src/tools/clippy/clippy_lints/src/utils/internal_lints.rs

   1 use clippy_utils::consts::{constant_simple, Constant};
   2 use clippy_utils::diagnostics::{span_lint, span_lint_and_help, span_lint_and_sugg, span_lint_and_then};
   3 use clippy_utils::source::snippet;
   4 use clippy_utils::ty::match_type;
   5 use clippy_utils::{
   6     is_else_clause, is_expn_of, is_expr_path_def_path, is_lint_allowed, match_def_path, method_calls, path_to_res,
   7     paths, SpanlessEq,
   8 };
   9 use if_chain::if_chain;
  10 use rustc_ast::ast::{Crate as AstCrate, ItemKind, LitKind, ModKind, NodeId};
  11 use rustc_ast::visit::FnKind;
  12 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
  13 use rustc_errors::Applicability;
  14 use rustc_hir as hir;
  15 use rustc_hir::def::{DefKind, Res};
  16 use rustc_hir::def_id::DefId;
  17 use rustc_hir::hir_id::CRATE_HIR_ID;
  18 use rustc_hir::intravisit::{NestedVisitorMap, Visitor};
  19 use rustc_hir::{
  20     BinOpKind, Block, Crate, Expr, ExprKind, HirId, Item, Local, MatchSource, MutTy, Mutability, Node, Path, Stmt,
  21     StmtKind, Ty, TyKind, UnOp,
  22 };
  23 use rustc_lint::{EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext};
  24 use rustc_middle::hir::map::Map;
  25 use rustc_middle::mir::interpret::ConstValue;
  26 use rustc_middle::ty;
  27 use rustc_session::{declare_lint_pass, declare_tool_lint, impl_lint_pass};
  28 use rustc_span::source_map::Spanned;
  29 use rustc_span::symbol::{Symbol, SymbolStr};
  30 use rustc_span::{BytePos, Span};
  31 use rustc_typeck::hir_ty_to_ty;
  32
  33 use std::borrow::{Borrow, Cow};
  34
  35 #[cfg(feature = "metadata-collector-lint")]
  36 pub mod metadata_collector;
  37
  38 declare_clippy_lint! {
  39     /// ### What it does
  40     /// Checks for various things we like to keep tidy in clippy.
  41     ///
  42     /// ### Why is this bad?
  43     /// We like to pretend we're an example of tidy code.
  44     ///
  45     /// ### Example
  46     /// Wrong ordering of the util::paths constants.
  47     pub CLIPPY_LINTS_INTERNAL,
  48     internal,
  49     "various things that will negatively affect your clippy experience"
  50 }
  51
  52 declare_clippy_lint! {
  53     /// ### What it does
  54     /// Ensures every lint is associated to a `LintPass`.
  55     ///
  56     /// ### Why is this bad?
  57     /// The compiler only knows lints via a `LintPass`. Without
  58     /// putting a lint to a `LintPass::get_lints()`'s return, the compiler will not
  59     /// know the name of the lint.
  60     ///
  61     /// ### Known problems
  62     /// Only checks for lints associated using the
  63     /// `declare_lint_pass!`, `impl_lint_pass!`, and `lint_array!` macros.
  64     ///
  65     /// ### Example
  66     /// ```rust,ignore
  67     /// declare_lint! { pub LINT_1, ... }
  68     /// declare_lint! { pub LINT_2, ... }
  69     /// declare_lint! { pub FORGOTTEN_LINT, ... }
  70     /// // ...
  71     /// declare_lint_pass!(Pass => [LINT_1, LINT_2]);
  72     /// // missing FORGOTTEN_LINT
  73     /// ```
  74     pub LINT_WITHOUT_LINT_PASS,
  75     internal,
  76     "declaring a lint without associating it in a LintPass"
  77 }
  78
  79 declare_clippy_lint! {
  80     /// ### What it does
  81     /// Checks for calls to `cx.span_lint*` and suggests to use the `utils::*`
  82     /// variant of the function.
  83     ///
  84     /// ### Why is this bad?
  85     /// The `utils::*` variants also add a link to the Clippy documentation to the
  86     /// warning/error messages.
  87     ///
  88     /// ### Example
  89     /// Bad:
  90     /// ```rust,ignore
  91     /// cx.span_lint(LINT_NAME, "message");
  92     /// ```
  93     ///
  94     /// Good:
  95     /// ```rust,ignore
  96     /// utils::span_lint(cx, LINT_NAME, "message");
  97     /// ```
  98     pub COMPILER_LINT_FUNCTIONS,
  99     internal,
 100     "usage of the lint functions of the compiler instead of the utils::* variant"
 101 }
 102
 103 declare_clippy_lint! {
 104     /// ### What it does
 105     /// Checks for calls to `cx.outer().expn_data()` and suggests to use
 106     /// the `cx.outer_expn_data()`
 107     ///
 108     /// ### Why is this bad?
 109     /// `cx.outer_expn_data()` is faster and more concise.
 110     ///
 111     /// ### Example
 112     /// Bad:
 113     /// ```rust,ignore
 114     /// expr.span.ctxt().outer().expn_data()
 115     /// ```
 116     ///
 117     /// Good:
 118     /// ```rust,ignore
 119     /// expr.span.ctxt().outer_expn_data()
 120     /// ```
 121     pub OUTER_EXPN_EXPN_DATA,
 122     internal,
 123     "using `cx.outer_expn().expn_data()` instead of `cx.outer_expn_data()`"
 124 }
 125
 126 declare_clippy_lint! {
 127     /// ### What it does
 128     /// Not an actual lint. This lint is only meant for testing our customized internal compiler
 129     /// error message by calling `panic`.
 130     ///
 131     /// ### Why is this bad?
 132     /// ICE in large quantities can damage your teeth
 133     ///
 134     /// ### Example
 135     /// Bad:
 136     /// ```rust,ignore
 137     /// 🍦🍦🍦🍦🍦
 138     /// ```
 139     pub PRODUCE_ICE,
 140     internal,
 141     "this message should not appear anywhere as we ICE before and don't emit the lint"
 142 }
 143
 144 declare_clippy_lint! {
 145     /// ### What it does
 146     /// Checks for cases of an auto-generated lint without an updated description,
 147     /// i.e. `default lint description`.
 148     ///
 149     /// ### Why is this bad?
 150     /// Indicates that the lint is not finished.
