovm/pkg/gnolang/preprocess.go

@@ -2188,6 +2188,7 @@ func Preprocess(store Store, ctx BlockNode, n Node) Node {
 					// NOTE: may or may not be a *ConstExpr,
 					// but if not, make one now.
 					for i, vx := range n.Values {
+						checkConstantExpr(store, last, vx)
 						n.Values[i] = evalConst(store, last, vx)
 					}
 				} else {
@@ -2268,6 +2269,12 @@ func Preprocess(store Store, ctx BlockNode, n Node) Node {
 					if n.Type != nil {
 						// only a single type can be specified.
 						nt := evalStaticType(store, last, n.Type)
+						if n.Const {
+							if _, ok := baseOf(nt).(PrimitiveType); !ok {
+								panic(fmt.Sprintf("invalid constant type %s", nt.String()))
+							}
+						}
+
 						for i := 0; i < numNames; i++ {
 							sts[i] = nt
 						}
@@ -2279,6 +2286,9 @@ func Preprocess(store Store, ctx BlockNode, n Node) Node {
 						// derive static type from values.
 						for i, vx := range n.Values {
 							vt := evalStaticTypeOf(store, last, vx)
+							if _, ok := baseOf(vt).(PrimitiveType); !ok {
+								panic(fmt.Sprintf("%s (value of type %s) is not constant", vx.String(), vt.String()))
+							}
 							sts[i] = vt
 						}
 					} else {

gnovm/pkg/gnolang/type_check.go

@@ -215,6 +215,72 @@ func assertAssignableTo(xt, dt Type, autoNative bool) {
 	}
 }
 
+func checkConstantExpr(store Store, last BlockNode, vx Expr) {
+Main:
+	switch vx := vx.(type) {
+	case *NameExpr:
+		panic(fmt.Sprintf("%s (variable of type %s) is not constant", vx.Name, evalStaticTypeOf(store, last, vx)))
+	case *TypeAssertExpr:
+		panic(fmt.Sprintf("%s (comma, ok expression of type %s) is not constant", vx.String(), vx.Type))
+	case *IndexExpr:
+		panic(fmt.Sprintf("%s (variable of type %s) is not constant", vx.String(), vx.X))
+	case *CallExpr:
+		ift := evalStaticTypeOf(store, last, vx.Func)
+		tup := evalStaticTypeOfRaw(store, last, vx).(*tupleType)
+		switch baseOf(ift).(type) {
+		case *FuncType:
+
+			// check for built-in functions
+			if cx, ok := vx.Func.(*ConstExpr); ok {
+				if fv, ok := cx.V.(*FuncValue); ok {
+					if fv.PkgPath == uversePkgPath {
+						switch {
+						case fv.Name == "len":
+							checkConstantExpr(store, last, vx.Args[0])
+							break Main
+						case fv.Name == "min":
+							checkConstantExpr(store, last, vx.Args[0])
+							checkConstantExpr(store, last, vx.Args[1])
+							break Main
+						case fv.Name == "max":
+							checkConstantExpr(store, last, vx.Args[0])
+							checkConstantExpr(store, last, vx.Args[1])
+							break Main
+						}
+					}
+				}
+			}
+
+			switch {
+			case len(tup.Elts) == 0:
+				panic(fmt.Sprintf("%s (no value) used as value", vx.String()))
+			case len(tup.Elts) == 1:
+				panic(fmt.Sprintf("%s (value of type %s) is not constant", vx.String(), tup.Elts[0]))
+			default:
+				panic(fmt.Sprintf("multiple-value %s (value of type %s) in single-value context", vx.String(), tup.Elts))
+			}
+		case *TypeType:
+			fmt.Printf("TypeType\n")
+		case *NativeType:
+			fmt.Printf("NativeType\n")
+		default:
+			fmt.Printf("ValueDecl: %T\n", vx)
+			panic(fmt.Sprintf(
+				"unexpected func type %v (%v)",
+				ift, reflect.TypeOf(ift)))
+		}
+	case *BinaryExpr:
+		checkConstantExpr(store, last, vx.Left)
+		checkConstantExpr(store, last, vx.Right)
+	case *ConstExpr:
+	case *BasicLitExpr:
+	default:
+		ift := evalStaticTypeOf(store, last, vx)
+		panic(fmt.Sprintf("%s (variable of type %s) is not constant", vx.String(), ift))
+
+	}
+}
+
 // checkValDefineMismatch checks for mismatch between the number of variables and values in a ValueDecl or AssignStmt.
 func checkValDefineMismatch(n Node) {
 	var (

