src/tools/clippy/clippy_utils/src/sugg.rs

   1 //! Contains utility functions to generate suggestions.
   2 #![deny(clippy::missing_docs_in_private_items)]
   3
   4 use crate::higher;
   5 use crate::source::{snippet, snippet_opt, snippet_with_macro_callsite};
   6 use rustc_ast::util::parser::AssocOp;
   7 use rustc_ast::{ast, token};
   8 use rustc_ast_pretty::pprust::token_kind_to_string;
   9 use rustc_errors::Applicability;
  10 use rustc_hir as hir;
  11 use rustc_lint::{EarlyContext, LateContext, LintContext};
  12 use rustc_span::source_map::{CharPos, Span};
  13 use rustc_span::{BytePos, Pos};
  14 use std::borrow::Cow;
  15 use std::convert::TryInto;
  16 use std::fmt::Display;
  17 use std::ops::{Add, Neg, Not, Sub};
  18
  19 /// A helper type to build suggestion correctly handling parenthesis.
  20 #[derive(Clone, PartialEq)]
  21 pub enum Sugg<'a> {
  22     /// An expression that never needs parenthesis such as `1337` or `[0; 42]`.
  23     NonParen(Cow<'a, str>),
  24     /// An expression that does not fit in other variants.
  25     MaybeParen(Cow<'a, str>),
  26     /// A binary operator expression, including `as`-casts and explicit type
  27     /// coercion.
  28     BinOp(AssocOp, Cow<'a, str>),
  29 }
  30
  31 /// Literal constant `0`, for convenience.
  32 pub const ZERO: Sugg<'static> = Sugg::NonParen(Cow::Borrowed("0"));
  33 /// Literal constant `1`, for convenience.
  34 pub const ONE: Sugg<'static> = Sugg::NonParen(Cow::Borrowed("1"));
  35 /// a constant represents an empty string, for convenience.
  36 pub const EMPTY: Sugg<'static> = Sugg::NonParen(Cow::Borrowed(""));
  37
  38 impl Display for Sugg<'_> {
  39     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
  40         match *self {
  41             Sugg::NonParen(ref s) | Sugg::MaybeParen(ref s) | Sugg::BinOp(_, ref s) => s.fmt(f),
  42         }
  43     }
  44 }
  45
  46 #[allow(clippy::wrong_self_convention)] // ok, because of the function `as_ty` method
  47 impl<'a> Sugg<'a> {
  48     /// Prepare a suggestion from an expression.
  49     pub fn hir_opt(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option<Self> {
  50         snippet_opt(cx, expr.span).map(|snippet| {
  51             let snippet = Cow::Owned(snippet);
  52             Self::hir_from_snippet(expr, snippet)
  53         })
  54     }
  55
  56     /// Convenience function around `hir_opt` for suggestions with a default
  57     /// text.
  58     pub fn hir(cx: &LateContext<'_>, expr: &hir::Expr<'_>, default: &'a str) -> Self {
  59         Self::hir_opt(cx, expr).unwrap_or(Sugg::NonParen(Cow::Borrowed(default)))
  60     }
  61
  62     /// Same as `hir`, but it adapts the applicability level by following rules:
  63     ///
  64     /// - Applicability level `Unspecified` will never be changed.
  65     /// - If the span is inside a macro, change the applicability level to `MaybeIncorrect`.
  66     /// - If the default value is used and the applicability level is `MachineApplicable`, change it
  67     ///   to
  68     /// `HasPlaceholders`
  69     pub fn hir_with_applicability(
  70         cx: &LateContext<'_>,
  71         expr: &hir::Expr<'_>,
  72         default: &'a str,
  73         applicability: &mut Applicability,
  74     ) -> Self {
  75         if *applicability != Applicability::Unspecified && expr.span.from_expansion() {
  76             *applicability = Applicability::MaybeIncorrect;
  77         }
  78         Self::hir_opt(cx, expr).unwrap_or_else(|| {
  79             if *applicability == Applicability::MachineApplicable {
  80                 *applicability = Applicability::HasPlaceholders;
  81             }
  82             Sugg::NonParen(Cow::Borrowed(default))
  83         })
  84     }
  85
  86     /// Same as `hir`, but will use the pre expansion span if the `expr` was in a macro.