 151     ///
 152     /// ### Example
 153     /// Bad:
 154     /// ```rust,ignore
 155     /// declare_lint! { pub COOL_LINT, nursery, "default lint description" }
 156     /// ```
 157     ///
 158     /// Good:
 159     /// ```rust,ignore
 160     /// declare_lint! { pub COOL_LINT, nursery, "a great new lint" }
 161     /// ```
 162     pub DEFAULT_LINT,
 163     internal,
 164     "found 'default lint description' in a lint declaration"
 165 }
 166
 167 declare_clippy_lint! {
 168     /// ### What it does
 169     /// Lints `span_lint_and_then` function calls, where the
 170     /// closure argument has only one statement and that statement is a method
 171     /// call to `span_suggestion`, `span_help`, `span_note` (using the same
 172     /// span), `help` or `note`.
 173     ///
 174     /// These usages of `span_lint_and_then` should be replaced with one of the
 175     /// wrapper functions `span_lint_and_sugg`, span_lint_and_help`, or
 176     /// `span_lint_and_note`.
 177     ///
 178     /// ### Why is this bad?
 179     /// Using the wrapper `span_lint_and_*` functions, is more
 180     /// convenient, readable and less error prone.
 181     ///
 182     /// ### Example
 183     /// Bad:
 184     /// ```rust,ignore
 185     /// span_lint_and_then(cx, TEST_LINT, expr.span, lint_msg, |diag| {
 186     ///     diag.span_suggestion(
 187     ///         expr.span,
 188     ///         help_msg,
 189     ///         sugg.to_string(),
 190     ///         Applicability::MachineApplicable,
 191     ///     );
 192     /// });
 193     /// span_lint_and_then(cx, TEST_LINT, expr.span, lint_msg, |diag| {
 194     ///     diag.span_help(expr.span, help_msg);
 195     /// });
 196     /// span_lint_and_then(cx, TEST_LINT, expr.span, lint_msg, |diag| {
 197     ///     diag.help(help_msg);
 198     /// });
 199     /// span_lint_and_then(cx, TEST_LINT, expr.span, lint_msg, |diag| {
 200     ///     diag.span_note(expr.span, note_msg);
 201     /// });
 202     /// span_lint_and_then(cx, TEST_LINT, expr.span, lint_msg, |diag| {
 203     ///     diag.note(note_msg);
 204     /// });
 205     /// ```
 206     ///
 207     /// Good:
 208     /// ```rust,ignore
 209     /// span_lint_and_sugg(
 210     ///     cx,
 211     ///     TEST_LINT,
 212     ///     expr.span,
 213     ///     lint_msg,
 214     ///     help_msg,
 215     ///     sugg.to_string(),
 216     ///     Applicability::MachineApplicable,
 217     /// );
 218     /// span_lint_and_help(cx, TEST_LINT, expr.span, lint_msg, Some(expr.span), help_msg);
 219     /// span_lint_and_help(cx, TEST_LINT, expr.span, lint_msg, None, help_msg);
 220     /// span_lint_and_note(cx, TEST_LINT, expr.span, lint_msg, Some(expr.span), note_msg);
 221     /// span_lint_and_note(cx, TEST_LINT, expr.span, lint_msg, None, note_msg);
 222     /// ```
 223     pub COLLAPSIBLE_SPAN_LINT_CALLS,
 224     internal,
 225     "found collapsible `span_lint_and_then` calls"
 226 }
 227
 228 declare_clippy_lint! {
 229     /// ### What it does
 230     /// Checks for calls to `utils::match_type()` on a type diagnostic item
 231     /// and suggests to use `utils::is_type_diagnostic_item()` instead.
 232     ///
 233     /// ### Why is this bad?
 234     /// `utils::is_type_diagnostic_item()` does not require hardcoded paths.
 235     ///
 236     /// ### Example
 237     /// Bad:
 238     /// ```rust,ignore
 239     /// utils::match_type(cx, ty, &paths::VEC)
 240     /// ```
 241     ///
 242     /// Good:
 243     /// ```rust,ignore
 244     /// utils::is_type_diagnostic_item(cx, ty, sym::vec_type)
 245     /// ```
 246     pub MATCH_TYPE_ON_DIAGNOSTIC_ITEM,
 247     internal,
 248     "using `utils::match_type()` instead of `utils::is_type_diagnostic_item()`"
 249 }
 250
 251 declare_clippy_lint! {
 252     /// ### What it does
 253     /// Checks the paths module for invalid paths.
 254     ///
 255     /// ### Why is this bad?
 256     /// It indicates a bug in the code.
 257     ///
 258     /// ### Example
 259     /// None.
 260     pub INVALID_PATHS,
 261     internal,
 262     "invalid path"
 263 }
 264
 265 declare_clippy_lint! {
 266     /// ### What it does
 267     /// Checks for interning symbols that have already been pre-interned and defined as constants.
 268     ///
 269     /// ### Why is this bad?
 270     /// It's faster and easier to use the symbol constant.
 271     ///
 272     /// ### Example
 273     /// Bad:
 274     /// ```rust,ignore
 275     /// let _ = sym!(f32);
 276     /// ```
 277     ///
 278     /// Good:
 279     /// ```rust,ignore
 280     /// let _ = sym::f32;
 281     /// ```
 282     pub INTERNING_DEFINED_SYMBOL,
 283     internal,
 284     "interning a symbol that is pre-interned and defined as a constant"
 285 }
 286
 287 declare_clippy_lint! {
 288     /// ### What it does
 289     /// Checks for unnecessary conversion from Symbol to a string.
 290     ///
 291     /// ### Why is this bad?
 292     /// It's faster use symbols directly intead of strings.
