-use crate::utils::paths;
-use crate::utils::{
- is_expn_of, last_path_segment, match_def_path, match_function_call, match_type, snippet, span_lint_and_then,
- walk_ptrs_ty,
-};
+use clippy_utils::diagnostics::span_lint_and_sugg;
+use clippy_utils::macros::{root_macro_call_first_node, FormatArgsExpn};
+use clippy_utils::source::{snippet_opt, snippet_with_applicability};
+use clippy_utils::sugg::Sugg;
use if_chain::if_chain;
-use rustc_ast::ast::LitKind;
use rustc_errors::Applicability;
-use rustc_hir::{Arm, BorrowKind, Expr, ExprKind, MatchSource, PatKind};
-use rustc_lint::{LateContext, LateLintPass, LintContext};
+use rustc_hir::{Expr, ExprKind};
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_middle::ty;
use rustc_session::{declare_lint_pass, declare_tool_lint};
-use rustc_span::source_map::Span;
+use rustc_span::symbol::kw;
+use rustc_span::{sym, Span};
declare_clippy_lint! {
- /// **What it does:** Checks for the use of `format!("string literal with no
+ /// ### 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!("foo")` 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()`
/// if `foo: &str`.
///
- /// **Known problems:** None.
- ///
- /// **Examples:**
+ /// ### Examples
/// ```rust
- /// # let foo = "foo";
- /// format!("foo");
+ /// let foo = "foo";
/// format!("{}", foo);
/// ```
+ ///
+ /// Use instead:
+ /// ```rust
+ /// let foo = "foo";
+ /// foo.to_owned();
+ /// ```
+ #[clippy::version = "pre 1.29.0"]
pub USELESS_FORMAT,
complexity,
"useless use of `format!`"
declare_lint_pass!(UselessFormat => [USELESS_FORMAT]);
-impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UselessFormat {
- fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) {
- let span = match is_expn_of(expr.span, "format") {
- Some(s) if !s.from_expansion() => s,
- _ => return,
+impl<'tcx> LateLintPass<'tcx> for UselessFormat {
+ fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
+ let (format_args, call_site) = if_chain! {
+ if let Some(macro_call) = root_macro_call_first_node(cx, expr);
+ if cx.tcx.is_diagnostic_item(sym::format_macro, macro_call.def_id);
+ if let Some(format_args) = FormatArgsExpn::find_nested(cx, expr, macro_call.expn);
+ then {
+ (format_args, macro_call.span)
+ } else {
+ return
+ }
};
- // Operate on the only argument of `alloc::fmt::format`.
- if let Some(sugg) = on_new_v1(cx, expr) {
- span_useless_format(cx, span, "consider using `.to_string()`", sugg);
- } else if let Some(sugg) = on_new_v1_fmt(cx, expr) {
- span_useless_format(cx, span, "consider using `.to_string()`", sugg);
- }
- }
-}
-
-fn span_useless_format<T: LintContext>(cx: &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
- );
- });
-}
-
-fn on_argumentv1_new<'a, 'tcx>(
- cx: &LateContext<'a, 'tcx>,
- expr: &'tcx Expr<'_>,
- arms: &'tcx [Arm<'_>],
-) -> Option<String> {
- if_chain! {
- if let ExprKind::AddrOf(BorrowKind::Ref, _, ref format_args) = expr.kind;
- if let ExprKind::Array(ref elems) = arms[0].body.kind;
- if elems.len() == 1;
- if let Some(args) = match_function_call(cx, &elems[0], &paths::FMT_ARGUMENTV1_NEW);
- // matches `core::fmt::Display::fmt`
- if args.len() == 2;
- if let ExprKind::Path(ref qpath) = args[1].kind;
- if let Some(did) = cx.tables.qpath_res(qpath, args[1].hir_id).opt_def_id();
- if match_def_path(cx, did, &paths::DISPLAY_FMT_METHOD);
- // check `(arg0,)` in match block
- if let PatKind::Tuple(ref pats, None) = arms[0].pat.kind;
- if pats.len() == 1;
- then {
- let ty = walk_ptrs_ty(cx.tables.pat_ty(&pats[0]));
- if ty.kind != rustc::ty::Str && !match_type(cx, ty, &paths::STRING) {
- return None;
- }
- if let ExprKind::Lit(ref lit) = format_args.kind {
- if let LitKind::Str(ref s, _) = lit.node {
- return Some(format!("{:?}.to_string()", s.as_str()));
- }
- } else {
- let snip = snippet(cx, format_args.span, "<arg>");
- if let ExprKind::MethodCall(ref path, _, _) = format_args.kind {
- if path.ident.name == sym!(to_string) {
- return Some(format!("{}", snip));
+ let mut applicability = Applicability::MachineApplicable;
+ if format_args.value_args.is_empty() {
+ match *format_args.format_string_parts {
+ [] => span_useless_format_empty(cx, call_site, "String::new()".to_owned(), applicability),
+ [_] => {
+ if let Some(s_src) = snippet_opt(cx, format_args.format_string_span) {
+ // Simulate macro expansion, converting {{ and }} to { and }.
