feat: named and unnamed type assignment 2 of 3 (gnolang#1246)

This is part 2 of 3 of the solution for issue gnolang#1141. The part 1 of 3 of
the solution can be found in issue gnolang#1143.

In this part of the solution, we have made several improvements:

- Support both named and unnamed type assignments in assignment
statements and function return values.
- Resolved the issue related to incorrect method selectors that is
caused by mixing named and unnamed assignments.
- Added 62 file tests to ensure the correctness of the code.
- Included 2 realm tests to further validate the cross realm assignment
and method selector.
- Enhanced the support for GNO file tests in nested directories. This
allows us to organize tests in intuitively named folders.

To achieve the above improvements in the preprocessing phase, we made
the following changes:

- Introduced an isNamed() function on the Type Interface and marked
named types with isNamed() returning true. This helps distinguish
between named and unnamed types.
- Followed the specifications to convert the right-hand side type into a
constant function type.
- As for determining the package associated with a test file, we've
maintained the original convention. We keeps relying on the comment
directive "//PKGPATH: gno.land/r/xyz" in the test file itself to
identify the package it belongs to. We do not using the local folder
structure to derive the package for file tests. Therefore the tests in
tests/files folder can be stored in any intuitively named sub
directories.

**NOTE:** The named and unnamed type conversions that involve the
decomposition of function calls returning multiple values in the
preprocess have not yet been included in this pull request. This
functionality will be addressed in part 3 of 3 of the entire solution.

<!-- please provide a detailed description of the changes made in this
pull request. -->

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

- [x] Added new tests, or not needed, or not feasible
- [ ] Provided an example (e.g. screenshot) to aid review or the PR is
self-explanatory
- [ ] Updated the official documentation or not needed
- [ ] No breaking changes were made, or a `BREAKING CHANGE: xxx` message
was included in the description
- [x] Added references to related issues and PRs
- [ ] Provided any useful hints for running manual tests
- [ ] 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>

---------

Co-authored-by: deelawn <dboltz03@gmail.com>
Co-authored-by: Morgan Bazalgette <morgan@morganbaz.com>

examples/gno.land/r/demo/tests/realm_compositelit.gno

@@ -0,0 +1,22 @@
+package tests
+
+type (
+	Word uint
+	nat  []Word
+)
+
+var zero = &Int{
+	neg: true,
+	abs: []Word{0},
+}
+
+// structLit
+type Int struct {
+	neg bool
+	abs nat
+}
+
+func GetZeroType() nat {
+	a := zero.abs
+	return a
+}

examples/gno.land/r/demo/tests/realm_method38d.gno

@@ -0,0 +1,19 @@
+package tests
+
+var abs nat
+
+func (n nat) Add() nat {
+	return []Word{0}
+}
+
+func GetAbs() nat {
+	abs = []Word{0}
+
+	return abs
+}
+
+func AbsAdd() nat {
+	rt := GetAbs().Add()
+
+	return rt
+}

gnovm/pkg/gnolang/preprocess.go

@@ -1621,8 +1621,12 @@ func Preprocess(store Store, ctx BlockNode, n Node) Node {
 							lhs0 := n.Lhs[0].(*NameExpr).Name
 							lhs1 := n.Lhs[1].(*NameExpr).Name
 
