src/tools/clippy/clippy_utils/src/diagnostics.rs

   1 //! Clippy wrappers around rustc's diagnostic functions.
   2 //!
   3 //! These functions are used by the `INTERNAL_METADATA_COLLECTOR` lint to collect the corresponding
   4 //! lint applicability. Please make sure that you update the `LINT_EMISSION_FUNCTIONS` variable in
   5 //! `clippy_lints::utils::internal_lints::metadata_collector` when a new function is added
   6 //! or renamed.
   7 //!
   8 //! Thank you!
   9 //! ~The `INTERNAL_METADATA_COLLECTOR` lint
  10
  11 use rustc_errors::{Applicability, DiagnosticBuilder};
  12 use rustc_hir::HirId;
  13 use rustc_lint::{LateContext, Lint, LintContext};
  14 use rustc_span::source_map::{MultiSpan, Span};
  15 use std::env;
  16
  17 fn docs_link(diag: &mut DiagnosticBuilder<'_>, lint: &'static Lint) {
  18     if env::var("CLIPPY_DISABLE_DOCS_LINKS").is_err() {
  19         if let Some(lint) = lint.name_lower().strip_prefix("clippy::") {
  20             diag.help(&format!(
  21                 "for further information visit https://rust-lang.github.io/rust-clippy/{}/index.html#{}",
  22                 &option_env!("RUST_RELEASE_NUM").map_or("master".to_string(), |n| {
  23                     // extract just major + minor version and ignore patch versions
  24                     format!("rust-{}", n.rsplitn(2, '.').nth(1).unwrap())
  25                 }),
  26                 lint
  27             ));
  28         }
  29     }
  30 }
  31
  32 /// Emit a basic lint message with a `msg` and a `span`.
  33 ///
  34 /// This is the most primitive of our lint emission methods and can
  35 /// be a good way to get a new lint started.
  36 ///
  37 /// Usually it's nicer to provide more context for lint messages.
  38 /// Be sure the output is understandable when you use this method.
  39 ///
  40 /// # Example
  41 ///
  42 /// ```ignore
  43 /// error: usage of mem::forget on Drop type
  44 ///   --> $DIR/mem_forget.rs:17:5
  45 ///    |
  46 /// 17 |     std::mem::forget(seven);
  47 ///    |     ^^^^^^^^^^^^^^^^^^^^^^^
  48 /// ```
  49 pub fn span_lint<T: LintContext>(cx: &T, lint: &'static Lint, sp: impl Into<MultiSpan>, msg: &str) {
  50     cx.struct_span_lint(lint, sp, |diag| {
  51         let mut diag = diag.build(msg);
  52         docs_link(&mut diag, lint);
  53         diag.emit();
  54     });
  55 }
  56
  57 /// Same as `span_lint` but with an extra `help` message.
  58 ///
  59 /// Use this if you want to provide some general help but
  60 /// can't provide a specific machine applicable suggestion.
  61 ///
  62 /// The `help` message can be optionally attached to a `Span`.
  63 ///
  64 /// If you change the signature, remember to update the internal lint `CollapsibleCalls`
  65 ///
  66 /// # Example
  67 ///
  68 /// ```ignore
  69 /// error: constant division of 0.0 with 0.0 will always result in NaN
  70 ///   --> $DIR/zero_div_zero.rs:6:25
  71 ///    |
  72 /// 6  |     let other_f64_nan = 0.0f64 / 0.0;
  73 ///    |                         ^^^^^^^^^^^^
  74 ///    |
  75 ///    = help: Consider using `f64::NAN` if you would like a constant representing NaN
  76 /// ```
  77 pub fn span_lint_and_help<'a, T: LintContext>(
  78     cx: &'a T,
  79     lint: &'static Lint,
  80     span: Span,
  81     msg: &str,
  82     help_span: Option<Span>,
  83     help: &str,
  84 ) {
  85     cx.struct_span_lint(lint, span, |diag| {
  86         let mut diag = diag.build(msg);
  87         if let Some(help_span) = help_span {
  88             diag.span_help(help_span, help);
  89         } else {
  90             diag.help(help);
  91         }
  92         docs_link(&mut diag, lint);
  93         diag.emit();
  94     });
  95 }
  96
  97 /// Like `span_lint` but with a `note` section instead of a `help` message.
  98 ///
  99 /// The `note` message is presented separately from the main lint message
 100 /// and is attached to a specific span:
 101 ///
 102 /// If you change the signature, remember to update the internal lint `CollapsibleCalls`
 103 ///
 104 /// # Example
 105 ///
 106 /// ```ignore
 107 /// error: calls to `std::mem::forget` with a reference instead of an owned value. Forgetting a reference does nothing.