gnovm/tests/files/const23.gno

@@ -0,0 +1,11 @@
+package main
+
+import "fmt"
+
+func main() {
+	const t []string = []string{}
+	fmt.Println(t)
+}
+
+// Error:
+// main/files/const23.gno:6:8: invalid constant type []string

gnovm/tests/files/const24.gno

@@ -0,0 +1,67 @@
+package main
+
+import "fmt"
+
+func main() {
+	const a int = 1_000_000
+	const b byte = byte(1)
+	const c float64 = 1_000_000.000
+	const d string = "Hello, World!"
+	const e rune = 'a'
+	const g bool = true
+	const h uint = 1_000
+	const i int8 = 1
+	const j int16 = 1
+	const k int32 = 1
+	const l int64 = 1
+	const m uint8 = 1
+	const n uint16 = 1
+	const o uint32 = 1
+	const p uint64 = 1
+	const r float32 = 1_000_000.000
+	const s = r
+	const t = len("s")
+	const u = min(i, min(1, 3))
+	const v = max(i, max(1, 3))
+	const w = min(i, max(1, 3)) + max(i, min(1, 3)) + 3
+	const x+=w
+
+	fmt.Println(a)
+	fmt.Println(b)
+	fmt.Println(c)
+	fmt.Println(d)
+	fmt.Println(e)
+	fmt.Println(g)
+	fmt.Println(h)
+	fmt.Println(i)
+	fmt.Println(j)
+	fmt.Println(k)
+	fmt.Println(l)
+	fmt.Println(m)
+	fmt.Println(n)
+	fmt.Println(o)
+	fmt.Println(p)
+	fmt.Println(r)
+	fmt.Println(s)
+	fmt.Println(t)
+}
+
+// Output:
+// 1000000
+// 1
+// 1e+06
+// Hello, World!
+// 97
+// true
+// 1000
+// 1
+// 1
+// 1
+// 1
+// 1
+// 1
+// 1
+// 1
+// 1e+06
+// 1e+06
+// 1

gnovm/tests/files/const25.gno

@@ -0,0 +1,11 @@
+package main
+
+import "fmt"
+
+func main() {
+	const t = []string{"1"}
+	fmt.Println(t)
+}
+
+// Error:
+// main/files/const25.gno:6:8: (const (slice[("1" string)] []string)) (value of type []string) is not constant

gnovm/tests/files/const26.gno

@@ -0,0 +1,15 @@
+package main
+
+import "fmt"
+
+func v() string {
+	return ""
+}
+
+func main() {
+	const t = v()
+	fmt.Println(t)
+}
+
+// Error:
+// main/files/const25.gno:6:8: (const (slice[("1" string)] []string)) (value of type []string) is not constant

gnovm/tests/files/const27.gno

@@ -0,0 +1,16 @@
+package main
+
+import "fmt"
+
+func v() string {
+	return ""
+}
+
+func main() {
+	var i interface{} = 1
+	const t, ok = i.(int)
+	fmt.Println(t, ok)
+}
+
+// Error:
+// main/files/const27.gno:11:8: i<VPUverse(0)>.(int<VPUverse(0)>) (comma, ok expression of type int<VPUverse(0)>) is not constant

gnovm/tests/files/const28.gno

@@ -0,0 +1,12 @@
+package main
+
+import "fmt"
+
+func main() {
+	var s []string = []string{"1"}
+	const t, ok = s[0]
+	fmt.Println(t, ok)
+}
+
+// Error:
+// main/files/const25.gno:6:8: (const (slice[("1" string)] []string)) (value of type []string) is not constant

gnovm/tests/files/const29.gno

@@ -0,0 +1,12 @@
+package main
+
+import "fmt"
+
+func main() {
+	s := "1"
+	const t = s
+	fmt.Println(t)
+}
+
+// Error:
+// main/files/const29.gno:7:8: s (variable of type string) is not constant

gnovm/tests/files/const30.gno

@@ -0,0 +1,15 @@
+package main
+
+import "fmt"
+
+func v() {
+	return
+}
+
+func main() {
+	const t = v()
+	fmt.Println(t)
+}
+
+// Error:
+// main/files/const29.gno:7:8: s (variable of type string) is not constant

gnovm/tests/files/const31.gno

@@ -0,0 +1,15 @@
+package main
+
+import "fmt"
+
+func v() (string, string) {
+	return "", ""
+}
+
+func main() {
+	const t, v = v()
+	fmt.Println(t)
+}
+
+// Error:
+// main/files/const29.gno:7:8: s (variable of type string) is not constant