-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 clippy_utils::diagnostics::span_lint_and_then;
+use clippy_utils::paths;
+use clippy_utils::source::{snippet, snippet_opt};
+use clippy_utils::sugg::Sugg;
+use clippy_utils::ty::is_type_diagnostic_item;
+use clippy_utils::{is_expn_of, last_path_segment, match_def_path, match_function_call};
use if_chain::if_chain;
-use rustc::hir::*;
-use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
-use rustc::ty;
-use rustc::{declare_tool_lint, lint_array};
+use rustc_ast::ast::LitKind;
use rustc_errors::Applicability;
-use syntax::ast::LitKind;
+use rustc_hir::{Arm, BorrowKind, Expr, ExprKind, MatchSource, PatKind};
+use rustc_lint::{LateContext, LateLintPass, LintContext};
+use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_span::source_map::Span;
+use rustc_span::sym;
-/// **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
-/// 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:**
-/// ```rust
-/// format!("foo")
-/// format!("{}", foo)
-/// ```
declare_clippy_lint! {
+ /// **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
+ /// 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:**
+ /// ```rust
+ ///
+ /// // Bad
+ /// let foo = "foo";
+ /// format!("{}", foo);
+ ///
+ /// // Good
+ /// foo.to_owned();
+ /// ```
pub USELESS_FORMAT,
complexity,
"useless use of `format!`"
}
-#[derive(Copy, Clone, Debug)]
-pub struct Pass;
+declare_lint_pass!(UselessFormat => [USELESS_FORMAT]);
+
+impl<'tcx> LateLintPass<'tcx> for UselessFormat {
+ fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
+ let span = match is_expn_of(expr.span, "format") {
+ Some(s) if !s.from_expansion() => s,
+ _ => return,
+ };
-impl LintPass for Pass {
- fn get_lints(&self) -> LintArray {
- lint_array![USELESS_FORMAT]
+ // 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 name(&self) -> &'static str {
- "UselessFormat"
+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!`", |diag| {
+ diag.span_suggestion(
+ to_replace,
+ help,
+ sugg,
+ Applicability::MachineApplicable, // snippet
+ );
+ });
}
-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;
+fn on_argumentv1_new<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, arms: &'tcx [Arm<'_>]) -> Option<String> {
+ if_chain! {
+ if let ExprKind::AddrOf(BorrowKind::Ref, _, format_args) = expr.kind;
+ if let ExprKind::Array(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.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(pats, None) = arms[0].pat.kind;
+ if pats.len() == 1;
+ then {
+ let ty = cx.typeck_results().pat_ty(pats[0]).peel_refs();
+ if *ty.kind() != rustc_middle::ty::Str && !is_type_diagnostic_item(cx, ty, sym::string_type) {
+ return None;
}
- match expr.node {
- // `format!("{}", foo)` expansion
- ExprKind::Call(ref fun, ref args) => {
- if_chain! {
- if let ExprKind::Path(ref qpath) = fun.node;
- if let Some(fun_def_id) = opt_def_id(resolve_node(cx, qpath, fun.hir_id));
- 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 {
- 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_lint_and_then(cx, USELESS_FORMAT, span, "useless use of `format!`", |db| {
- db.span_suggestion(
- expr.span,
- message,
- sugg,
- Applicability::MachineApplicable,
- );
- });
- }
- }
- },
- // `format!("foo")` expansion contains `match () { () => [], }`
- 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_lint_and_then(cx, USELESS_FORMAT, span, "useless use of `format!`", |db| {
- db.span_suggestion(
- span,
- "consider using .to_string()",
- sugg,
- Applicability::MachineApplicable, // snippet
- );
- });
- }
+ 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 sugg = Sugg::hir(cx, format_args, "<arg>");
+ if let ExprKind::MethodCall(path, _, _, _) = format_args.kind {
+ if path.ident.name == sym!(to_string) {
+ return Some(format!("{}", sugg));
}
- },
- _ => (),
+ } else if let ExprKind::Binary(..) = format_args.kind {
+ return Some(format!("{}", sugg));
+ }
+ return Some(format!("{}.to_string()", sugg.maybe_par()));
}
}
}
+ None
}
-/// Checks if the expressions matches `&[""]`
-fn check_single_piece(expr: &Expr) -> bool {
+fn on_new_v1<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> Option<String> {
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::Lit(ref lit) = exprs[0].node;
- if let LitKind::Str(ref lit, _) = lit.node;
+ 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, _, arr) = args[0].kind;
+ if let ExprKind::Array(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, _, arg1) = args[1].kind;
+ if let ExprKind::Match(matchee, arms, MatchSource::Normal) = arg1.kind;
+ if arms.len() == 1;
+ if let ExprKind::Tup(tup) = matchee.kind;
then {
- return lit.as_str().is_empty();
+ // `format!("foo")` expansion contains `match () { () => [], }`
+ if tup.is_empty() {
+ if let Some(s_src) = snippet_opt(cx, lit.span) {
+ // Simulate macro expansion, converting {{ and }} to { and }.
+ let s_expand = s_src.replace("{{", "{").replace("}}", "}");
+ return Some(format!("{}.to_string()", s_expand));
+ }
+ } else if s.as_str().is_empty() {
+ return on_argumentv1_new(cx, &tup[0], arms);
+ }
}
}
-
- false
+ None
}
-/// Checks if the expressions matches
-/// ```rust,ignore
-/// &match (&"arg",) {
-/// (__arg0,) => [::std::fmt::ArgumentV1::new(__arg0,
-/// ::std::fmt::Display::fmt)],
-/// }
-/// ```
-/// 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> {
+fn on_new_v1_fmt<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> Option<String> {
if_chain! {
- if let ExprKind::AddrOf(_, ref expr) = expr.node;
- if let ExprKind::Match(ref match_expr, ref arms, _) = expr.node;
+ 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, _, arr) = args[0].kind;
+ if let ExprKind::Array(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, _, arg1) = args[1].kind;
+ if let ExprKind::Match(matchee, arms, MatchSource::Normal) = arg1.kind;
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 ExprKind::Array(ref exprs) = arms[0].body.node;
- if exprs.len() == 1;
- if let ExprKind::Call(_, ref args) = exprs[0].node;
- if args.len() == 2;
- 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);
+ if let ExprKind::Tup(tup) = matchee.kind;
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]);
- }
- }
+ return on_argumentv1_new(cx, &tup[0], arms);
}
}
-
None
}
/// &[_ {
/// format: _ {
/// width: _::Implied,
+/// precision: _::Implied,
/// ...
/// },
/// ...,
/// }]
/// ```
-fn check_unformatted(expr: &Expr) -> bool {
+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 let ExprKind::AddrOf(BorrowKind::Ref, _, expr) = expr.kind;
+ if let ExprKind::Array(exprs) = expr.kind;
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";
+ // struct `core::fmt::rt::v1::Argument`
+ if let ExprKind::Struct(_, 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(_, 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;
}