  87     pub fn hir_with_macro_callsite(cx: &LateContext<'_>, expr: &hir::Expr<'_>, default: &'a str) -> Self {
  88         let snippet = snippet_with_macro_callsite(cx, expr.span, default);
  89
  90         Self::hir_from_snippet(expr, snippet)
  91     }
  92
  93     /// Generate a suggestion for an expression with the given snippet. This is used by the `hir_*`
  94     /// function variants of `Sugg`, since these use different snippet functions.
  95     fn hir_from_snippet(expr: &hir::Expr<'_>, snippet: Cow<'a, str>) -> Self {
  96         if let Some(range) = higher::range(expr) {
  97             let op = match range.limits {
  98                 ast::RangeLimits::HalfOpen => AssocOp::DotDot,
  99                 ast::RangeLimits::Closed => AssocOp::DotDotEq,
 100             };
 101             return Sugg::BinOp(op, snippet);
 102         }
 103
 104         match expr.kind {
 105             hir::ExprKind::AddrOf(..)
 106             | hir::ExprKind::Box(..)
 107             | hir::ExprKind::If(..)
 108             | hir::ExprKind::Closure(..)
 109             | hir::ExprKind::Unary(..)
 110             | hir::ExprKind::Match(..) => Sugg::MaybeParen(snippet),
 111             hir::ExprKind::Continue(..)
 112             | hir::ExprKind::Yield(..)
 113             | hir::ExprKind::Array(..)
 114             | hir::ExprKind::Block(..)
 115             | hir::ExprKind::Break(..)
 116             | hir::ExprKind::Call(..)
 117             | hir::ExprKind::Field(..)
 118             | hir::ExprKind::Index(..)
 119             | hir::ExprKind::InlineAsm(..)
 120             | hir::ExprKind::LlvmInlineAsm(..)
 121             | hir::ExprKind::ConstBlock(..)
 122             | hir::ExprKind::Lit(..)
 123             | hir::ExprKind::Loop(..)
 124             | hir::ExprKind::MethodCall(..)
 125             | hir::ExprKind::Path(..)
 126             | hir::ExprKind::Repeat(..)
 127             | hir::ExprKind::Ret(..)
 128             | hir::ExprKind::Struct(..)
 129             | hir::ExprKind::Tup(..)
 130             | hir::ExprKind::DropTemps(_)
 131             | hir::ExprKind::Err => Sugg::NonParen(snippet),
 132             hir::ExprKind::Assign(..) => Sugg::BinOp(AssocOp::Assign, snippet),
 133             hir::ExprKind::AssignOp(op, ..) => Sugg::BinOp(hirbinop2assignop(op), snippet),
 134             hir::ExprKind::Binary(op, ..) => Sugg::BinOp(AssocOp::from_ast_binop(higher::binop(op.node)), snippet),
 135             hir::ExprKind::Cast(..) => Sugg::BinOp(AssocOp::As, snippet),
 136             hir::ExprKind::Type(..) => Sugg::BinOp(AssocOp::Colon, snippet),
 137         }
 138     }
 139
 140     /// Prepare a suggestion from an expression.
 141     pub fn ast(cx: &EarlyContext<'_>, expr: &ast::Expr, default: &'a str) -> Self {
 142         use rustc_ast::ast::RangeLimits;
 143
 144         let snippet = if expr.span.from_expansion() {
 145             snippet_with_macro_callsite(cx, expr.span, default)
 146         } else {
 147             snippet(cx, expr.span, default)
 148         };
 149
 150         match expr.kind {
 151             ast::ExprKind::AddrOf(..)
 152             | ast::ExprKind::Box(..)
 153             | ast::ExprKind::Closure(..)
 154             | ast::ExprKind::If(..)
 155             | ast::ExprKind::Let(..)
 156             | ast::ExprKind::Unary(..)
 157             | ast::ExprKind::Match(..) => Sugg::MaybeParen(snippet),
 158             ast::ExprKind::Async(..)