 293     ///
 294     /// ### Example
 295     /// Bad:
 296     /// ```rust,ignore
 297     /// symbol.as_str() == "clippy";
 298     /// ```
 299     ///
 300     /// Good:
 301     /// ```rust,ignore
 302     /// symbol == sym::clippy;
 303     /// ```
 304     pub UNNECESSARY_SYMBOL_STR,
 305     internal,
 306     "unnecessary conversion between Symbol and string"
 307 }
 308
 309 declare_clippy_lint! {
 310     /// Finds unidiomatic usage of `if_chain!`
 311     pub IF_CHAIN_STYLE,
 312     internal,
 313     "non-idiomatic `if_chain!` usage"
 314 }
 315
 316 declare_lint_pass!(ClippyLintsInternal => [CLIPPY_LINTS_INTERNAL]);
 317
 318 impl EarlyLintPass for ClippyLintsInternal {
 319     fn check_crate(&mut self, cx: &EarlyContext<'_>, krate: &AstCrate) {
 320         if let Some(utils) = krate.items.iter().find(|item| item.ident.name.as_str() == "utils") {
 321             if let ItemKind::Mod(_, ModKind::Loaded(ref items, ..)) = utils.kind {
 322                 if let Some(paths) = items.iter().find(|item| item.ident.name.as_str() == "paths") {
 323                     if let ItemKind::Mod(_, ModKind::Loaded(ref items, ..)) = paths.kind {
 324                         let mut last_name: Option<SymbolStr> = None;
 325                         for item in items {
 326                             let name = item.ident.as_str();
 327                             if let Some(ref last_name) = last_name {
 328                                 if **last_name > *name {
 329                                     span_lint(
 330                                         cx,
 331                                         CLIPPY_LINTS_INTERNAL,
 332                                         item.span,
 333                                         "this constant should be before the previous constant due to lexical \
 334                                          ordering",
 335                                     );
 336                                 }
 337                             }
 338                             last_name = Some(name);
 339                         }
 340                     }
 341                 }
 342             }
 343         }
 344     }
 345 }
 346
 347 #[derive(Clone, Debug, Default)]
 348 pub struct LintWithoutLintPass {
 349     declared_lints: FxHashMap<Symbol, Span>,
 350     registered_lints: FxHashSet<Symbol>,
 351 }
 352
 353 impl_lint_pass!(LintWithoutLintPass => [DEFAULT_LINT, LINT_WITHOUT_LINT_PASS]);
 354
 355 impl<'tcx> LateLintPass<'tcx> for LintWithoutLintPass {
 356     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
 357         if is_lint_allowed(cx, DEFAULT_LINT, item.hir_id()) {
 358             return;
 359         }
 360
 361         if let hir::ItemKind::Static(ty, Mutability::Not, body_id) = item.kind {
 362             if is_lint_ref_type(cx, ty) {
 363                 let expr = &cx.tcx.hir().body(body_id).value;
 364                 if_chain! {
 365                     if let ExprKind::AddrOf(_, _, inner_exp) = expr.kind;
 366                     if let ExprKind::Struct(_, fields, _) = inner_exp.kind;
 367                     let field = fields
 368                         .iter()
 369                         .find(|f| f.ident.as_str() == "desc")
 370                         .expect("lints must have a description field");
 371                     if let ExprKind::Lit(Spanned {
 372                         node: LitKind::Str(ref sym, _),
 373                         ..
 374                     }) = field.expr.kind;
 375                     if sym.as_str() == "default lint description";
 376
 377                     then {
 378                         span_lint(
 379                             cx,
 380                             DEFAULT_LINT,
 381                             item.span,
 382                             &format!("the lint `{}` has the default lint description", item.ident.name),
 383                         );
 384                     }
 385                 }
 386                 self.declared_lints.insert(item.ident.name, item.span);
 387             }
 388         } else if is_expn_of(item.span, "impl_lint_pass").is_some()
 389             || is_expn_of(item.span, "declare_lint_pass").is_some()
 390         {
 391             if let hir::ItemKind::Impl(hir::Impl {
 392                 of_trait: None,
 393                 items: impl_item_refs,
 394                 ..
 395             }) = item.kind
 396             {
 397                 let mut collector = LintCollector {
 398                     output: &mut self.registered_lints,
 399                     cx,
 400                 };
 401                 let body_id = cx.tcx.hir().body_owned_by(
 402                     impl_item_refs
 403                         .iter()
 404                         .find(|iiref| iiref.ident.as_str() == "get_lints")
 405                         .expect("LintPass needs to implement get_lints")
 406                         .id
 407                         .hir_id(),
 408                 );
 409                 collector.visit_expr(&cx.tcx.hir().body(body_id).value);
 410             }
 411         }
 412     }
 413
 414     fn check_crate_post(&mut self, cx: &LateContext<'tcx>, _: &'tcx Crate<'_>) {
 415         if is_lint_allowed(cx, LINT_WITHOUT_LINT_PASS, CRATE_HIR_ID) {
 416             return;
 417         }
 418
 419         for (lint_name, &lint_span) in &self.declared_lints {
 420             // When using the `declare_tool_lint!` macro, the original `lint_span`'s
 421             // file points to "<rustc macros>".
 422             // `compiletest-rs` thinks that's an error in a different file and
 423             // just ignores it. This causes the test in compile-fail/lint_pass
 424             // not able to capture the error.
 425             // Therefore, we need to climb the macro expansion tree and find the
 426             // actual span that invoked `declare_tool_lint!`:
 427             let lint_span = lint_span.ctxt().outer_expn_data().call_site;
 428
 429             if !self.registered_lints.contains(lint_name) {
 430                 span_lint(
 431                     cx,
 432                     LINT_WITHOUT_LINT_PASS,
 433                     lint_span,
 434                     &format!("the lint `{}` is not added to any `LintPass`", lint_name),
 435                 );
 436             }
 437         }
 438     }
 439 }
 440
 441 fn is_lint_ref_type<'tcx>(cx: &LateContext<'tcx>, ty: &Ty<'_>) -> bool {
 442     if let TyKind::Rptr(
 443         _,
 444         MutTy {
 445             ty: inner,