+							var mt *MapType
 							dt := evalStaticTypeOf(store, last, cx.X)
-							mt := baseOf(dt).(*MapType)
+							mt, ok := baseOf(dt).(*MapType)
+							if !ok {
+								panic(fmt.Sprintf("invalid index expression on %T", dt))
+							}
 							// re-definitions
 							last.Define(lhs0, anyValue(mt.Value))
 							last.Define(lhs1, anyValue(BoolType))
@@ -2263,12 +2267,12 @@ func getResultTypedValues(cx *CallExpr) []TypedValue {
 func evalConst(store Store, last BlockNode, x Expr) *ConstExpr {
 	// TODO: some check or verification for ensuring x
 	// is constant?  From the machine?
-	cv := NewMachine(".dontcare", store)
-	tv := cv.EvalStatic(last, x)
-	cv.Release()
+	m := NewMachine(".dontcare", store)
+	cv := m.EvalStatic(last, x)
+	m.Release()
 	cx := &ConstExpr{
 		Source:     x,
-		TypedValue: tv,
+		TypedValue: cv,
 	}
 	cx.SetAttribute(ATTR_PREPROCESSED, true)
 	setConstAttrs(cx)
@@ -2465,11 +2469,13 @@ func checkOrConvertType(store Store, last BlockNode, x *Expr, t Type, autoNative
 		// "push" expected type into shift binary's left operand.
 		checkOrConvertType(store, last, &bx.Left, t, autoNative)
 	} else if *x != nil { // XXX if x != nil && t != nil {
+		// check type
 		xt := evalStaticTypeOf(store, last, *x)
 		if t != nil {
 			checkType(xt, t, autoNative)
 		}
-		if isUntyped(xt) {
+		// convert type
+		if isUntyped(xt) { // convert if x is untyped literal
 			if t == nil {
 				t = defaultTypeOf(xt)
 			}
@@ -2490,11 +2496,61 @@ func checkOrConvertType(store Store, last BlockNode, x *Expr, t Type, autoNative
 					// default:
 				}
 			}
-			cx := Expr(Call(constType(nil, t), *x))
-			cx = Preprocess(store, last, cx).(Expr)
-			*x = cx
+			// convert x to destination type t
+			convertType(store, last, x, t)
+		} else {
+			// if one side is declared name type and the other side is unnamed type
+			if isNamedConversion(xt, t) {
+				// covert right (xt) to the type of the left (t)
+				convertType(store, last, x, t)
+			}
+		}
+	}
+}
+
+// convert x to destination type t
+func convertType(store Store, last BlockNode, x *Expr, t Type) {
+	cx := Expr(Call(constType(nil, t), *x))
+	cx = Preprocess(store, last, cx).(Expr)
+	*x = cx
+}
+
+// isNamedConversion returns true if assigning a value of type
+// xt (rhs) into a value of type t (lhs) entails an implicit type conversion.
+// xt is the result of an expression type.
+//
+// In a few special cases, we should not perform the conversion:
+//
+//	case 1: the LHS is an interface, which is unnamed, so we should not
+//	convert to that even if right is a named type.
+//	case 2: isNamedConversion is called within evaluating make() or new()
+//	(uverse functions). It returns TypType (generic) which does have IsNamed appropriate
+func isNamedConversion(xt, t Type) bool {
+	if t == nil {
+		t = xt
+	}
+
+	// no conversion case 1: the LHS is an interface
+
+	_, c1 := t.(*InterfaceType)
+
+	// no conversion case2: isNamedConversion is called within evaluating make() or new()
+	//   (uverse functions)
+
+	_, oktt := t.(*TypeType)
+	_, oktt2 := xt.(*TypeType)
+	c2 := oktt || oktt2
+
+	//
+	if !c1 && !c2 { // carve out above two cases
+		// covert right to the type of left if one side is unnamed type and the other side is not
+
+		if t.IsNamed() && !xt.IsNamed() ||
+			!t.IsNamed() && xt.IsNamed() {
+			return true
 		}
 	}
+	return false
 }
 
 // like checkOrConvertType(last, x, nil)

gnovm/pkg/gnolang/types.go

@@ -24,6 +24,7 @@ type Type interface {
 	String() string // for dev/debugging
 	Elem() Type     // for TODO... types
 	GetPkgPath() string
+	IsNamed() bool // named vs unname type. property as a method
 }
 
 type TypeID string
@@ -323,6 +324,10 @@ func (pt PrimitiveType) GetPkgPath() string {
 	return ""
 }
 
+func (pt PrimitiveType) IsNamed() bool {
+	return true
+}
+
 // ----------------------------------------
 // Field type (partial)
 
@@ -369,6 +374,10 @@ func (ft FieldType) GetPkgPath() string {
 	panic("FieldType is a pseudotype with no package path")
 }
 
+func (ft FieldType) IsNamed() bool {
+	panic("FieldType is a pseudotype with no property called named")
+}
+
 // ----------------------------------------
 // FieldTypeList
 
@@ -528,6 +537,10 @@ func (at *ArrayType) GetPkgPath() string {
 	return ""
 }
 
+func (at *ArrayType) IsNamed() bool {
+	return false
+}
+
 // ----------------------------------------
 // Slice type
 
@@ -574,6 +587,10 @@ func (st *SliceType) GetPkgPath() string {
 	return ""
 }
 
+func (st *SliceType) IsNamed() bool {
+	return false
+}
+
 // ----------------------------------------
 // Pointer type
 
@@ -612,6 +629,10 @@ func (pt *PointerType) GetPkgPath() string {
 	return pt.Elt.GetPkgPath()
 }
 
+func (pt *PointerType) IsNamed() bool {
+	return false
+}
+
 func (pt *PointerType) FindEmbeddedFieldType(callerPath string, n Name, m map[Type]struct{}) (
 	trail []ValuePath, hasPtr bool, rcvr Type, field Type, accessError bool,
 ) {
@@ -747,6 +768,10 @@ func (st *StructType) GetPkgPath() string {
 	return st.PkgPath
 }
 
+func (st *StructType) IsNamed() bool {
+	return false
+}
+
 // NOTE only works for exposed non-embedded fields.
 func (st *StructType) GetPathForName(n Name) ValuePath {
 	for i := 0; i < len(st.Fields); i++ {
@@ -867,6 +892,10 @@ func (pt *PackageType) GetPkgPath() string {
 	panic("package types has no package path (unlike package values)")
 }
 
+func (pt *PackageType) IsNamed() bool {
+	panic("package types have no property called named")
+}
+
 // ----------------------------------------
 // Interface type
 
@@ -926,6 +955,10 @@ func (it *InterfaceType) GetPkgPath() string {
 	return it.PkgPath
 }
 
