1 //! Contains utility functions to generate suggestions.
2 #![deny(clippy::missing_docs_in_private_items)]
5 snippet, snippet_opt, snippet_with_applicability, snippet_with_context, snippet_with_macro_callsite,
7 use crate::ty::expr_sig;
8 use crate::{get_parent_expr_for_hir, higher};
9 use rustc_ast::util::parser::AssocOp;
10 use rustc_ast::{ast, token};
11 use rustc_ast_pretty::pprust::token_kind_to_string;
12 use rustc_errors::Applicability;
14 use rustc_hir::{Closure, ExprKind, HirId, MutTy, TyKind};
15 use rustc_hir_typeck::expr_use_visitor::{Delegate, ExprUseVisitor, PlaceBase, PlaceWithHirId};
16 use rustc_infer::infer::TyCtxtInferExt;
17 use rustc_lint::{EarlyContext, LateContext, LintContext};
18 use rustc_middle::hir::place::ProjectionKind;
19 use rustc_middle::mir::{FakeReadCause, Mutability};
21 use rustc_span::source_map::{BytePos, CharPos, Pos, Span, SyntaxContext};
23 use std::fmt::{Display, Write as _};
24 use std::ops::{Add, Neg, Not, Sub};
26 /// A helper type to build suggestion correctly handling parentheses.
27 #[derive(Clone, Debug, PartialEq)]
29 /// An expression that never needs parentheses such as `1337` or `[0; 42]`.
30 NonParen(Cow<'a, str>),
31 /// An expression that does not fit in other variants.
32 MaybeParen(Cow<'a, str>),
33 /// A binary operator expression, including `as`-casts and explicit type
35 BinOp(AssocOp, Cow<'a, str>, Cow<'a, str>),
38 /// Literal constant `0`, for convenience.
39 pub const ZERO: Sugg<'static> = Sugg::NonParen(Cow::Borrowed("0"));
40 /// Literal constant `1`, for convenience.
41 pub const ONE: Sugg<'static> = Sugg::NonParen(Cow::Borrowed("1"));
42 /// a constant represents an empty string, for convenience.
43 pub const EMPTY: Sugg<'static> = Sugg::NonParen(Cow::Borrowed(""));
45 impl Display for Sugg<'_> {
46 fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
48 Sugg::NonParen(ref s) | Sugg::MaybeParen(ref s) => s.fmt(f),
49 Sugg::BinOp(op, ref lhs, ref rhs) => binop_to_string(op, lhs, rhs).fmt(f),
54 #[expect(clippy::wrong_self_convention)] // ok, because of the function `as_ty` method
56 /// Prepare a suggestion from an expression.
57 pub fn hir_opt(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option<Self> {
58 let get_snippet = |span| snippet(cx, span, "");
59 snippet_opt(cx, expr.span).map(|_| Self::hir_from_snippet(expr, get_snippet))
62 /// Convenience function around `hir_opt` for suggestions with a default
64 pub fn hir(cx: &LateContext<'_>, expr: &hir::Expr<'_>, default: &'a str) -> Self {
65 Self::hir_opt(cx, expr).unwrap_or(Sugg::NonParen(Cow::Borrowed(default)))
68 /// Same as `hir`, but it adapts the applicability level by following rules:
70 /// - Applicability level `Unspecified` will never be changed.
71 /// - If the span is inside a macro, change the applicability level to `MaybeIncorrect`.
72 /// - If the default value is used and the applicability level is `MachineApplicable`, change it
75 pub fn hir_with_applicability(
79 applicability: &mut Applicability,
81 if *applicability != Applicability::Unspecified && expr.span.from_expansion() {
82 *applicability = Applicability::MaybeIncorrect;
84 Self::hir_opt(cx, expr).unwrap_or_else(|| {
85 if *applicability == Applicability::MachineApplicable {
86 *applicability = Applicability::HasPlaceholders;
88 Sugg::NonParen(Cow::Borrowed(default))
92 /// Same as `hir`, but will use the pre expansion span if the `expr` was in a macro.
93 pub fn hir_with_macro_callsite(cx: &LateContext<'_>, expr: &hir::Expr<'_>, default: &'a str) -> Self {
94 let get_snippet = |span| snippet_with_macro_callsite(cx, span, default);
95 Self::hir_from_snippet(expr, get_snippet)
98 /// Same as `hir`, but first walks the span up to the given context. This will result in the
99 /// macro call, rather then the expansion, if the span is from a child context. If the span is
100 /// not from a child context, it will be used directly instead.
