V: fix const bugs and pass const_test.v (#4206)

* fix const bug in v2

* v2: fix const decl

* small comment fix

vlib/v/ast/ast.v

@@ -110,6 +110,7 @@ mut:
 
 pub struct ConstDecl {
 pub:
+	pos    token.Position
 	fields []Field
 	exprs  []Expr
 	is_pub bool

vlib/v/checker/checker.v

@@ -150,6 +150,10 @@ pub fn (c mut Checker) infix_expr(infix_expr mut ast.InfixExpr) table.Type {
 		if right.kind in [.array, .map] && infix_expr.op == .key_in {
 			return table.bool_type
 		}
+		// fot type-unresolved consts
+		if left_type == table.void_type || right_type == table.void_type {
+			return table.void_type
+		}
 		c.error('infix expr: cannot use `$right.name` (right) as `$left.name`', infix_expr.pos)
 	}
 	if infix_expr.op.is_relational() {
@@ -346,7 +350,6 @@ pub fn (c mut Checker) call_expr(call_expr mut ast.CallExpr) table.Type {
 				if arg_typ_sym.kind == .string && typ_sym.has_method('str') {
 					continue
 				}
-				// TODO const bug
 				if typ_sym.kind == .void && arg_typ_sym.kind == .string {
 					continue
 				}
@@ -570,17 +573,56 @@ fn (c mut Checker) stmt(node ast.Stmt) {
 			c.stmts(it.stmts)
 		}
 		ast.ConstDecl {
+			mut unresolved_num:= 0 // number of type-unresolved consts
+			mut ordered_exprs := []ast.Expr
+			mut ordered_fields := []ast.Field
 			for i, expr in it.exprs {
 				mut field := it.fields[i]
 				typ := c.expr(expr)
-				// TODO: once consts are fixed update here
+				if typ == table.void_type {
+					unresolved_num++
+				}
+				else { // succeed in resolving type
 					c.table.register_const(table.Var{
 						name: field.name
 						typ: typ
 					})
 					field.typ = typ
 					it.fields[i] = field
+					ordered_exprs << expr
+					ordered_fields << field
+					if unresolved_num == 0 {
+						continue
 					}
+					for j, _expr in it.exprs[0..i]{
+						mut _field := it.fields[j]
+						_typ := c.expr(_expr)
+						if _field.typ == 0 && _typ != table.void_type {
+							// succeed in resolving type
+							c.table.register_const(table.Var{
+								name: _field.name
+								typ: _typ
+							})
+							unresolved_num--
+							_field.typ = _typ
+							it.fields[j] = _field
+							ordered_exprs << _expr
+							ordered_fields << _field
+						}
+					}
+				}
+			}
+			if unresolved_num != 0 {
+				c.error("$unresolved_num ill-defined consts are in use", it.pos)
+			}
+			for i, field in ordered_fields { // set the fields and exprs as ordered
+				it.fields[i] = field
+				it.exprs[i] = ordered_exprs[i]
+			}
+			/*
+			it.exprs = ordered_exprs
+			it.fields = ordered_fields
+			*/
 		}
 		ast.ExprStmt {
 			c.expr(it.expr)

vlib/v/parser/parser.v

@@ -1440,6 +1440,7 @@ fn (p mut Parser) const_decl() ast.ConstDecl {
 	if is_pub {
 		p.next()
 	}
+	pos := p.tok.position()
 	p.check(.key_const)
 	p.check(.lpar)
 	mut fields := []ast.Field
@@ -1463,6 +1464,7 @@ fn (p mut Parser) const_decl() ast.ConstDecl {
 	}
 	p.check(.rpar)
 	return ast.ConstDecl{
+		pos : pos
 		fields: fields
 		exprs: exprs
 		is_pub: is_pub

vlib/v/tests/const_test.v

@@ -1,6 +1,6 @@
 pub const (
-	// c = a // TODO
 	a = b
+	c = a + b
 	b = 1
 	d = (e / 2) + 7
 	e = 9