+use crate::utils::paths;
+use crate::utils::{
+ in_macro, is_expn_of, last_path_segment, match_def_path, match_type, opt_def_id, resolve_node, snippet,
+ span_lint_and_then, walk_ptrs_ty,
+};
+use if_chain::if_chain;
use rustc::hir::*;
-use rustc::lint::*;
+use rustc::lint::{LateContext, LateLintPass, LintArray, LintContext, LintPass};
use rustc::ty;
+use rustc::{declare_tool_lint, lint_array};
+use rustc_errors::Applicability;
use syntax::ast::LitKind;
-use utils::paths;
-use utils::{is_expn_of, match_def_path, match_type, opt_def_id, resolve_node, span_lint, walk_ptrs_ty};
+use syntax::source_map::Span;
/// **What it does:** Checks for the use of `format!("string literal with no
/// argument")` and `format!("{}", foo)` where `foo` is a string.
///
-/// **Why is this bad?** There is no point of doing that. `format!("too")` can
+/// **Why is this bad?** There is no point of doing that. `format!("foo")` can
/// be replaced by `"foo".to_owned()` if you really need a `String`. The even
/// worse `&format!("foo")` is often encountered in the wild. `format!("{}",
/// foo)` can be replaced by `foo.clone()` if `foo: String` or `foo.to_owned()`
/// format!("foo")
/// format!("{}", foo)
/// ```
-declare_lint! {
+declare_clippy_lint! {
pub USELESS_FORMAT,
- Warn,
+ complexity,
"useless use of `format!`"
}
fn get_lints(&self) -> LintArray {
lint_array![USELESS_FORMAT]
}
+
+ fn name(&self) -> &'static str {
+ "UselessFormat"
+ }
}
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
if let Some(span) = is_expn_of(expr.span, "format") {
+ if in_macro(span) {
+ return;
+ }
match expr.node {
// `format!("{}", foo)` expansion
- ExprCall(ref fun, ref args) => {
+ ExprKind::Call(ref fun, ref args) => {
if_chain! {
- if let ExprPath(ref qpath) = fun.node;
- if args.len() == 2;
+ if let ExprKind::Path(ref qpath) = fun.node;
if let Some(fun_def_id) = opt_def_id(resolve_node(cx, qpath, fun.hir_id));
- if match_def_path(cx.tcx, fun_def_id, &paths::FMT_ARGUMENTS_NEWV1);
- // ensure the format string is `"{..}"` with only one argument and no text
- if check_static_str(&args[0]);
- // ensure the format argument is `{}` ie. Display with no fancy option
- // and that the argument is a string
- if check_arg_is_display(cx, &args[1]);
+ let new_v1 = match_def_path(cx.tcx, fun_def_id, &paths::FMT_ARGUMENTS_NEWV1);
+ let new_v1_fmt = match_def_path(
+ cx.tcx,
+ fun_def_id,
+ &paths::FMT_ARGUMENTS_NEWV1FORMATTED
+ );
+ if new_v1 || new_v1_fmt;
+ if check_single_piece(&args[0]);
+ if let Some(format_arg) = get_single_string_arg(cx, &args[1]);
+ if new_v1 || check_unformatted(&args[2]);
+ if let ExprKind::AddrOf(_, ref format_arg) = format_arg.node;
then {
- span_lint(cx, USELESS_FORMAT, span, "useless use of `format!`");
+ let (message, sugg) = if_chain! {
+ if let ExprKind::MethodCall(ref path, _, _) = format_arg.node;
+ if path.ident.as_interned_str() == "to_string";
+ then {
+ ("`to_string()` is enough",
+ snippet(cx, format_arg.span, "<arg>").to_string())
+ } else {
+ ("consider using .to_string()",
+ format!("{}.to_string()", snippet(cx, format_arg.span, "<arg>")))
+ }
+ };
+
+ span_useless_format(cx, span, message, sugg);
}
}
},
// `format!("foo")` expansion contains `match () { () => [], }`
- ExprMatch(ref matchee, _, _) => if let ExprTup(ref tup) = matchee.node {
- if tup.is_empty() {
- span_lint(cx, USELESS_FORMAT, span, "useless use of `format!`");
+ ExprKind::Match(ref matchee, _, _) => {
+ if let ExprKind::Tup(ref tup) = matchee.node {
+ if tup.is_empty() {
+ let sugg = format!("{}.to_string()", snippet(cx, expr.span, "<expr>").into_owned());
+ span_useless_format(cx, span, "consider using .to_string()", sugg);
+ }
}
},
_ => (),
}
}
+fn span_useless_format<'a, 'tcx: 'a, T: LintContext<'tcx>>(cx: &'a T, span: Span, help: &str, mut sugg: String) {
+ let to_replace = span.source_callsite();
+
+ // The callsite span contains the statement semicolon for some reason.