 159             | ast::ExprKind::Block(..)
 160             | ast::ExprKind::Break(..)
 161             | ast::ExprKind::Call(..)
 162             | ast::ExprKind::Continue(..)
 163             | ast::ExprKind::Yield(..)
 164             | ast::ExprKind::Field(..)
 165             | ast::ExprKind::ForLoop(..)
 166             | ast::ExprKind::Index(..)
 167             | ast::ExprKind::InlineAsm(..)
 168             | ast::ExprKind::LlvmInlineAsm(..)
 169             | ast::ExprKind::ConstBlock(..)
 170             | ast::ExprKind::Lit(..)
 171             | ast::ExprKind::Loop(..)
 172             | ast::ExprKind::MacCall(..)
 173             | ast::ExprKind::MethodCall(..)
 174             | ast::ExprKind::Paren(..)
 175             | ast::ExprKind::Underscore
 176             | ast::ExprKind::Path(..)
 177             | ast::ExprKind::Repeat(..)
 178             | ast::ExprKind::Ret(..)
 179             | ast::ExprKind::Struct(..)
 180             | ast::ExprKind::Try(..)
 181             | ast::ExprKind::TryBlock(..)
 182             | ast::ExprKind::Tup(..)
 183             | ast::ExprKind::Array(..)
 184             | ast::ExprKind::While(..)
 185             | ast::ExprKind::Await(..)
 186             | ast::ExprKind::Err => Sugg::NonParen(snippet),
 187             ast::ExprKind::Range(.., RangeLimits::HalfOpen) => Sugg::BinOp(AssocOp::DotDot, snippet),
 188             ast::ExprKind::Range(.., RangeLimits::Closed) => Sugg::BinOp(AssocOp::DotDotEq, snippet),
 189             ast::ExprKind::Assign(..) => Sugg::BinOp(AssocOp::Assign, snippet),
 190             ast::ExprKind::AssignOp(op, ..) => Sugg::BinOp(astbinop2assignop(op), snippet),
 191             ast::ExprKind::Binary(op, ..) => Sugg::BinOp(AssocOp::from_ast_binop(op.node), snippet),
 192             ast::ExprKind::Cast(..) => Sugg::BinOp(AssocOp::As, snippet),
 193             ast::ExprKind::Type(..) => Sugg::BinOp(AssocOp::Colon, snippet),
 194         }
 195     }
 196
 197     /// Convenience method to create the `<lhs> && <rhs>` suggestion.
 198     pub fn and(self, rhs: &Self) -> Sugg<'static> {
 199         make_binop(ast::BinOpKind::And, &self, rhs)
 200     }
 201
 202     /// Convenience method to create the `<lhs> & <rhs>` suggestion.
 203     pub fn bit_and(self, rhs: &Self) -> Sugg<'static> {
 204         make_binop(ast::BinOpKind::BitAnd, &self, rhs)
 205     }
 206
 207     /// Convenience method to create the `<lhs> as <rhs>` suggestion.
 208     pub fn as_ty<R: Display>(self, rhs: R) -> Sugg<'static> {
 209         make_assoc(AssocOp::As, &self, &Sugg::NonParen(rhs.to_string().into()))
 210     }
 211
 212     /// Convenience method to create the `&<expr>` suggestion.
 213     pub fn addr(self) -> Sugg<'static> {
 214         make_unop("&", self)
 215     }
 216
 217     /// Convenience method to create the `&mut <expr>` suggestion.
 218     pub fn mut_addr(self) -> Sugg<'static> {
 219         make_unop("&mut ", self)
 220     }
 221
 222     /// Convenience method to create the `*<expr>` suggestion.
 223     pub fn deref(self) -> Sugg<'static> {
 224         make_unop("*", self)
 225     }
 226
 227     /// Convenience method to create the `&*<expr>` suggestion. Currently this
 228     /// is needed because `sugg.deref().addr()` produces an unnecessary set of
 229     /// parentheses around the deref.
 230     pub fn addr_deref(self) -> Sugg<'static> {
 231         make_unop("&*", self)
 232     }
 233
 234     /// Convenience method to create the `&mut *<expr>` suggestion. Currently
 235     /// this is needed because `sugg.deref().mut_addr()` produces an unnecessary
 236     /// set of parentheses around the deref.