 446             mutbl: Mutability::Not,
 447         },
 448     ) = ty.kind
 449     {
 450         if let TyKind::Path(ref path) = inner.kind {
 451             if let Res::Def(DefKind::Struct, def_id) = cx.qpath_res(path, inner.hir_id) {
 452                 return match_def_path(cx, def_id, &paths::LINT);
 453             }
 454         }
 455     }
 456
 457     false
 458 }
 459
 460 struct LintCollector<'a, 'tcx> {
 461     output: &'a mut FxHashSet<Symbol>,
 462     cx: &'a LateContext<'tcx>,
 463 }
 464
 465 impl<'a, 'tcx> Visitor<'tcx> for LintCollector<'a, 'tcx> {
 466     type Map = Map<'tcx>;
 467
 468     fn visit_path(&mut self, path: &'tcx Path<'_>, _: HirId) {
 469         if path.segments.len() == 1 {
 470             self.output.insert(path.segments[0].ident.name);
 471         }
 472     }
 473
 474     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
 475         NestedVisitorMap::All(self.cx.tcx.hir())
 476     }
 477 }
 478
 479 #[derive(Clone, Default)]
 480 pub struct CompilerLintFunctions {
 481     map: FxHashMap<&'static str, &'static str>,
 482 }
 483
 484 impl CompilerLintFunctions {
 485     #[must_use]
 486     pub fn new() -> Self {
 487         let mut map = FxHashMap::default();
 488         map.insert("span_lint", "utils::span_lint");
 489         map.insert("struct_span_lint", "utils::span_lint");
 490         map.insert("lint", "utils::span_lint");
 491         map.insert("span_lint_note", "utils::span_lint_and_note");
 492         map.insert("span_lint_help", "utils::span_lint_and_help");
 493         Self { map }
 494     }
 495 }
 496
 497 impl_lint_pass!(CompilerLintFunctions => [COMPILER_LINT_FUNCTIONS]);
 498
 499 impl<'tcx> LateLintPass<'tcx> for CompilerLintFunctions {
 500     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
 501         if is_lint_allowed(cx, COMPILER_LINT_FUNCTIONS, expr.hir_id) {
 502             return;
 503         }
 504
 505         if_chain! {
 506             if let ExprKind::MethodCall(path, _, args, _) = expr.kind;
 507             let fn_name = path.ident;
 508             if let Some(sugg) = self.map.get(&*fn_name.as_str());
 509             let ty = cx.typeck_results().expr_ty(&args[0]).peel_refs();
 510             if match_type(cx, ty, &paths::EARLY_CONTEXT)
 511                 || match_type(cx, ty, &paths::LATE_CONTEXT);
 512             then {
 513                 span_lint_and_help(
 514                     cx,
 515                     COMPILER_LINT_FUNCTIONS,
 516                     path.ident.span,
 517                     "usage of a compiler lint function",
 518                     None,
 519                     &format!("please use the Clippy variant of this function: `{}`", sugg),
 520                 );
 521             }
 522         }
 523     }
 524 }
 525
 526 declare_lint_pass!(OuterExpnDataPass => [OUTER_EXPN_EXPN_DATA]);
 527
 528 impl<'tcx> LateLintPass<'tcx> for OuterExpnDataPass {
 529     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
 530         if is_lint_allowed(cx, OUTER_EXPN_EXPN_DATA, expr.hir_id) {
 531             return;
 532         }
 533
 534         let (method_names, arg_lists, spans) = method_calls(expr, 2);
 535         let method_names: Vec<SymbolStr> = method_names.iter().map(|s| s.as_str()).collect();
 536         let method_names: Vec<&str> = method_names.iter().map(|s| &**s).collect();
 537         if_chain! {
 538             if let ["expn_data", "outer_expn"] = method_names.as_slice();
 539             let args = arg_lists[1];
 540             if args.len() == 1;
 541             let self_arg = &args[0];
 542             let self_ty = cx.typeck_results().expr_ty(self_arg).peel_refs();
 543             if match_type(cx, self_ty, &paths::SYNTAX_CONTEXT);
 544             then {
 545                 span_lint_and_sugg(
 546                     cx,
 547                     OUTER_EXPN_EXPN_DATA,
 548                     spans[1].with_hi(expr.span.hi()),
 549                     "usage of `outer_expn().expn_data()`",
 550                     "try",
 551                     "outer_expn_data()".to_string(),
 552                     Applicability::MachineApplicable,
 553                 );
 554             }
 555         }
 556     }
 557 }
 558
 559 declare_lint_pass!(ProduceIce => [PRODUCE_ICE]);
 560
 561 impl EarlyLintPass for ProduceIce {
 562     fn check_fn(&mut self, _: &EarlyContext<'_>, fn_kind: FnKind<'_>, _: Span, _: NodeId) {
 563         if is_trigger_fn(fn_kind) {
 564             panic!("Would you like some help with that?");
 565         }
 566     }
 567 }
 568
 569 fn is_trigger_fn(fn_kind: FnKind<'_>) -> bool {
 570     match fn_kind {
 571         FnKind::Fn(_, ident, ..) => ident.name.as_str() == "it_looks_like_you_are_trying_to_kill_clippy",
 572         FnKind::Closure(..) => false,
 573     }
 574 }
 575
 576 declare_lint_pass!(CollapsibleCalls => [COLLAPSIBLE_SPAN_LINT_CALLS]);
 577
 578 impl<'tcx> LateLintPass<'tcx> for CollapsibleCalls {
 579     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
 580         if is_lint_allowed(cx, COLLAPSIBLE_SPAN_LINT_CALLS, expr.hir_id) {
 581             return;
 582         }
 583
 584         if_chain! {
 585             if let ExprKind::Call(func, and_then_args) = expr.kind;
 586             if is_expr_path_def_path(cx, func, &["clippy_utils", "diagnostics", "span_lint_and_then"]);
 587             if and_then_args.len() == 5;
 588             if let ExprKind::Closure(_, _, body_id, _, _) = &and_then_args[4].kind;
 589             let body = cx.tcx.hir().body(*body_id);
 590             if let ExprKind::Block(block, _) = &body.value.kind;
 591             let stmts = &block.stmts;
 592             if stmts.len() == 1 && block.expr.is_none();
 593             if let StmtKind::Semi(only_expr) = &stmts[0].kind;
 594             if let ExprKind::MethodCall(ps, _, span_call_args, _) = &only_expr.kind;
 595             then {
 596                 let and_then_snippets = get_and_then_snippets(cx, and_then_args);
 597                 let mut sle = SpanlessEq::new(cx).deny_side_effects();
 598                 match &*ps.ident.as_str() {
 599                     "span_suggestion" if sle.eq_expr(&and_then_args[2], &span_call_args[1]) => {
 600                         suggest_suggestion(cx, expr, &and_then_snippets, &span_suggestion_snippets(cx, span_call_args));
 601                     },
 602                     "span_help" if sle.eq_expr(&and_then_args[2], &span_call_args[1]) => {
 603                         let help_snippet = snippet(cx, span_call_args[2].span, r#""...""#);
