189 lines
7.3 KiB
Rust
189 lines
7.3 KiB
Rust
use crate::rustc::hir::*;
|
|
use crate::rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
|
|
use crate::rustc::{declare_tool_lint, lint_array};
|
|
use if_chain::if_chain;
|
|
use crate::rustc::ty;
|
|
use crate::syntax::ast::LitKind;
|
|
use crate::syntax_pos::Span;
|
|
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 crate::rustc_errors::Applicability;
|
|
|
|
/// **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
|
|
/// 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! {
|
|
pub USELESS_FORMAT,
|
|
complexity,
|
|
"useless use of `format!`"
|
|
}
|
|
|
|
#[derive(Copy, Clone, Debug)]
|
|
pub struct Pass;
|
|
|
|
impl LintPass for Pass {
|
|
fn get_lints(&self) -> LintArray {
|
|
lint_array![USELESS_FORMAT]
|
|
}
|
|
}
|
|
|
|
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
|
|
ExprKind::Call(ref fun, ref args) => {
|
|
if_chain! {
|
|
if let ExprKind::Path(ref qpath) = fun.node;
|
|
if args.len() == 3;
|
|
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_NEWV1FORMATTED);
|
|
if check_single_piece(&args[0]);
|
|
if let Some(format_arg) = get_single_string_arg(cx, &args[1]);
|
|
if 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, ref span, ref expr) = 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_with_applicability(
|
|
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_with_applicability(
|
|
span,
|
|
"consider using .to_string()",
|
|
sugg,
|
|
Applicability::MachineApplicable, // snippet
|
|
);
|
|
});
|
|
}
|
|
},
|
|
_ => (),
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Checks if the expressions matches `&[""]`
|
|
fn check_single_piece(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::Lit(ref lit) = exprs[0].node;
|
|
if let LitKind::Str(ref lit, _) = lit.node;
|
|
then {
|
|
return lit.as_str().is_empty();
|
|
}
|
|
}
|
|
|
|
false
|
|
}
|
|
|
|
/// 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> {
|
|
if_chain! {
|
|
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 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);
|
|
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
|
|
}
|
|
|
|
/// 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;
|
|
}
|
|
}
|
|
|
|
false
|
|
}
|