 237     pub fn mut_addr_deref(self) -> Sugg<'static> {
 238         make_unop("&mut *", self)
 239     }
 240
 241     /// Convenience method to transform suggestion into a return call
 242     pub fn make_return(self) -> Sugg<'static> {
 243         Sugg::NonParen(Cow::Owned(format!("return {}", self)))
 244     }
 245
 246     /// Convenience method to transform suggestion into a block
 247     /// where the suggestion is a trailing expression
 248     pub fn blockify(self) -> Sugg<'static> {
 249         Sugg::NonParen(Cow::Owned(format!("{{ {} }}", self)))
 250     }
 251
 252     /// Convenience method to create the `<lhs>..<rhs>` or `<lhs>...<rhs>`
 253     /// suggestion.
 254     #[allow(dead_code)]
 255     pub fn range(self, end: &Self, limit: ast::RangeLimits) -> Sugg<'static> {
 256         match limit {
 257             ast::RangeLimits::HalfOpen => make_assoc(AssocOp::DotDot, &self, end),
 258             ast::RangeLimits::Closed => make_assoc(AssocOp::DotDotEq, &self, end),
 259         }
 260     }
 261
 262     /// Adds parenthesis to any expression that might need them. Suitable to the
 263     /// `self` argument of a method call
 264     /// (e.g., to build `bar.foo()` or `(1 + 2).foo()`).
 265     pub fn maybe_par(self) -> Self {
 266         match self {
 267             Sugg::NonParen(..) => self,
 268             // `(x)` and `(x).y()` both don't need additional parens.
 269             Sugg::MaybeParen(sugg) => {
 270                 if has_enclosing_paren(&sugg) {
 271                     Sugg::MaybeParen(sugg)
 272                 } else {
 273                     Sugg::NonParen(format!("({})", sugg).into())
 274                 }
 275             },
 276             Sugg::BinOp(_, sugg) => {
 277                 if has_enclosing_paren(&sugg) {
 278                     Sugg::NonParen(sugg)
 279                 } else {
 280                     Sugg::NonParen(format!("({})", sugg).into())
 281                 }
 282             },
 283         }
 284     }
 285 }
 286
 287 /// Return `true` if `sugg` is enclosed in parenthesis.
 288 fn has_enclosing_paren(sugg: impl AsRef<str>) -> bool {
 289     let mut chars = sugg.as_ref().chars();
 290     if let Some('(') = chars.next() {
 291         let mut depth = 1;
 292         while let Some(c) = chars.next() {
 293             if c == '(' {
 294                 depth += 1;
 295             } else if c == ')' {
 296                 depth -= 1;
 297             }
 298             if depth == 0 {
 299                 break;
 300             }
 301         }
 302         chars.next().is_none()
 303     } else {
 304         false
 305     }
 306 }
 307
 308 // Copied from the rust standart library, and then edited
 309 macro_rules! forward_binop_impls_to_ref {
 310     (impl $imp:ident, $method:ident for $t:ty, type Output = $o:ty) => {
 311         impl $imp<$t> for &$t {
 312             type Output = $o;
 313
 314             fn $method(self, other: $t) -> $o {
 315                 $imp::$method(self, &other)
 316             }
 317         }
 318
 319         impl $imp<&$t> for $t {
 320             type Output = $o;
 321
 322             fn $method(self, other: &$t) -> $o {
 323                 $imp::$method(&self, other)
 324             }
 325         }
 326
 327         impl $imp for $t {
 328             type Output = $o;
 329
 330             fn $method(self, other: $t) -> $o {
 331                 $imp::$method(&self, &other)
 332             }
 333         }
 334     };
 335 }
 336
 337 impl Add for &Sugg<'_> {
 338     type Output = Sugg<'static>;
 339     fn add(self, rhs: &Sugg<'_>) -> Sugg<'static> {
 340         make_binop(ast::BinOpKind::Add, self, rhs)
 341     }
 342 }
 343
 344 impl Sub for &Sugg<'_> {
 345     type Output = Sugg<'static>;
 346     fn sub(self, rhs: &Sugg<'_>) -> Sugg<'static> {
 347         make_binop(ast::BinOpKind::Sub, self, rhs)
 348     }
 349 }
 350
 351 forward_binop_impls_to_ref!(impl Add, add for Sugg<'_>, type Output = Sugg<'static>);
 352 forward_binop_impls_to_ref!(impl Sub, sub for Sugg<'_>, type Output = Sugg<'static>);
 353
 354 impl Neg for Sugg<'_> {
 355     type Output = Sugg<'static>;
 356     fn neg(self) -> Sugg<'static> {
 357         make_unop("-", self)
 358     }
 359 }
 360
 361 impl Not for Sugg<'_> {
 362     type Output = Sugg<'static>;
 363     fn not(self) -> Sugg<'static> {
 364         make_unop("!", self)
 365     }
 366 }
 367
 368 /// Helper type to display either `foo` or `(foo)`.