 604                         suggest_help(cx, expr, &and_then_snippets, help_snippet.borrow(), true);
 605                     },
 606                     "span_note" if sle.eq_expr(&and_then_args[2], &span_call_args[1]) => {
 607                         let note_snippet = snippet(cx, span_call_args[2].span, r#""...""#);
 608                         suggest_note(cx, expr, &and_then_snippets, note_snippet.borrow(), true);
 609                     },
 610                     "help" => {
 611                         let help_snippet = snippet(cx, span_call_args[1].span, r#""...""#);
 612                         suggest_help(cx, expr, &and_then_snippets, help_snippet.borrow(), false);
 613                     }
 614                     "note" => {
 615                         let note_snippet = snippet(cx, span_call_args[1].span, r#""...""#);
 616                         suggest_note(cx, expr, &and_then_snippets, note_snippet.borrow(), false);
 617                     }
 618                     _  => (),
 619                 }
 620             }
 621         }
 622     }
 623 }
 624
 625 struct AndThenSnippets<'a> {
 626     cx: Cow<'a, str>,
 627     lint: Cow<'a, str>,
 628     span: Cow<'a, str>,
 629     msg: Cow<'a, str>,
 630 }
 631
 632 fn get_and_then_snippets<'a, 'hir>(cx: &LateContext<'_>, and_then_snippets: &'hir [Expr<'hir>]) -> AndThenSnippets<'a> {
 633     let cx_snippet = snippet(cx, and_then_snippets[0].span, "cx");
 634     let lint_snippet = snippet(cx, and_then_snippets[1].span, "..");
 635     let span_snippet = snippet(cx, and_then_snippets[2].span, "span");
 636     let msg_snippet = snippet(cx, and_then_snippets[3].span, r#""...""#);
 637
 638     AndThenSnippets {
 639         cx: cx_snippet,
 640         lint: lint_snippet,
 641         span: span_snippet,
 642         msg: msg_snippet,
 643     }
 644 }
 645
 646 struct SpanSuggestionSnippets<'a> {
 647     help: Cow<'a, str>,
 648     sugg: Cow<'a, str>,
 649     applicability: Cow<'a, str>,
 650 }
 651
 652 fn span_suggestion_snippets<'a, 'hir>(
 653     cx: &LateContext<'_>,
 654     span_call_args: &'hir [Expr<'hir>],
 655 ) -> SpanSuggestionSnippets<'a> {
 656     let help_snippet = snippet(cx, span_call_args[2].span, r#""...""#);
 657     let sugg_snippet = snippet(cx, span_call_args[3].span, "..");
 658     let applicability_snippet = snippet(cx, span_call_args[4].span, "Applicability::MachineApplicable");
 659
 660     SpanSuggestionSnippets {
 661         help: help_snippet,
 662         sugg: sugg_snippet,
 663         applicability: applicability_snippet,
 664     }
 665 }
 666
 667 fn suggest_suggestion(
 668     cx: &LateContext<'_>,
 669     expr: &Expr<'_>,
 670     and_then_snippets: &AndThenSnippets<'_>,
 671     span_suggestion_snippets: &SpanSuggestionSnippets<'_>,
 672 ) {
 673     span_lint_and_sugg(
 674         cx,
 675         COLLAPSIBLE_SPAN_LINT_CALLS,
 676         expr.span,
 677         "this call is collapsible",
 678         "collapse into",
 679         format!(
 680             "span_lint_and_sugg({}, {}, {}, {}, {}, {}, {})",
 681             and_then_snippets.cx,
 682             and_then_snippets.lint,
 683             and_then_snippets.span,
 684             and_then_snippets.msg,
 685             span_suggestion_snippets.help,
 686             span_suggestion_snippets.sugg,
 687             span_suggestion_snippets.applicability
 688         ),
 689         Applicability::MachineApplicable,
 690     );
 691 }
 692
 693 fn suggest_help(
 694     cx: &LateContext<'_>,
 695     expr: &Expr<'_>,
 696     and_then_snippets: &AndThenSnippets<'_>,
 697     help: &str,
 698     with_span: bool,
 699 ) {
 700     let option_span = if with_span {
 701         format!("Some({})", and_then_snippets.span)
 702     } else {
 703         "None".to_string()
 704     };
 705
 706     span_lint_and_sugg(
 707         cx,
 708         COLLAPSIBLE_SPAN_LINT_CALLS,
 709         expr.span,
 710         "this call is collapsible",
 711         "collapse into",
 712         format!(
 713             "span_lint_and_help({}, {}, {}, {}, {}, {})",
 714             and_then_snippets.cx,
 715             and_then_snippets.lint,
 716             and_then_snippets.span,
 717             and_then_snippets.msg,
 718             &option_span,
 719             help
 720         ),
 721         Applicability::MachineApplicable,
 722     );
 723 }
 724
 725 fn suggest_note(
 726     cx: &LateContext<'_>,
 727     expr: &Expr<'_>,
 728     and_then_snippets: &AndThenSnippets<'_>,
 729     note: &str,
 730     with_span: bool,
 731 ) {
 732     let note_span = if with_span {
 733         format!("Some({})", and_then_snippets.span)
 734     } else {
 735         "None".to_string()
 736     };
 737
 738     span_lint_and_sugg(
 739         cx,
 740         COLLAPSIBLE_SPAN_LINT_CALLS,
 741         expr.span,
 742         "this call is collspible",
 743         "collapse into",
 744         format!(
 745             "span_lint_and_note({}, {}, {}, {}, {}, {})",
 746             and_then_snippets.cx,
 747             and_then_snippets.lint,
 748             and_then_snippets.span,
 749             and_then_snippets.msg,
 750             note_span,
 751             note
 752         ),
 753         Applicability::MachineApplicable,
 754     );
 755 }
 756
 757 declare_lint_pass!(MatchTypeOnDiagItem => [MATCH_TYPE_ON_DIAGNOSTIC_ITEM]);
 758
 759 impl<'tcx> LateLintPass<'tcx> for MatchTypeOnDiagItem {
 760     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
 761         if is_lint_allowed(cx, MATCH_TYPE_ON_DIAGNOSTIC_ITEM, expr.hir_id) {
 762             return;
 763         }
 764
 765         if_chain! {
 766             // Check if this is a call to utils::match_type()
 767             if let ExprKind::Call(fn_path, [context, ty, ty_path]) = expr.kind;
 768             if is_expr_path_def_path(cx, fn_path, &["clippy_utils", "ty", "match_type"]);
 769             // Extract the path to the matched type
 770             if let Some(segments) = path_to_matched_type(cx, ty_path);
 771             let segments: Vec<&str> = segments.iter().map(|sym| &**sym).collect();
 772             if let Some(ty_did) = path_to_res(cx, &segments[..]).opt_def_id();
 773             // Check if the matched type is a diagnostic item
 774             let diag_items = cx.tcx.diagnostic_items(ty_did.krate);
 775             if let Some(item_name) = diag_items.iter().find_map(|(k, v)| if *v == ty_did { Some(k) } else { None });
 776             then {
 777                 // TODO: check paths constants from external crates.