 108 ///   --> $DIR/drop_forget_ref.rs:10:5
 109 ///    |
 110 /// 10 |     forget(&SomeStruct);
 111 ///    |     ^^^^^^^^^^^^^^^^^^^
 112 ///    |
 113 ///    = note: `-D clippy::forget-ref` implied by `-D warnings`
 114 /// note: argument has type &SomeStruct
 115 ///   --> $DIR/drop_forget_ref.rs:10:12
 116 ///    |
 117 /// 10 |     forget(&SomeStruct);
 118 ///    |            ^^^^^^^^^^^
 119 /// ```
 120 pub fn span_lint_and_note<'a, T: LintContext>(
 121     cx: &'a T,
 122     lint: &'static Lint,
 123     span: impl Into<MultiSpan>,
 124     msg: &str,
 125     note_span: Option<Span>,
 126     note: &str,
 127 ) {
 128     cx.struct_span_lint(lint, span, |diag| {
 129         let mut diag = diag.build(msg);
 130         if let Some(note_span) = note_span {
 131             diag.span_note(note_span, note);
 132         } else {
 133             diag.note(note);
 134         }
 135         docs_link(&mut diag, lint);
 136         diag.emit();
 137     });
 138 }
 139
 140 /// Like `span_lint` but allows to add notes, help and suggestions using a closure.
 141 ///
 142 /// If you need to customize your lint output a lot, use this function.
 143 /// If you change the signature, remember to update the internal lint `CollapsibleCalls`
 144 pub fn span_lint_and_then<C, S, F>(cx: &C, lint: &'static Lint, sp: S, msg: &str, f: F)
 145 where
 146     C: LintContext,
 147     S: Into<MultiSpan>,
 148     F: FnOnce(&mut DiagnosticBuilder<'_>),
 149 {
 150     cx.struct_span_lint(lint, sp, |diag| {
 151         let mut diag = diag.build(msg);
 152         f(&mut diag);
 153         docs_link(&mut diag, lint);
 154         diag.emit();
 155     });
 156 }
 157
 158 pub fn span_lint_hir(cx: &LateContext<'_>, lint: &'static Lint, hir_id: HirId, sp: Span, msg: &str) {
 159     cx.tcx.struct_span_lint_hir(lint, hir_id, sp, |diag| {
 160         let mut diag = diag.build(msg);
 161         docs_link(&mut diag, lint);
 162         diag.emit();
 163     });
 164 }
 165
 166 pub fn span_lint_hir_and_then(
 167     cx: &LateContext<'_>,
 168     lint: &'static Lint,
 169     hir_id: HirId,
 170     sp: impl Into<MultiSpan>,
 171     msg: &str,
 172     f: impl FnOnce(&mut DiagnosticBuilder<'_>),
 173 ) {
 174     cx.tcx.struct_span_lint_hir(lint, hir_id, sp, |diag| {
 175         let mut diag = diag.build(msg);
 176         f(&mut diag);
 177         docs_link(&mut diag, lint);
 178         diag.emit();
 179     });
 180 }
 181
 182 /// Add a span lint with a suggestion on how to fix it.
 183 ///
 184 /// These suggestions can be parsed by rustfix to allow it to automatically fix your code.
 185 /// In the example below, `help` is `"try"` and `sugg` is the suggested replacement `".any(|x| x >
 186 /// 2)"`.
 187 ///
 188 /// If you change the signature, remember to update the internal lint `CollapsibleCalls`
 189 ///
 190 /// # Example
 191 ///
 192 /// ```ignore
 193 /// error: This `.fold` can be more succinctly expressed as `.any`
 194 /// --> $DIR/methods.rs:390:13
 195 ///     |
 196 /// 390 |     let _ = (0..3).fold(false, |acc, x| acc || x > 2);
 197 ///     |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `.any(|x| x > 2)`
 198 ///     |
 199 ///     = note: `-D fold-any` implied by `-D warnings`
 200 /// ```
 201 #[cfg_attr(feature = "internal-lints", allow(clippy::collapsible_span_lint_calls))]
 202 pub fn span_lint_and_sugg<'a, T: LintContext>(
 203     cx: &'a T,
 204     lint: &'static Lint,
 205     sp: Span,
 206     msg: &str,
 207     help: &str,
 208     sugg: String,
 209     applicability: Applicability,
 210 ) {
 211     span_lint_and_then(cx, lint, sp, msg, |diag| {
 212         diag.span_suggestion(sp, help, sugg, applicability);
 213     });
 214 }
 215
 216 /// Create a suggestion made from several `span → replacement`.
 217 ///
 218 /// Note: in the JSON format (used by `compiletest_rs`), the help message will
 219 /// appear once per
 220 /// replacement. In human-readable format though, it only appears once before
 221 /// the whole suggestion.
 222 pub fn multispan_sugg<I>(diag: &mut DiagnosticBuilder<'_>, help_msg: &str, sugg: I)
 223 where
 224     I: IntoIterator<Item = (Span, String)>,
 225 {
 226     multispan_sugg_with_applicability(diag, help_msg, Applicability::Unspecified, sugg);
 227 }
 228
 229 /// Create a suggestion made from several `span → replacement`.
 230 ///
 231 /// rustfix currently doesn't support the automatic application of suggestions with
 232 /// multiple spans. This is tracked in issue [rustfix#141](https://github.com/rust-lang/rustfix/issues/141).
 233 /// Suggestions with multiple spans will be silently ignored.
 234 pub fn multispan_sugg_with_applicability<I>(
 235     diag: &mut DiagnosticBuilder<'_>,
 236     help_msg: &str,
 237     applicability: Applicability,
 238     sugg: I,
 239 ) where
 240     I: IntoIterator<Item = (Span, String)>,
 241 {
 242     diag.multipart_suggestion(help_msg, sugg.into_iter().collect(), applicability);
 243 }