 369 struct ParenHelper<T> {
 370     /// `true` if parentheses are needed.
 371     paren: bool,
 372     /// The main thing to display.
 373     wrapped: T,
 374 }
 375
 376 impl<T> ParenHelper<T> {
 377     /// Builds a `ParenHelper`.
 378     fn new(paren: bool, wrapped: T) -> Self {
 379         Self { paren, wrapped }
 380     }
 381 }
 382
 383 impl<T: Display> Display for ParenHelper<T> {
 384     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
 385         if self.paren {
 386             write!(f, "({})", self.wrapped)
 387         } else {
 388             self.wrapped.fmt(f)
 389         }
 390     }
 391 }
 392
 393 /// Builds the string for `<op><expr>` adding parenthesis when necessary.
 394 ///
 395 /// For convenience, the operator is taken as a string because all unary
 396 /// operators have the same
 397 /// precedence.
 398 pub fn make_unop(op: &str, expr: Sugg<'_>) -> Sugg<'static> {
 399     Sugg::MaybeParen(format!("{}{}", op, expr.maybe_par()).into())
 400 }
 401
 402 /// Builds the string for `<lhs> <op> <rhs>` adding parenthesis when necessary.
 403 ///
 404 /// Precedence of shift operator relative to other arithmetic operation is
 405 /// often confusing so
 406 /// parenthesis will always be added for a mix of these.
 407 pub fn make_assoc(op: AssocOp, lhs: &Sugg<'_>, rhs: &Sugg<'_>) -> Sugg<'static> {
 408     /// Returns `true` if the operator is a shift operator `<<` or `>>`.
 409     fn is_shift(op: AssocOp) -> bool {
 410         matches!(op, AssocOp::ShiftLeft | AssocOp::ShiftRight)
 411     }
 412
 413     /// Returns `true` if the operator is a arithmetic operator
 414     /// (i.e., `+`, `-`, `*`, `/`, `%`).
 415     fn is_arith(op: AssocOp) -> bool {
 416         matches!(
 417             op,
 418             AssocOp::Add | AssocOp::Subtract | AssocOp::Multiply | AssocOp::Divide | AssocOp::Modulus
 419         )
 420     }
 421
 422     /// Returns `true` if the operator `op` needs parenthesis with the operator
 423     /// `other` in the direction `dir`.