 778                 let cx_snippet = snippet(cx, context.span, "_");
 779                 let ty_snippet = snippet(cx, ty.span, "_");
 780
 781                 span_lint_and_sugg(
 782                     cx,
 783                     MATCH_TYPE_ON_DIAGNOSTIC_ITEM,
 784                     expr.span,
 785                     "usage of `clippy_utils::ty::match_type()` on a type diagnostic item",
 786                     "try",
 787                     format!("clippy_utils::ty::is_type_diagnostic_item({}, {}, sym::{})", cx_snippet, ty_snippet, item_name),
 788                     Applicability::MaybeIncorrect,
 789                 );
 790             }
 791         }
 792     }
 793 }
 794
 795 fn path_to_matched_type(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option<Vec<SymbolStr>> {
 796     use rustc_hir::ItemKind;
 797
 798     match &expr.kind {
 799         ExprKind::AddrOf(.., expr) => return path_to_matched_type(cx, expr),
 800         ExprKind::Path(qpath) => match cx.qpath_res(qpath, expr.hir_id) {
 801             Res::Local(hir_id) => {
 802                 let parent_id = cx.tcx.hir().get_parent_node(hir_id);
 803                 if let Some(Node::Local(local)) = cx.tcx.hir().find(parent_id) {
 804                     if let Some(init) = local.init {
 805                         return path_to_matched_type(cx, init);
 806                     }
 807                 }
 808             },
 809             Res::Def(DefKind::Const | DefKind::Static, def_id) => {
 810                 if let Some(Node::Item(item)) = cx.tcx.hir().get_if_local(def_id) {
 811                     if let ItemKind::Const(.., body_id) | ItemKind::Static(.., body_id) = item.kind {
 812                         let body = cx.tcx.hir().body(body_id);
 813                         return path_to_matched_type(cx, &body.value);
 814                     }
 815                 }
 816             },
 817             _ => {},
 818         },
 819         ExprKind::Array(exprs) => {
 820             let segments: Vec<SymbolStr> = exprs
 821                 .iter()
 822                 .filter_map(|expr| {
 823                     if let ExprKind::Lit(lit) = &expr.kind {
 824                         if let LitKind::Str(sym, _) = lit.node {
 825                             return Some(sym.as_str());
 826                         }
 827                     }
 828
 829                     None
 830                 })
 831                 .collect();
 832
 833             if segments.len() == exprs.len() {
 834                 return Some(segments);
 835             }
 836         },
 837         _ => {},
 838     }
 839
 840     None
 841 }
 842
 843 // This is not a complete resolver for paths. It works on all the paths currently used in the paths
 844 // module.  That's all it does and all it needs to do.
 845 pub fn check_path(cx: &LateContext<'_>, path: &[&str]) -> bool {
 846     if path_to_res(cx, path) != Res::Err {
 847         return true;
 848     }
 849
 850     // Some implementations can't be found by `path_to_res`, particularly inherent
 851     // implementations of native types. Check lang items.
 852     let path_syms: Vec<_> = path.iter().map(|p| Symbol::intern(p)).collect();
 853     let lang_items = cx.tcx.lang_items();
 854     for item_def_id in lang_items.items().iter().flatten() {
 855         let lang_item_path = cx.get_def_path(*item_def_id);
 856         if path_syms.starts_with(&lang_item_path) {
 857             if let [item] = &path_syms[lang_item_path.len()..] {
 858                 for child in cx.tcx.item_children(*item_def_id) {
 859                     if child.ident.name == *item {
 860                         return true;
 861                     }
 862                 }
 863             }
 864         }
 865     }
 866
 867     false
 868 }
 869
 870 declare_lint_pass!(InvalidPaths => [INVALID_PATHS]);
 871
 872 impl<'tcx> LateLintPass<'tcx> for InvalidPaths {
 873     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
 874         let local_def_id = &cx.tcx.parent_module(item.hir_id());
 875         let mod_name = &cx.tcx.item_name(local_def_id.to_def_id());
 876         if_chain! {
 877             if mod_name.as_str() == "paths";
 878             if let hir::ItemKind::Const(ty, body_id) = item.kind;
 879             let ty = hir_ty_to_ty(cx.tcx, ty);
 880             if let ty::Array(el_ty, _) = &ty.kind();
 881             if let ty::Ref(_, el_ty, _) = &el_ty.kind();
 882             if el_ty.is_str();
 883             let body = cx.tcx.hir().body(body_id);
 884             let typeck_results = cx.tcx.typeck_body(body_id);
 885             if let Some(Constant::Vec(path)) = constant_simple(cx, typeck_results, &body.value);
 886             let path: Vec<&str> = path.iter().map(|x| {
 887                     if let Constant::Str(s) = x {
 888                         s.as_str()
 889                     } else {
 890                         // We checked the type of the constant above
 891                         unreachable!()
 892                     }
 893                 }).collect();
 894             if !check_path(cx, &path[..]);
 895             then {
 896                 span_lint(cx, CLIPPY_LINTS_INTERNAL, item.span, "invalid path");
 897             }
 898         }
 899     }
 900 }
 901
 902 #[derive(Default)]
 903 pub struct InterningDefinedSymbol {
 904     // Maps the symbol value to the constant DefId.