+ let snippet = snippet(cx, to_replace, "..");
+ if snippet.ends_with(';') {
+ sugg.push(';');
+ }
+
+ span_lint_and_then(cx, USELESS_FORMAT, span, "useless use of `format!`", |db| {
+ db.span_suggestion(
+ to_replace,
+ help,
+ sugg,
+ Applicability::MachineApplicable, // snippet
+ );
+ });
+}
+
/// Checks if the expressions matches `&[""]`
-fn check_static_str(expr: &Expr) -> bool {
+fn check_single_piece(expr: &Expr) -> bool {
if_chain! {
- if let ExprAddrOf(_, ref expr) = expr.node; // &[""]
- if let ExprArray(ref exprs) = expr.node; // [""]
+ if let ExprKind::AddrOf(_, ref expr) = expr.node; // &[""]
+ if let ExprKind::Array(ref exprs) = expr.node; // [""]
if exprs.len() == 1;
- if let ExprLit(ref lit) = exprs[0].node;
+ if let ExprKind::Lit(ref lit) = exprs[0].node;
if let LitKind::Str(ref lit, _) = lit.node;
then {
return lit.as_str().is_empty();
/// Checks if the expressions matches
/// ```rust,ignore
-/// &match (&42,) {
+/// &match (&"arg",) {
/// (__arg0,) => [::std::fmt::ArgumentV1::new(__arg0,
/// ::std::fmt::Display::fmt)],
/// }
/// ```
-fn check_arg_is_display(cx: &LateContext, expr: &Expr) -> bool {
+/// and that the type of `__arg0` is `&str` or `String`,
+/// then returns the span of first element of the matched tuple.
+fn get_single_string_arg<'a>(cx: &LateContext<'_, '_>, expr: &'a Expr) -> Option<&'a Expr> {
if_chain! {
- if let ExprAddrOf(_, ref expr) = expr.node;
- if let ExprMatch(_, ref arms, _) = expr.node;
+ if let ExprKind::AddrOf(_, ref expr) = expr.node;
+ if let ExprKind::Match(ref match_expr, ref arms, _) = expr.node;
if arms.len() == 1;
if arms[0].pats.len() == 1;
if let PatKind::Tuple(ref pat, None) = arms[0].pats[0].node;
if pat.len() == 1;
- if let ExprArray(ref exprs) = arms[0].body.node;
+ if let ExprKind::Array(ref exprs) = arms[0].body.node;
if exprs.len() == 1;
- if let ExprCall(_, ref args) = exprs[0].node;
+ if let ExprKind::Call(_, ref args) = exprs[0].node;
if args.len() == 2;
- if let ExprPath(ref qpath) = args[1].node;
+ if let ExprKind::Path(ref qpath) = args[1].node;
if let Some(fun_def_id) = opt_def_id(resolve_node(cx, qpath, args[1].hir_id));
if match_def_path(cx.tcx, fun_def_id, &paths::DISPLAY_FMT_METHOD);
then {
let ty = walk_ptrs_ty(cx.tables.pat_ty(&pat[0]));
+ if ty.sty == ty::Str || match_type(cx, ty, &paths::STRING) {
+ if let ExprKind::Tup(ref values) = match_expr.node {
+ return Some(&values[0]);
+ }
+ }
+ }
+ }
+
+ None
+}
- return ty.sty == ty::TyStr || match_type(cx, ty, &paths::STRING);
+/// Checks if the expression matches
+/// ```rust,ignore
+/// &[_ {
+/// format: _ {
+/// width: _::Implied,
+/// ...
+/// },
+/// ...,
+/// }]
+/// ```
+fn check_unformatted(expr: &Expr) -> bool {
+ if_chain! {
+ if let ExprKind::AddrOf(_, ref expr) = expr.node;
+ if let ExprKind::Array(ref exprs) = expr.node;
+ if exprs.len() == 1;
+ if let ExprKind::Struct(_, ref fields, _) = exprs[0].node;
+ if let Some(format_field) = fields.iter().find(|f| f.ident.name == "format");
+ if let ExprKind::Struct(_, ref fields, _) = format_field.expr.node;
+ if let Some(width_field) = fields.iter().find(|f| f.ident.name == "width");
+ if let ExprKind::Path(ref width_qpath) = width_field.expr.node;
+ if last_path_segment(width_qpath).ident.name == "Implied";
+ if let Some(precision_field) = fields.iter().find(|f| f.ident.name == "precision");
+ if let ExprKind::Path(ref precision_path) = precision_field.expr.node;
+ if last_path_segment(precision_path).ident.name == "Implied";
+ then {
+ return true;
}
}
projects / rust.git / blobdiff