 424     fn needs_paren(op: AssocOp, other: AssocOp, dir: Associativity) -> bool {
 425         other.precedence() < op.precedence()
 426             || (other.precedence() == op.precedence()
 427                 && ((op != other && associativity(op) != dir)
 428                     || (op == other && associativity(op) != Associativity::Both)))
 429             || is_shift(op) && is_arith(other)
 430             || is_shift(other) && is_arith(op)
 431     }
 432
 433     let lhs_paren = if let Sugg::BinOp(lop, _) = *lhs {
 434         needs_paren(op, lop, Associativity::Left)
 435     } else {
 436         false
 437     };
 438
 439     let rhs_paren = if let Sugg::BinOp(rop, _) = *rhs {
 440         needs_paren(op, rop, Associativity::Right)
 441     } else {
 442         false
 443     };
 444
 445     let lhs = ParenHelper::new(lhs_paren, lhs);
 446     let rhs = ParenHelper::new(rhs_paren, rhs);
 447     let sugg = match op {
 448         AssocOp::Add
 449         | AssocOp::BitAnd
 450         | AssocOp::BitOr
 451         | AssocOp::BitXor
 452         | AssocOp::Divide
 453         | AssocOp::Equal
 454         | AssocOp::Greater
 455         | AssocOp::GreaterEqual
 456         | AssocOp::LAnd
 457         | AssocOp::LOr
 458         | AssocOp::Less
 459         | AssocOp::LessEqual
 460         | AssocOp::Modulus
 461         | AssocOp::Multiply
 462         | AssocOp::NotEqual
 463         | AssocOp::ShiftLeft
 464         | AssocOp::ShiftRight
 465         | AssocOp::Subtract => format!(
 466             "{} {} {}",
 467             lhs,
 468             op.to_ast_binop().expect("Those are AST ops").to_string(),
 469             rhs
 470         ),
 471         AssocOp::Assign => format!("{} = {}", lhs, rhs),
 472         AssocOp::AssignOp(op) => format!("{} {}= {}", lhs, token_kind_to_string(&token::BinOp(op)), rhs),
 473         AssocOp::As => format!("{} as {}", lhs, rhs),
 474         AssocOp::DotDot => format!("{}..{}", lhs, rhs),
 475         AssocOp::DotDotEq => format!("{}..={}", lhs, rhs),
 476         AssocOp::Colon => format!("{}: {}", lhs, rhs),
 477     };
 478
 479     Sugg::BinOp(op, sugg.into())
 480 }
 481
 482 /// Convenience wrapper around `make_assoc` and `AssocOp::from_ast_binop`.
 483 pub fn make_binop(op: ast::BinOpKind, lhs: &Sugg<'_>, rhs: &Sugg<'_>) -> Sugg<'static> {
 484     make_assoc(AssocOp::from_ast_binop(op), lhs, rhs)
 485 }
 486
 487 #[derive(PartialEq, Eq, Clone, Copy)]
 488 /// Operator associativity.
 489 enum Associativity {
 490     /// The operator is both left-associative and right-associative.
 491     Both,
 492     /// The operator is left-associative.
 493     Left,
 494     /// The operator is not associative.
 495     None,
 496     /// The operator is right-associative.
 497     Right,
 498 }
 499
 500 /// Returns the associativity/fixity of an operator. The difference with
 501 /// `AssocOp::fixity` is that an operator can be both left and right associative
 502 /// (such as `+`: `a + b + c == (a + b) + c == a + (b + c)`.
 503 ///
 504 /// Chained `as` and explicit `:` type coercion never need inner parenthesis so
 505 /// they are considered
 506 /// associative.
 507 #[must_use]
 508 fn associativity(op: AssocOp) -> Associativity {
 509     use rustc_ast::util::parser::AssocOp::{
 510         Add, As, Assign, AssignOp, BitAnd, BitOr, BitXor, Colon, Divide, DotDot, DotDotEq, Equal, Greater,
 511         GreaterEqual, LAnd, LOr, Less, LessEqual, Modulus, Multiply, NotEqual, ShiftLeft, ShiftRight, Subtract,
 512     };
 513
 514     match op {
 515         Assign | AssignOp(_) => Associativity::Right,
 516         Add | BitAnd | BitOr | BitXor | LAnd | LOr | Multiply | As | Colon => Associativity::Both,
 517         Divide | Equal | Greater | GreaterEqual | Less | LessEqual | Modulus | NotEqual | ShiftLeft | ShiftRight
 518         | Subtract => Associativity::Left,
 519         DotDot | DotDotEq => Associativity::None,
 520     }
 521 }
 522
 523 /// Converts a `hir::BinOp` to the corresponding assigning binary operator.