 905     symbol_map: FxHashMap<u32, DefId>,
 906 }
 907
 908 impl_lint_pass!(InterningDefinedSymbol => [INTERNING_DEFINED_SYMBOL, UNNECESSARY_SYMBOL_STR]);
 909
 910 impl<'tcx> LateLintPass<'tcx> for InterningDefinedSymbol {
 911     fn check_crate(&mut self, cx: &LateContext<'_>, _: &Crate<'_>) {
 912         if !self.symbol_map.is_empty() {
 913             return;
 914         }
 915
 916         for &module in &[&paths::KW_MODULE, &paths::SYM_MODULE] {
 917             if let Some(def_id) = path_to_res(cx, module).opt_def_id() {
 918                 for item in cx.tcx.item_children(def_id).iter() {
 919                     if_chain! {
 920                         if let Res::Def(DefKind::Const, item_def_id) = item.res;
 921                         let ty = cx.tcx.type_of(item_def_id);
 922                         if match_type(cx, ty, &paths::SYMBOL);
 923                         if let Ok(ConstValue::Scalar(value)) = cx.tcx.const_eval_poly(item_def_id);
 924                         if let Ok(value) = value.to_u32();
 925                         then {
 926                             self.symbol_map.insert(value, item_def_id);
 927                         }
 928                     }
 929                 }
 930             }
 931         }
 932     }
 933
 934     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
 935         if_chain! {
 936             if let ExprKind::Call(func, [arg]) = &expr.kind;
 937             if let ty::FnDef(def_id, _) = cx.typeck_results().expr_ty(func).kind();
 938             if match_def_path(cx, *def_id, &paths::SYMBOL_INTERN);
 939             if let Some(Constant::Str(arg)) = constant_simple(cx, cx.typeck_results(), arg);
 940             let value = Symbol::intern(&arg).as_u32();
 941             if let Some(&def_id) = self.symbol_map.get(&value);
 942             then {
 943                 span_lint_and_sugg(
 944                     cx,
 945                     INTERNING_DEFINED_SYMBOL,
 946                     is_expn_of(expr.span, "sym").unwrap_or(expr.span),
 947                     "interning a defined symbol",
 948                     "try",
 949                     cx.tcx.def_path_str(def_id),
 950                     Applicability::MachineApplicable,
 951                 );
 952             }
 953         }
 954         if let ExprKind::Binary(op, left, right) = expr.kind {
 955             if matches!(op.node, BinOpKind::Eq | BinOpKind::Ne) {
 956                 let data = [
 957                     (left, self.symbol_str_expr(left, cx)),
 958                     (right, self.symbol_str_expr(right, cx)),
 959                 ];
 960                 match data {
 961                     // both operands are a symbol string
 962                     [(_, Some(left)), (_, Some(right))] => {
 963                         span_lint_and_sugg(
 964                             cx,
 965                             UNNECESSARY_SYMBOL_STR,
 966                             expr.span,
 967                             "unnecessary `Symbol` to string conversion",
 968                             "try",
 969                             format!(
 970                                 "{} {} {}",
 971                                 left.as_symbol_snippet(cx),
 972                                 op.node.as_str(),
 973                                 right.as_symbol_snippet(cx),
 974                             ),
 975                             Applicability::MachineApplicable,
 976                         );
 977                     },
 978                     // one of the operands is a symbol string
 979                     [(expr, Some(symbol)), _] | [_, (expr, Some(symbol))] => {
 980                         // creating an owned string for comparison
 981                         if matches!(symbol, SymbolStrExpr::Expr { is_to_owned: true, .. }) {
 982                             span_lint_and_sugg(
 983                                 cx,
 984                                 UNNECESSARY_SYMBOL_STR,
 985                                 expr.span,
 986                                 "unnecessary string allocation",
 987                                 "try",
 988                                 format!("{}.as_str()", symbol.as_symbol_snippet(cx)),
 989                                 Applicability::MachineApplicable,
 990                             );
 991                         }
 992                     },
 993                     // nothing found
 994                     [(_, None), (_, None)] => {},
 995                 }
 996             }
 997         }
 998     }
 999 }
1000
1001 impl InterningDefinedSymbol {
1002     fn symbol_str_expr<'tcx>(&self, expr: &'tcx Expr<'tcx>, cx: &LateContext<'tcx>) -> Option<SymbolStrExpr<'tcx>> {
1003         static IDENT_STR_PATHS: &[&[&str]] = &[&paths::IDENT_AS_STR, &paths::TO_STRING_METHOD];
1004         static SYMBOL_STR_PATHS: &[&[&str]] = &[
1005             &paths::SYMBOL_AS_STR,
1006             &paths::SYMBOL_TO_IDENT_STRING,
1007             &paths::TO_STRING_METHOD,
1008         ];
1009         // SymbolStr might be de-referenced: `&*symbol.as_str()`
1010         let call = if_chain! {
1011             if let ExprKind::AddrOf(_, _, e) = expr.kind;
1012             if let ExprKind::Unary(UnOp::Deref, e) = e.kind;
1013             then { e } else { expr }
1014         };
1015         if_chain! {
1016             // is a method call
1017             if let ExprKind::MethodCall(_, _, [item], _) = call.kind;
1018             if let Some(did) = cx.typeck_results().type_dependent_def_id(call.hir_id);
1019             let ty = cx.typeck_results().expr_ty(item);
1020             // ...on either an Ident or a Symbol
1021             if let Some(is_ident) = if match_type(cx, ty, &paths::SYMBOL) {
1022                 Some(false)
1023             } else if match_type(cx, ty, &paths::IDENT) {
1024                 Some(true)
1025             } else {
1026                 None
1027             };
1028             // ...which converts it to a string
1029             let paths = if is_ident { IDENT_STR_PATHS } else { SYMBOL_STR_PATHS };
1030             if let Some(path) = paths.iter().find(|path| match_def_path(cx, did, path));
1031             then {
1032                 let is_to_owned = path.last().unwrap().ends_with("string");
1033                 return Some(SymbolStrExpr::Expr {
1034                     item,
1035                     is_ident,
1036                     is_to_owned,
1037                 });
1038             }
1039         }
1040         // is a string constant
1041         if let Some(Constant::Str(s)) = constant_simple(cx, cx.typeck_results(), expr) {
1042             let value = Symbol::intern(&s).as_u32();
1043             // ...which matches a symbol constant
1044             if let Some(&def_id) = self.symbol_map.get(&value) {
1045                 return Some(SymbolStrExpr::Const(def_id));
1046             }
1047         }
1048         None
1049     }
1050 }
1051
1052 enum SymbolStrExpr<'tcx> {
1053     /// a string constant with a corresponding symbol constant
1054     Const(DefId),
1055     /// a "symbol to string" expression like `symbol.as_str()`
1056     Expr {
1057         /// part that evaluates to `Symbol` or `Ident`
1058         item: &'tcx Expr<'tcx>,
1059         is_ident: bool,
1060         /// whether an owned `String` is created like `to_ident_string()`
1061         is_to_owned: bool,