+func (it *InterfaceType) IsNamed() bool {
+	return false
+}
+
 func (it *InterfaceType) FindEmbeddedFieldType(callerPath string, n Name, m map[Type]struct{}) (
 	trail []ValuePath, hasPtr bool, rcvr Type, ft Type, accessError bool,
 ) {
@@ -1073,6 +1106,10 @@ func (ct *ChanType) GetPkgPath() string {
 	return ""
 }
 
+func (ct *ChanType) IsNamed() bool {
+	return false
+}
+
 // ----------------------------------------
 // Function type
 
@@ -1280,6 +1317,10 @@ func (ft *FuncType) GetPkgPath() string {
 	panic("function types have no package path")
 }
 
+func (ft *FuncType) IsNamed() bool {
+	return false
+}
+
 func (ft *FuncType) HasVarg() bool {
 	if numParams := len(ft.Params); numParams == 0 {
 		return false
@@ -1338,6 +1379,10 @@ func (mt *MapType) GetPkgPath() string {
 	return ""
 }
 
+func (mt *MapType) IsNamed() bool {
+	return false
+}
+
 // ----------------------------------------
 // Type (typeval) type
 
@@ -1366,6 +1411,10 @@ func (tt *TypeType) GetPkgPath() string {
 	panic("typeval types have no package path")
 }
 
+func (tt *TypeType) IsNamed() bool {
+	panic("typeval types have no property called 'named'")
+}
+
 // ----------------------------------------
 // Declared type
 // Declared types have a name, base (underlying) type,
@@ -1450,6 +1499,10 @@ func (dt *DeclaredType) GetPkgPath() string {
 	return dt.PkgPath
 }
 
+func (dt *DeclaredType) IsNamed() bool {
+	return true
+}
+
 func (dt *DeclaredType) DefineMethod(fv *FuncValue) {
 	if !dt.TryDefineMethod(fv) {
 		panic(fmt.Sprintf("redeclaration of method %s.%s",
@@ -1767,6 +1820,14 @@ func (nt *NativeType) GetPkgPath() string {
 	return "go:" + nt.Type.PkgPath()
 }
 
+func (nt *NativeType) IsNamed() bool {
+	if nt.Type.Name() != "" {
+		return true
+	} else {
+		return false
+	}
+}
+
 func (nt *NativeType) GnoType(store Store) Type {
 	if nt.gnoType == nil {
 		nt.gnoType = store.Go2GnoType(nt.Type)
@@ -1895,6 +1956,10 @@ func (bt blockType) GetPkgPath() string {
 	panic("blockType has no package path")
 }
 
+func (bt blockType) IsNamed() bool {
+	panic("blockType has no property called named")
+}
+
 // ----------------------------------------
 // tupleType
 
@@ -1945,6 +2010,10 @@ func (tt *tupleType) GetPkgPath() string {
 	panic("typleType has no package path")
 }
 
+func (tt *tupleType) IsNamed() bool {
+	panic("typleType has no property called named")
+}
+
 // ----------------------------------------
 // RefType
 
@@ -1965,11 +2034,15 @@ func (rt RefType) String() string {
 }
 
 func (rt RefType) Elem() Type {
-	panic("should not happen")
+	panic("RefType has no elem type")
 }
 
 func (rt RefType) GetPkgPath() string {
-	panic("should not happen")
+	panic("RefType has no package path")
+}
+
+func (rt RefType) IsNamed() bool {
+	panic("RefType has no property called named")
 }
 
 // ----------------------------------------
@@ -2002,6 +2075,10 @@ func (mn MaybeNativeType) GetPkgPath() string {
 	return mn.Type.GetPkgPath()
 }
 
+func (mn MaybeNativeType) IsNamed() bool {
+	return mn.Type.IsNamed()
+}
+
 // ----------------------------------------
 // Kind
 

gnovm/pkg/gnolang/uverse_test.go

@@ -39,7 +39,7 @@ func TestIssue1337PrintNilSliceAsUndefined(t *testing.T) {
 				var a []string
 				println(a)
 			}`,
-			expected: "nil []string\n",
+			expected: "(nil []string)\n",
 		},
 		{
 			name: "print non-empty slice",
@@ -57,7 +57,7 @@ func TestIssue1337PrintNilSliceAsUndefined(t *testing.T) {
 				var a map[string]string
 				println(a)
 			}`,
-			expected: "nil map[string]string\n",
+			expected: "(nil map[string]string)\n",
 		},
 		{
 			name: "print non-empty map",

gnovm/pkg/gnolang/values_string.go

@@ -376,7 +376,7 @@ func (tv *TypedValue) ProtectedSprint(seen *seenValues, considerDeclaredType boo
 	default:
 		// The remaining types may have a nil value.
 		if tv.V == nil {
-			return nilStr + " " + tv.T.String()
+			return "(" + nilStr + " " + tv.T.String() + ")"
 		}
 
 		// *ArrayType, *SliceType, *StructType, *MapType