 524 fn hirbinop2assignop(op: hir::BinOp) -> AssocOp {
 525     use rustc_ast::token::BinOpToken::{And, Caret, Minus, Or, Percent, Plus, Shl, Shr, Slash, Star};
 526
 527     AssocOp::AssignOp(match op.node {
 528         hir::BinOpKind::Add => Plus,
 529         hir::BinOpKind::BitAnd => And,
 530         hir::BinOpKind::BitOr => Or,
 531         hir::BinOpKind::BitXor => Caret,
 532         hir::BinOpKind::Div => Slash,
 533         hir::BinOpKind::Mul => Star,
 534         hir::BinOpKind::Rem => Percent,
 535         hir::BinOpKind::Shl => Shl,
 536         hir::BinOpKind::Shr => Shr,
 537         hir::BinOpKind::Sub => Minus,
 538
 539         hir::BinOpKind::And
 540         | hir::BinOpKind::Eq
 541         | hir::BinOpKind::Ge
 542         | hir::BinOpKind::Gt
 543         | hir::BinOpKind::Le
 544         | hir::BinOpKind::Lt
 545         | hir::BinOpKind::Ne
 546         | hir::BinOpKind::Or => panic!("This operator does not exist"),
 547     })
 548 }
 549
 550 /// Converts an `ast::BinOp` to the corresponding assigning binary operator.
 551 fn astbinop2assignop(op: ast::BinOp) -> AssocOp {
 552     use rustc_ast::ast::BinOpKind::{
 553         Add, And, BitAnd, BitOr, BitXor, Div, Eq, Ge, Gt, Le, Lt, Mul, Ne, Or, Rem, Shl, Shr, Sub,
 554     };
 555     use rustc_ast::token::BinOpToken;
 556
 557     AssocOp::AssignOp(match op.node {
 558         Add => BinOpToken::Plus,
 559         BitAnd => BinOpToken::And,
 560         BitOr => BinOpToken::Or,
 561         BitXor => BinOpToken::Caret,
 562         Div => BinOpToken::Slash,
 563         Mul => BinOpToken::Star,
 564         Rem => BinOpToken::Percent,
 565         Shl => BinOpToken::Shl,
 566         Shr => BinOpToken::Shr,
 567         Sub => BinOpToken::Minus,
 568         And | Eq | Ge | Gt | Le | Lt | Ne | Or => panic!("This operator does not exist"),
 569     })
 570 }
 571
 572 /// Returns the indentation before `span` if there are nothing but `[ \t]`
 573 /// before it on its line.
 574 fn indentation<T: LintContext>(cx: &T, span: Span) -> Option<String> {
 575     let lo = cx.sess().source_map().lookup_char_pos(span.lo());
 576     lo.file
 577         .get_line(lo.line - 1 /* line numbers in `Loc` are 1-based */)
 578         .and_then(|line| {
 579             if let Some((pos, _)) = line.char_indices().find(|&(_, c)| c != ' ' && c != '\t') {
 580                 // We can mix char and byte positions here because we only consider `[ \t]`.
 581                 if lo.col == CharPos(pos) {
 582                     Some(line[..pos].into())
 583                 } else {
 584                     None
 585                 }
 586             } else {
 587                 None
 588             }
 589         })
 590 }
 591
 592 /// Convenience extension trait for `DiagnosticBuilder`.
 593 pub trait DiagnosticBuilderExt<T: LintContext> {
 594     /// Suggests to add an attribute to an item.
 595     ///
 596     /// Correctly handles indentation of the attribute and item.
 597     ///
 598     /// # Example
 599     ///
 600     /// ```rust,ignore
 601     /// diag.suggest_item_with_attr(cx, item, "#[derive(Default)]");
 602     /// ```
 603     fn suggest_item_with_attr<D: Display + ?Sized>(
 604         &mut self,
 605         cx: &T,
 606         item: Span,
 607         msg: &str,
 608         attr: &D,
 609         applicability: Applicability,
 610     );
 611
 612     /// Suggest to add an item before another.
 613     ///
 614     /// The item should not be indented (except for inner indentation).
 615     ///
 616     /// # Example
 617     ///
 618     /// ```rust,ignore
 619     /// diag.suggest_prepend_item(cx, item,
 620     /// "fn foo() {
 621     ///     bar();
 622     /// }");
 623     /// ```
 624     fn suggest_prepend_item(&mut self, cx: &T, item: Span, msg: &str, new_item: &str, applicability: Applicability);
 625
 626     /// Suggest to completely remove an item.
