v: deprecate `[if ident]` in favour of `[if ident ?]`

vlib/builtin/option.v

@@ -35,7 +35,7 @@ fn (_ None__) str() string {
 	return 'none'
 }
 
-[if trace_error]
+[if trace_error ?]
 fn trace_error(x string) {
 	eprintln('> ${@FN} | $x')
 }

vlib/v/ast/str.v

@@ -340,10 +340,9 @@ pub fn (x Expr) str() string {
 			return '($x.expr)'
 		}
 		PostfixExpr {
-			// TODO: uncomment after [if x] is deprecated
-			// if x.op == .question {
-			//	return '$x.expr ?'
-			//}
+			if x.op == .question {
+				return '$x.expr ?'
+			}
 			return '$x.expr$x.op'
 		}
 		PrefixExpr {

vlib/v/checker/checker.v

@@ -7259,8 +7259,8 @@ fn (mut c Checker) evaluate_once_comptime_if_attribute(mut a ast.Attr) bool {
 			return a.ct_skip
 		} else {
 			if a.ct_expr.name !in checker.valid_comp_not_user_defined {
-				// TODO: uncomment after [if x] is deprecated in favour of [if x?], see also vlib/v/ast/str.v:343
-				// c.note('`[if $a.ct_expr.name]` is deprecated. Use `[if $a.ct_expr.name ?]` instead', a.pos)
+				c.note('`[if $a.ct_expr.name]` is deprecated. Use `[if $a.ct_expr.name ?]` instead',
+					a.pos)
 				a.ct_skip = a.ct_expr.name !in c.pref.compile_defines
 				a.ct_evaled = true
 				return a.ct_skip

vlib/v/gen/c/cgen.v

@@ -2836,7 +2836,7 @@ fn (mut g Gen) autofree_scope_vars_stop(pos int, line_nr int, free_parent_scopes
 		stop_pos)
 }
 
-[if trace_autofree]
+[if trace_autofree ?]
 fn (mut g Gen) trace_autofree(line string) {
 	g.writeln(line)
 }

vlib/v/parser/parser.v

@@ -1553,9 +1553,7 @@ fn (mut p Parser) parse_attr() ast.Attr {
 		p.inside_if_expr = false
 		p.inside_ct_if_expr = false
 		if comptime_cond is ast.PostfixExpr {
-			x := comptime_cond as ast.PostfixExpr
 			comptime_cond_opt = true
-			comptime_cond = x.expr
 		}
 		name = comptime_cond.str()
 	} else if p.tok.kind == .string {

vlib/v/util/module.v

@@ -3,7 +3,7 @@ module util
 import os
 import v.pref
 
-[if trace_mod_path_to_full_name]
+[if trace_mod_path_to_full_name ?]
 fn trace_mod_path_to_full_name(line string, mod string, file_path string, res string) {
 	eprintln('> $line ${@FN} mod: ${mod:-20} | file_path: ${file_path:-30} | result: $res')
 }