+ let s_expand = s_src.replace("{{", "{").replace("}}", "}");
+ let sugg = format!("{}.to_string()", s_expand);
+ span_useless_format(cx, call_site, sugg, applicability);
}
- } else if let ExprKind::Binary(..) = format_args.kind {
- return Some(format!("{}", snip));
- }
- return Some(format!("{}.to_string()", snip));
+ },
+ [..] => {},
}
- }
- }
- None
-}
-
-fn on_new_v1<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) -> Option<String> {
- if_chain! {
- if let Some(args) = match_function_call(cx, expr, &paths::FMT_ARGUMENTS_NEW_V1);
- if args.len() == 2;
- // Argument 1 in `new_v1()`
- if let ExprKind::AddrOf(BorrowKind::Ref, _, ref arr) = args[0].kind;
- if let ExprKind::Array(ref pieces) = arr.kind;
- if pieces.len() == 1;
- if let ExprKind::Lit(ref lit) = pieces[0].kind;
- if let LitKind::Str(ref s, _) = lit.node;
- // Argument 2 in `new_v1()`
- if let ExprKind::AddrOf(BorrowKind::Ref, _, ref arg1) = args[1].kind;
- if let ExprKind::Match(ref matchee, ref arms, MatchSource::Normal) = arg1.kind;
- if arms.len() == 1;
- if let ExprKind::Tup(ref tup) = matchee.kind;
- then {
- // `format!("foo")` expansion contains `match () { () => [], }`
- if tup.is_empty() {
- return Some(format!("{:?}.to_string()", s.as_str()));
- } else if s.as_str().is_empty() {
- return on_argumentv1_new(cx, &tup[0], arms);
+ } else if let [value] = *format_args.value_args {
+ if_chain! {
+ if format_args.format_string_parts == [kw::Empty];
+ if match cx.typeck_results().expr_ty(value).peel_refs().kind() {
+ ty::Adt(adt, _) => cx.tcx.is_diagnostic_item(sym::String, adt.did()),
+ ty::Str => true,
+ _ => false,
+ };
+ if let Some(args) = format_args.args();
+ if args.iter().all(|arg| arg.format_trait == sym::Display && !arg.has_string_formatting());
+ then {
+ let is_new_string = match value.kind {
+ ExprKind::Binary(..) => true,
+ ExprKind::MethodCall(path, ..) => path.ident.name == sym::to_string,
+ _ => false,
+ };
+ let sugg = if is_new_string {
+ snippet_with_applicability(cx, value.span, "..", &mut applicability).into_owned()
+ } else {
+ let sugg = Sugg::hir_with_applicability(cx, value, "<arg>", &mut applicability);
+ format!("{}.to_string()", sugg.maybe_par())
+ };
+ span_useless_format(cx, call_site, sugg, applicability);
+ }
}
- }
+ };
}
- None
}
-fn on_new_v1_fmt<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) -> Option<String> {
- if_chain! {
- if let Some(args) = match_function_call(cx, expr, &paths::FMT_ARGUMENTS_NEW_V1_FORMATTED);
- if args.len() == 3;
- if check_unformatted(&args[2]);
- // Argument 1 in `new_v1_formatted()`
- if let ExprKind::AddrOf(BorrowKind::Ref, _, ref arr) = args[0].kind;
- if let ExprKind::Array(ref pieces) = arr.kind;
- if pieces.len() == 1;
- if let ExprKind::Lit(ref lit) = pieces[0].kind;
- if let LitKind::Str(..) = lit.node;
- // Argument 2 in `new_v1_formatted()`
- if let ExprKind::AddrOf(BorrowKind::Ref, _, ref arg1) = args[1].kind;
- if let ExprKind::Match(ref matchee, ref arms, MatchSource::Normal) = arg1.kind;
- if arms.len() == 1;
- if let ExprKind::Tup(ref tup) = matchee.kind;
- then {
- return on_argumentv1_new(cx, &tup[0], arms);
- }
- }
- None
+fn span_useless_format_empty(cx: &LateContext<'_>, span: Span, sugg: String, applicability: Applicability) {
+ span_lint_and_sugg(
+ cx,
+ USELESS_FORMAT,
+ span,
+ "useless use of `format!`",
+ "consider using `String::new()`",
+ sugg,
+ applicability,
+ );
}
-/// Checks if the expression matches
-/// ```rust,ignore
-/// &[_ {
-/// format: _ {
-/// width: _::Implied,
-/// precision: _::Implied,
-/// ...
-/// },
-/// ...,
-/// }]
-/// ```
-fn check_unformatted(expr: &Expr<'_>) -> bool {
- if_chain! {
- if let ExprKind::AddrOf(BorrowKind::Ref, _, ref expr) = expr.kind;
- if let ExprKind::Array(ref exprs) = expr.kind;
- if exprs.len() == 1;
- // struct `core::fmt::rt::v1::Argument`
- if let ExprKind::Struct(_, ref fields, _) = exprs[0].kind;
- if let Some(format_field) = fields.iter().find(|f| f.ident.name == sym!(format));
- // struct `core::fmt::rt::v1::FormatSpec`
- if let ExprKind::Struct(_, ref fields, _) = format_field.expr.kind;
- if let Some(precision_field) = fields.iter().find(|f| f.ident.name == sym!(precision));
- if let ExprKind::Path(ref precision_path) = precision_field.expr.kind;
- if last_path_segment(precision_path).ident.name == sym!(Implied);
- if let Some(width_field) = fields.iter().find(|f| f.ident.name == sym!(width));
- if let ExprKind::Path(ref width_qpath) = width_field.expr.kind;
- if last_path_segment(width_qpath).ident.name == sym!(Implied);
- then {
- return true;
- }
- }
-
- false
+fn span_useless_format(cx: &LateContext<'_>, span: Span, sugg: String, applicability: Applicability) {
+ span_lint_and_sugg(
+ cx,
+ USELESS_FORMAT,
+ span,
+ "useless use of `format!`",
+ "consider using `.to_string()`",
+ sugg,
+ applicability,
+ );
}
projects / rust.git / blobdiff