vet: give notice for replacing const dynamic arrays with const fixed ones (#18960)

cmd/tools/vvet/tests/const_dynamic_array_notice.out

@@ -0,0 +1 @@
+cmd/tools/vvet/tests/const_dynamic_array_notice.vv:1: notice: use a fixed array, instead of a dynamic one

cmd/tools/vvet/tests/const_dynamic_array_notice.vv

@@ -0,0 +1 @@
+const a = [1, 2, 3]

cmd/tools/vvet/vvet.v

@@ -14,9 +14,10 @@ import term
 struct Vet {
 	opt Options
 mut:
-	errors []vet.Error
-	warns  []vet.Error
-	file   string
+	errors  []vet.Error
+	warns   []vet.Error
+	notices []vet.Error
+	file    string
 }
 
 struct Options {
@@ -69,6 +70,9 @@ fn main() {
 		}
 	}
 	vfmt_err_count := vt.errors.filter(it.fix == .vfmt).len
+	for n in vt.notices {
+		eprintln(vt.e2string(n))
+	}
 	if vt.opt.show_warnings {
 		for w in vt.warns {
 			eprintln(vt.e2string(w))
@@ -100,9 +104,10 @@ fn (mut vt Vet) vet_file(path string) {
 	prefs.is_vsh = path.ends_with('.vsh')
 	table := ast.new_table()
 	vt.vprintln("vetting file '${path}'...")
-	_, errors := parser.parse_vet_file(path, table, prefs)
+	_, errors, notices := parser.parse_vet_file(path, table, prefs)
 	// Transfer errors from scanner and parser
 	vt.errors << errors
+	vt.notices << notices
 	// Scan each line in file for things to improve
 	source_lines := os.read_lines(vt.file) or { []string{} }
 	for lnumber, line in source_lines {
@@ -235,6 +240,7 @@ fn (vt &Vet) e2string(err vet.Error) string {
 		kind = match err.kind {
 			.warning { term.magenta(kind) }
 			.error { term.red(kind) }
+			.notice { term.yellow(kind) }
 		}
 		kind = term.bold(kind)
 		location = term.bold(location)
@@ -275,3 +281,17 @@ fn (mut vt Vet) warn(msg string, line int, fix vet.FixKind) {
 		vt.warns << w
 	}
 }
+
+fn (mut vt Vet) notice(msg string, line int, fix vet.FixKind) {
+	pos := token.Pos{
+		line_nr: line + 1
+	}
+	vt.notices << vet.Error{
+		message: msg
+		file_path: vt.file
+		pos: pos
+		kind: .notice
+		fix: fix
+		typ: .default
+	}
+}

vlib/v/parser/parser.v

@@ -106,6 +106,7 @@ pub mut:
 	warnings       []errors.Warning
 	notices        []errors.Notice
 	vet_errors     []vet.Error
+	vet_notices    []vet.Error
 	template_paths []string // record all compiled $tmpl files; needed for `v watch run webserver.v`
 }
 
@@ -254,7 +255,7 @@ pub fn parse_file(path string, table &ast.Table, comments_mode scanner.CommentsM
 	return res
 }
 
-pub fn parse_vet_file(path string, table_ &ast.Table, pref_ &pref.Preferences) (&ast.File, []vet.Error) {
+pub fn parse_vet_file(path string, table_ &ast.Table, pref_ &pref.Preferences) (&ast.File, []vet.Error, []vet.Error) {
 	$if trace_parse_vet_file ? {
 		eprintln('> ${@MOD}.${@FN} path: ${path}')
 	}
@@ -290,7 +291,7 @@ pub fn parse_vet_file(path string, table_ &ast.Table, pref_ &pref.Preferences) (
 	p.vet_errors << p.scanner.vet_errors
 	file := p.parse()
 	unsafe { p.free_scanner() }
-	return file, p.vet_errors
+	return file, p.vet_errors, p.vet_notices
 }
 
 pub fn (mut p Parser) parse() &ast.File {
@@ -2068,6 +2069,20 @@ fn (mut p Parser) vet_error(msg string, line int, fix vet.FixKind, typ vet.Error
 	}
 }
 
+fn (mut p Parser) vet_notice(msg string, line int, fix vet.FixKind, typ vet.ErrorType) {
+	pos := token.Pos{
+		line_nr: line + 1
+	}
+	p.vet_notices << vet.Error{
+		message: msg
+		file_path: p.scanner.file_path
+		pos: pos
+		kind: .notice
+		fix: fix
+		typ: typ
+	}
+}
+
 fn (mut p Parser) parse_multi_expr(is_top_level bool) ast.Stmt {
 	// in here might be 1) multi-expr 2) multi-assign
 	// 1, a, c ... }       // multi-expression
@@ -3712,6 +3727,10 @@ fn (mut p Parser) const_decl() ast.ConstDecl {
 			return ast.ConstDecl{}
 		}
 		expr := p.expr(0)
+		if expr is ast.ArrayInit && !expr.is_fixed && p.pref.is_vet {
+			p.vet_notice('use a fixed array, instead of a dynamic one', pos.line_nr, vet.FixKind.unknown,
+				.default)
+		}
 		field := ast.ConstField{
 			name: full_name
 			mod: p.mod

vlib/v/vet/vet.v

@@ -7,6 +7,7 @@ import v.token
 pub enum ErrorKind {
 	error
 	warning
+	notice
 }
 
 pub enum FixKind {