102 /// e.g. Given the expression `&vec![]`, getting a snippet from the span for `vec![]` as a HIR
103 /// node would result in `box []`. If given the context of the address of expression, this
104 /// function will correctly get a snippet of `vec![]`.
105 pub fn hir_with_context(
106 cx: &LateContext<'_>,
107 expr: &hir::Expr<'_>,
110 applicability: &mut Applicability,
112 if expr.span.ctxt() == ctxt {
113 Self::hir_from_snippet(expr, |span| snippet(cx, span, default))
115 let (snip, _) = snippet_with_context(cx, expr.span, ctxt, default, applicability);
120 /// Generate a suggestion for an expression with the given snippet. This is used by the `hir_*`
121 /// function variants of `Sugg`, since these use different snippet functions.
122 fn hir_from_snippet(expr: &hir::Expr<'_>, get_snippet: impl Fn(Span) -> Cow<'a, str>) -> Self {
123 if let Some(range) = higher::Range::hir(expr) {
124 let op = match range.limits {
125 ast::RangeLimits::HalfOpen => AssocOp::DotDot,
126 ast::RangeLimits::Closed => AssocOp::DotDotEq,
128 let start = range.start.map_or("".into(), |expr| get_snippet(expr.span));
129 let end = range.end.map_or("".into(), |expr| get_snippet(expr.span));
131 return Sugg::BinOp(op, start, end);
135 hir::ExprKind::AddrOf(..)
136 | hir::ExprKind::Box(..)
137 | hir::ExprKind::If(..)
138 | hir::ExprKind::Let(..)
139 | hir::ExprKind::Closure { .. }
140 | hir::ExprKind::Unary(..)
141 | hir::ExprKind::Match(..) => Sugg::MaybeParen(get_snippet(expr.span)),
142 hir::ExprKind::Continue(..)
143 | hir::ExprKind::Yield(..)
144 | hir::ExprKind::Array(..)
145 | hir::ExprKind::Block(..)
146 | hir::ExprKind::Break(..)
147 | hir::ExprKind::Call(..)
148 | hir::ExprKind::Field(..)
149 | hir::ExprKind::Index(..)
150 | hir::ExprKind::InlineAsm(..)
151 | hir::ExprKind::ConstBlock(..)
152 | hir::ExprKind::Lit(..)
153 | hir::ExprKind::Loop(..)
154 | hir::ExprKind::MethodCall(..)
155 | hir::ExprKind::Path(..)
156 | hir::ExprKind::Repeat(..)
157 | hir::ExprKind::Ret(..)
158 | hir::ExprKind::Struct(..)
159 | hir::ExprKind::Tup(..)
160 | hir::ExprKind::Err => Sugg::NonParen(get_snippet(expr.span)),
161 hir::ExprKind::DropTemps(inner) => Self::hir_from_snippet(inner, get_snippet),
162 hir::ExprKind::Assign(lhs, rhs, _) => {
163 Sugg::BinOp(AssocOp::Assign, get_snippet(lhs.span), get_snippet(rhs.span))
165 hir::ExprKind::AssignOp(op, lhs, rhs) => {
166 Sugg::BinOp(hirbinop2assignop(op), get_snippet(lhs.span), get_snippet(rhs.span))
168 hir::ExprKind::Binary(op, lhs, rhs) => Sugg::BinOp(
169 AssocOp::from_ast_binop(op.node.into()),
170 get_snippet(lhs.span),
171 get_snippet(rhs.span),
173 hir::ExprKind::Cast(lhs, ty) => Sugg::BinOp(AssocOp::As, get_snippet(lhs.span), get_snippet(ty.span)),
174 hir::ExprKind::Type(lhs, ty) => Sugg::BinOp(AssocOp::Colon, get_snippet(lhs.span), get_snippet(ty.span)),
178 /// Prepare a suggestion from an expression.
180 cx: &EarlyContext<'_>,
184 app: &mut Applicability,
186 use rustc_ast::ast::RangeLimits;
188 #[expect(clippy::match_wildcard_for_single_variants)]
190 _ if expr.span.ctxt() != ctxt => Sugg::NonParen(snippet_with_context(cx, expr.span, ctxt, default, app).0),
191 ast::ExprKind::AddrOf(..)
192 | ast::ExprKind::Box(..)
193 | ast::ExprKind::Closure { .. }
194 | ast::ExprKind::If(..)
195 | ast::ExprKind::Let(..)
