diff --git a/clippy_lints/src/format.rs b/clippy_lints/src/format.rs index 688d8f8630f3..395c920c9974 100644 --- a/clippy_lints/src/format.rs +++ b/clippy_lints/src/format.rs @@ -9,7 +9,7 @@ use rustc_lint::{LateContext, LateLintPass}; use rustc_middle::ty; use rustc_session::{declare_lint_pass, declare_tool_lint}; use rustc_span::symbol::kw; -use rustc_span::{sym, Span}; +use rustc_span::{sym, BytePos, Span}; declare_clippy_lint! { /// ### What it does @@ -84,7 +84,22 @@ impl<'tcx> LateLintPass<'tcx> for UselessFormat { ExprKind::MethodCall(path, ..) => path.ident.name.as_str() == "to_string", _ => false, }; - let sugg = if is_new_string { + let sugg = if format_args.format_string_span.contains(value.span) { + // Implicit argument. e.g. `format!("{x}")` span points to `{x}` + let spdata = value.span.data(); + let span = Span::new( + spdata.lo + BytePos(1), + spdata.hi - BytePos(1), + spdata.ctxt, + spdata.parent + ); + let snip = snippet_with_applicability(cx, span, "..", &mut applicability); + if is_new_string { + snip.into() + } else { + format!("{snip}.to_string()") + } + } else if is_new_string { snippet_with_applicability(cx, value.span, "..", &mut applicability).into_owned() } else { let sugg = Sugg::hir_with_applicability(cx, value, "", &mut applicability); diff --git a/tests/ui/format.fixed b/tests/ui/format.fixed index 64cb7b1cfb80..78d2bfd474e4 100644 --- a/tests/ui/format.fixed +++ b/tests/ui/format.fixed @@ -73,4 +73,10 @@ fn main() { let _s: String = (&*v.join("\n")).to_string(); format!("prepend {:+}", "s"); + + // Issue #8290 + let x = "foo"; + let _ = x.to_string(); + let _ = format!("{x:?}"); // Don't lint on debug + let _ = x.to_string(); } diff --git a/tests/ui/format.rs b/tests/ui/format.rs index a065b1b5683c..009c1aa216fc 100644 --- a/tests/ui/format.rs +++ b/tests/ui/format.rs @@ -75,4 +75,10 @@ fn main() { let _s: String = format!("{}", &*v.join("\n")); format!("prepend {:+}", "s"); + + // Issue #8290 + let x = "foo"; + let _ = format!("{x}"); + let _ = format!("{x:?}"); // Don't lint on debug + let _ = format!("{y}", y = x); } diff --git a/tests/ui/format.stderr b/tests/ui/format.stderr index 58ad7499bb26..660be57585e3 100644 --- a/tests/ui/format.stderr +++ b/tests/ui/format.stderr @@ -99,5 +99,17 @@ error: useless use of `format!` LL | let _s: String = format!("{}", &*v.join("/n")); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `.to_string()`: `(&*v.join("/n")).to_string()` -error: aborting due to 15 previous errors +error: useless use of `format!` + --> $DIR/format.rs:81:13 + | +LL | let _ = format!("{x}"); + | ^^^^^^^^^^^^^^ help: consider using `.to_string()`: `x.to_string()` + +error: useless use of `format!` + --> $DIR/format.rs:83:13 + | +LL | let _ = format!("{y}", y = x); + | ^^^^^^^^^^^^^^^^^^^^^ help: consider using `.to_string()`: `x.to_string()` + +error: aborting due to 17 previous errors