 627     ///
 628     /// This will remove an item and all following whitespace until the next non-whitespace
 629     /// character. This should work correctly if item is on the same indentation level as the
 630     /// following item.
 631     ///
 632     /// # Example
 633     ///
 634     /// ```rust,ignore
 635     /// diag.suggest_remove_item(cx, item, "remove this")
 636     /// ```
 637     fn suggest_remove_item(&mut self, cx: &T, item: Span, msg: &str, applicability: Applicability);
 638 }
 639
 640 impl<T: LintContext> DiagnosticBuilderExt<T> for rustc_errors::DiagnosticBuilder<'_> {
 641     fn suggest_item_with_attr<D: Display + ?Sized>(
 642         &mut self,
 643         cx: &T,
 644         item: Span,
 645         msg: &str,
 646         attr: &D,
 647         applicability: Applicability,
 648     ) {
 649         if let Some(indent) = indentation(cx, item) {
 650             let span = item.with_hi(item.lo());
 651
 652             self.span_suggestion(span, msg, format!("{}\n{}", attr, indent), applicability);
 653         }
 654     }
 655
 656     fn suggest_prepend_item(&mut self, cx: &T, item: Span, msg: &str, new_item: &str, applicability: Applicability) {
 657         if let Some(indent) = indentation(cx, item) {
 658             let span = item.with_hi(item.lo());
 659
 660             let mut first = true;
 661             let new_item = new_item
 662                 .lines()
 663                 .map(|l| {
 664                     if first {
 665                         first = false;
 666                         format!("{}\n", l)
 667                     } else {
 668                         format!("{}{}\n", indent, l)
 669                     }
 670                 })
 671                 .collect::<String>();
 672
 673             self.span_suggestion(span, msg, format!("{}\n{}", new_item, indent), applicability);
 674         }
 675     }
 676
 677     fn suggest_remove_item(&mut self, cx: &T, item: Span, msg: &str, applicability: Applicability) {
 678         let mut remove_span = item;
 679         let hi = cx.sess().source_map().next_point(remove_span).hi();
 680         let fmpos = cx.sess().source_map().lookup_byte_offset(hi);
 681
 682         if let Some(ref src) = fmpos.sf.src {
 683             let non_whitespace_offset = src[fmpos.pos.to_usize()..].find(|c| c != ' ' && c != '\t' && c != '\n');
 684
 685             if let Some(non_whitespace_offset) = non_whitespace_offset {
 686                 remove_span = remove_span
 687                     .with_hi(remove_span.hi() + BytePos(non_whitespace_offset.try_into().expect("offset too large")))
 688             }
 689         }
 690
 691         self.span_suggestion(remove_span, msg, String::new(), applicability);
 692     }
 693 }
 694
 695 #[cfg(test)]
 696 mod test {
 697     use super::Sugg;
 698
 699     use rustc_ast::util::parser::AssocOp;
 700     use std::borrow::Cow;
 701
 702     const SUGGESTION: Sugg<'static> = Sugg::NonParen(Cow::Borrowed("function_call()"));
 703
 704     #[test]
 705     fn make_return_transform_sugg_into_a_return_call() {
 706         assert_eq!("return function_call()", SUGGESTION.make_return().to_string());
 707     }
 708
 709     #[test]
 710     fn blockify_transforms_sugg_into_a_block() {
 711         assert_eq!("{ function_call() }", SUGGESTION.blockify().to_string());
 712     }
 713
 714     #[test]
 715     fn binop_maybe_par() {
 716         let sugg = Sugg::BinOp(AssocOp::Add, "(1 + 1)".into());
 717         assert_eq!("(1 + 1)", sugg.maybe_par().to_string());
 718
 719         let sugg = Sugg::BinOp(AssocOp::Add, "(1 + 1) + (1 + 1)".into());
 720         assert_eq!("((1 + 1) + (1 + 1))", sugg.maybe_par().to_string());
 721     }
 722 }