Parse the format string for the panic_fmt lint for better warnings.
This commit is contained in:
Mara Bos
parent
0f193d1a62
commit
6b44662669
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@ -3831,6 +3831,7 @@ dependencies = [
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"rustc_hir",
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"rustc_index",
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"rustc_middle",
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"rustc_parse_format",
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"rustc_session",
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"rustc_span",
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"rustc_target",
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@ -20,3 +20,4 @@ rustc_feature = { path = "../rustc_feature" }
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rustc_index = { path = "../rustc_index" }
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rustc_session = { path = "../rustc_session" }
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rustc_trait_selection = { path = "../rustc_trait_selection" }
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rustc_parse_format = { path = "../rustc_parse_format" }
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@ -3,6 +3,7 @@ use rustc_ast as ast;
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use rustc_errors::Applicability;
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use rustc_hir as hir;
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use rustc_middle::ty;
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use rustc_parse_format::{ParseMode, Parser, Piece};
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use rustc_span::sym;
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declare_lint! {
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@ -52,13 +53,28 @@ fn check_panic<'tcx>(cx: &LateContext<'tcx>, f: &'tcx hir::Expr<'tcx>, arg: &'tc
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if cx.tcx.is_diagnostic_item(sym::std_panic_macro, id)
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|| cx.tcx.is_diagnostic_item(sym::core_panic_macro, id)
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{
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let s = sym.as_str();
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if !s.contains(&['{', '}'][..]) {
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let fmt = sym.as_str();
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if !fmt.contains(&['{', '}'][..]) {
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return;
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}
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let s = s.replace("{{", "").replace("}}", "");
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let looks_like_placeholder =
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s.find('{').map_or(false, |i| s[i + 1..].contains('}'));
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let fmt_span = arg.span.source_callsite();
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let (snippet, style) =
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match cx.sess().parse_sess.source_map().span_to_snippet(fmt_span) {
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Ok(snippet) => {
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// Count the number of `#`s between the `r` and `"`.
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let style = snippet.strip_prefix('r').and_then(|s| s.find('"'));
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(Some(snippet), style)
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}
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Err(_) => (None, None),
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};
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let mut fmt_parser =
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Parser::new(fmt.as_ref(), style, snippet, false, ParseMode::Format);
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let n_arguments =
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(&mut fmt_parser).filter(|a| matches!(a, Piece::NextArgument(_))).count();
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// Unwrap another level of macro expansion if this panic!()
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// was expanded from assert!() or debug_assert!().
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for &assert in &[sym::assert_macro, sym::debug_assert_macro] {
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@ -70,15 +86,23 @@ fn check_panic<'tcx>(cx: &LateContext<'tcx>, f: &'tcx hir::Expr<'tcx>, arg: &'tc
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expn = parent;
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}
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}
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if looks_like_placeholder {
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cx.struct_span_lint(PANIC_FMT, arg.span.source_callsite(), |lint| {
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let mut l = lint.build("panic message contains an unused formatting placeholder");
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if n_arguments > 0 && fmt_parser.errors.is_empty() {
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let arg_spans: Vec<_> = match &fmt_parser.arg_places[..] {
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[] => vec![fmt_span],
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v => v.iter().map(|span| fmt_span.from_inner(*span)).collect(),
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};
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cx.struct_span_lint(PANIC_FMT, arg_spans, |lint| {
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let mut l = lint.build(match n_arguments {
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1 => "panic message contains an unused formatting placeholder",
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_ => "panic message contains unused formatting placeholders",
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});
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l.note("this message is not used as a format string when given without arguments, but will be in a future Rust version");
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if expn.call_site.contains(arg.span) {
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l.span_suggestion(
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arg.span.shrink_to_hi(),
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"add the missing argument(s)",
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", argument".into(),
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", ...".into(),
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Applicability::HasPlaceholders,
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);
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l.span_suggestion(
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@ -5,6 +5,6 @@ fn main() {
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panic!("here's a brace: {"); //~ WARN panic message contains a brace
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std::panic!("another one: }"); //~ WARN panic message contains a brace
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core::panic!("Hello {}"); //~ WARN panic message contains an unused formatting placeholder
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assert!(false, "{:03x} bla"); //~ WARN panic message contains an unused formatting placeholder
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assert!(false, "{:03x} {test} bla"); //~ WARN panic message contains unused formatting placeholders
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debug_assert!(false, "{{}} bla"); //~ WARN panic message contains a brace
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}
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@ -24,35 +24,35 @@ LL | std::panic!("{}", "another one: }");
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| ^^^^^
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warning: panic message contains an unused formatting placeholder
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--> $DIR/panic-brace.rs:7:18
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--> $DIR/panic-brace.rs:7:25
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LL | core::panic!("Hello {}");
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| ^^^^^^^^^^
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| ^^
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= note: this message is not used as a format string when given without arguments, but will be in a future Rust version
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help: add the missing argument(s)
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LL | core::panic!("Hello {}", argument);
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| ^^^^^^^^^^
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LL | core::panic!("Hello {}", ...);
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| ^^^^^
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help: or add a "{}" format string to use the message literally
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LL | core::panic!("{}", "Hello {}");
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| ^^^^^
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warning: panic message contains an unused formatting placeholder
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--> $DIR/panic-brace.rs:8:20
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warning: panic message contains unused formatting placeholders
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--> $DIR/panic-brace.rs:8:21
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LL | assert!(false, "{:03x} bla");
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| ^^^^^^^^^^^^
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LL | assert!(false, "{:03x} {test} bla");
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| ^^^^^^ ^^^^^^
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= note: this message is not used as a format string when given without arguments, but will be in a future Rust version
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help: add the missing argument(s)
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LL | assert!(false, "{:03x} bla", argument);
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| ^^^^^^^^^^
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LL | assert!(false, "{:03x} {test} bla", ...);
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| ^^^^^
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help: or add a "{}" format string to use the message literally
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LL | assert!(false, "{}", "{:03x} bla");
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LL | assert!(false, "{}", "{:03x} {test} bla");
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| ^^^^^
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warning: panic message contains a brace
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