1062     },
1063 }
1064
1065 impl<'tcx> SymbolStrExpr<'tcx> {
1066     /// Returns a snippet that evaluates to a `Symbol` and is const if possible
1067     fn as_symbol_snippet(&self, cx: &LateContext<'_>) -> Cow<'tcx, str> {
1068         match *self {
1069             Self::Const(def_id) => cx.tcx.def_path_str(def_id).into(),
1070             Self::Expr { item, is_ident, .. } => {
1071                 let mut snip = snippet(cx, item.span.source_callsite(), "..");
1072                 if is_ident {
1073                     // get `Ident.name`
1074                     snip.to_mut().push_str(".name");
1075                 }
1076                 snip
1077             },
1078         }
1079     }
1080 }
1081
1082 declare_lint_pass!(IfChainStyle => [IF_CHAIN_STYLE]);
1083
1084 impl<'tcx> LateLintPass<'tcx> for IfChainStyle {
1085     fn check_block(&mut self, cx: &LateContext<'tcx>, block: &'tcx hir::Block<'_>) {
1086         let (local, after, if_chain_span) = if_chain! {
1087             if let [Stmt { kind: StmtKind::Local(local), .. }, after @ ..] = block.stmts;
1088             if let Some(if_chain_span) = is_expn_of(block.span, "if_chain");
1089             then { (local, after, if_chain_span) } else { return }
1090         };
1091         if is_first_if_chain_expr(cx, block.hir_id, if_chain_span) {
1092             span_lint(
1093                 cx,
1094                 IF_CHAIN_STYLE,
1095                 if_chain_local_span(cx, local, if_chain_span),
1096                 "`let` expression should be above the `if_chain!`",
1097             );
1098         } else if local.span.ctxt() == block.span.ctxt() && is_if_chain_then(after, block.expr, if_chain_span) {
1099             span_lint(
1100                 cx,
1101                 IF_CHAIN_STYLE,
1102                 if_chain_local_span(cx, local, if_chain_span),
1103                 "`let` expression should be inside `then { .. }`",
1104             );
1105         }
1106     }
1107
1108     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
1109         let (cond, then, els) = match expr.kind {
1110             ExprKind::If(cond, then, els) => (Some(cond), then, els.is_some()),
1111             ExprKind::Match(
1112                 _,
1113                 [arm, ..],
1114                 MatchSource::IfLetDesugar {
1115                     contains_else_clause: els,
1116                 },
1117             ) => (None, arm.body, els),
1118             _ => return,
1119         };
1120         let then_block = match then.kind {
1121             ExprKind::Block(block, _) => block,
1122             _ => return,
1123         };
1124         let if_chain_span = is_expn_of(expr.span, "if_chain");
1125         if !els {
1126             check_nested_if_chains(cx, expr, then_block, if_chain_span);
1127         }
1128         let if_chain_span = match if_chain_span {
1129             None => return,
1130             Some(span) => span,
1131         };
1132         // check for `if a && b;`
1133         if_chain! {
1134             if let Some(cond) = cond;
1135             if let ExprKind::Binary(op, _, _) = cond.kind;
1136             if op.node == BinOpKind::And;
1137             if cx.sess().source_map().is_multiline(cond.span);
1138             then {
1139                 span_lint(cx, IF_CHAIN_STYLE, cond.span, "`if a && b;` should be `if a; if b;`");
1140             }
1141         }
1142         if is_first_if_chain_expr(cx, expr.hir_id, if_chain_span)
1143             && is_if_chain_then(then_block.stmts, then_block.expr, if_chain_span)
1144         {
1145             span_lint(cx, IF_CHAIN_STYLE, expr.span, "`if_chain!` only has one `if`");
1146         }
1147     }
1148 }
1149
1150 fn check_nested_if_chains(
1151     cx: &LateContext<'_>,
1152     if_expr: &Expr<'_>,
1153     then_block: &Block<'_>,
1154     if_chain_span: Option<Span>,
1155 ) {
1156     #[rustfmt::skip]
1157     let (head, tail) = match *then_block {
1158         Block { stmts, expr: Some(tail), .. } => (stmts, tail),
1159         Block {
1160             stmts: &[
1161                 ref head @ ..,
1162                 Stmt { kind: StmtKind::Expr(tail) | StmtKind::Semi(tail), .. }
1163             ],
1164             ..
1165         } => (head, tail),
1166         _ => return,
1167     };
1168     if_chain! {
1169         if matches!(tail.kind,
1170             ExprKind::If(_, _, None)
1171             | ExprKind::Match(.., MatchSource::IfLetDesugar { contains_else_clause: false }));
1172         let sm = cx.sess().source_map();
1173         if head
1174             .iter()
1175             .all(|stmt| matches!(stmt.kind, StmtKind::Local(..)) && !sm.is_multiline(stmt.span));
1176         if if_chain_span.is_some() || !is_else_clause(cx.tcx, if_expr);
1177         then {} else { return }
1178     }
1179     let (span, msg) = match (if_chain_span, is_expn_of(tail.span, "if_chain")) {
1180         (None, Some(_)) => (if_expr.span, "this `if` can be part of the inner `if_chain!`"),
1181         (Some(_), None) => (tail.span, "this `if` can be part of the outer `if_chain!`"),
1182         (Some(a), Some(b)) if a != b => (b, "this `if_chain!` can be merged with the outer `if_chain!`"),
1183         _ => return,
1184     };
1185     span_lint_and_then(cx, IF_CHAIN_STYLE, span, msg, |diag| {
1186         let (span, msg) = match head {
1187             [] => return,
1188             [stmt] => (stmt.span, "this `let` statement can also be in the `if_chain!`"),
1189             [a, .., b] => (
1190                 a.span.to(b.span),
1191                 "these `let` statements can also be in the `if_chain!`",
1192             ),
1193         };
1194         diag.span_help(span, msg);
1195     });
1196 }
1197
1198 fn is_first_if_chain_expr(cx: &LateContext<'_>, hir_id: HirId, if_chain_span: Span) -> bool {
1199     cx.tcx
1200         .hir()
1201         .parent_iter(hir_id)
1202         .find(|(_, node)| {
1203             #[rustfmt::skip]
1204             !matches!(node, Node::Expr(Expr { kind: ExprKind::Block(..), .. }) | Node::Stmt(_))
1205         })
1206         .map_or(false, |(id, _)| {
1207             is_expn_of(cx.tcx.hir().span(id), "if_chain") != Some(if_chain_span)
1208         })
1209 }
1210
1211 /// Checks a trailing slice of statements and expression of a `Block` to see if they are part
1212 /// of the `then {..}` portion of an `if_chain!`
1213 fn is_if_chain_then(stmts: &[Stmt<'_>], expr: Option<&Expr<'_>>, if_chain_span: Span) -> bool {
1214     let span = if let [stmt, ..] = stmts {
1215         stmt.span
1216     } else if let Some(expr) = expr {
1217         expr.span
1218     } else {
1219         // empty `then {}`
1220         return true;
1221     };
1222     is_expn_of(span, "if_chain").map_or(true, |span| span != if_chain_span)
1223 }
1224
1225 /// Creates a `Span` for `let x = ..;` in an `if_chain!` call.
1226 fn if_chain_local_span(cx: &LateContext<'_>, local: &Local<'_>, if_chain_span: Span) -> Span {
1227     let mut span = local.pat.span;
1228     if let Some(init) = local.init {
1229         span = span.to(init.span);
1230     }
1231     span.adjust(if_chain_span.ctxt().outer_expn());
1232     let sm = cx.sess().source_map();
1233     let span = sm.span_extend_to_prev_str(span, "let", false);
1234     let span = sm.span_extend_to_next_char(span, ';', false);
1235     Span::new(span.lo() - BytePos(3), span.hi() + BytePos(1), span.ctxt())
1236 }