196 | ast::ExprKind::Unary(..)
197 | ast::ExprKind::Match(..) => match snippet_with_context(cx, expr.span, ctxt, default, app) {
198 (snip, false) => Sugg::MaybeParen(snip),
199 (snip, true) => Sugg::NonParen(snip),
201 ast::ExprKind::Async(..)
202 | ast::ExprKind::Block(..)
203 | ast::ExprKind::Break(..)
204 | ast::ExprKind::Call(..)
205 | ast::ExprKind::Continue(..)
206 | ast::ExprKind::Yield(..)
207 | ast::ExprKind::Field(..)
208 | ast::ExprKind::ForLoop(..)
209 | ast::ExprKind::Index(..)
210 | ast::ExprKind::InlineAsm(..)
211 | ast::ExprKind::ConstBlock(..)
212 | ast::ExprKind::Lit(..)
213 | ast::ExprKind::IncludedBytes(..)
214 | ast::ExprKind::Loop(..)
215 | ast::ExprKind::MacCall(..)
216 | ast::ExprKind::MethodCall(..)
217 | ast::ExprKind::Paren(..)
218 | ast::ExprKind::Underscore
219 | ast::ExprKind::Path(..)
220 | ast::ExprKind::Repeat(..)
221 | ast::ExprKind::Ret(..)
222 | ast::ExprKind::Yeet(..)
223 | ast::ExprKind::Struct(..)
224 | ast::ExprKind::Try(..)
225 | ast::ExprKind::TryBlock(..)
226 | ast::ExprKind::Tup(..)
227 | ast::ExprKind::Array(..)
228 | ast::ExprKind::While(..)
229 | ast::ExprKind::Await(..)
230 | ast::ExprKind::Err => Sugg::NonParen(snippet_with_context(cx, expr.span, ctxt, default, app).0),
231 ast::ExprKind::Range(ref lhs, ref rhs, RangeLimits::HalfOpen) => Sugg::BinOp(
233 lhs.as_ref().map_or("".into(), |lhs| {
234 snippet_with_context(cx, lhs.span, ctxt, default, app).0
236 rhs.as_ref().map_or("".into(), |rhs| {
237 snippet_with_context(cx, rhs.span, ctxt, default, app).0
240 ast::ExprKind::Range(ref lhs, ref rhs, RangeLimits::Closed) => Sugg::BinOp(
242 lhs.as_ref().map_or("".into(), |lhs| {
243 snippet_with_context(cx, lhs.span, ctxt, default, app).0
245 rhs.as_ref().map_or("".into(), |rhs| {
246 snippet_with_context(cx, rhs.span, ctxt, default, app).0
249 ast::ExprKind::Assign(ref lhs, ref rhs, _) => Sugg::BinOp(
251 snippet_with_context(cx, lhs.span, ctxt, default, app).0,
252 snippet_with_context(cx, rhs.span, ctxt, default, app).0,
254 ast::ExprKind::AssignOp(op, ref lhs, ref rhs) => Sugg::BinOp(
255 astbinop2assignop(op),
256 snippet_with_context(cx, lhs.span, ctxt, default, app).0,
257 snippet_with_context(cx, rhs.span, ctxt, default, app).0,
259 ast::ExprKind::Binary(op, ref lhs, ref rhs) => Sugg::BinOp(
260 AssocOp::from_ast_binop(op.node),
261 snippet_with_context(cx, lhs.span, ctxt, default, app).0,
262 snippet_with_context(cx, rhs.span, ctxt, default, app).0,
264 ast::ExprKind::Cast(ref lhs, ref ty) => Sugg::BinOp(
266 snippet_with_context(cx, lhs.span, ctxt, default, app).0,
267 snippet_with_context(cx, ty.span, ctxt, default, app).0,
269 ast::ExprKind::Type(ref lhs, ref ty) => Sugg::BinOp(
271 snippet_with_context(cx, lhs.span, ctxt, default, app).0,
272 snippet_with_context(cx, ty.span, ctxt, default, app).0,
277 /// Convenience method to create the `<lhs> && <rhs>` suggestion.
278 pub fn and(self, rhs: &Self) -> Sugg<'static> {
279 make_binop(ast::BinOpKind::And, &self, rhs)
282 /// Convenience method to create the `<lhs> & <rhs>` suggestion.
283 pub fn bit_and(self, rhs: &Self) -> Sugg<'static> {
284 make_binop(ast::BinOpKind::BitAnd, &self, rhs)
287 /// Convenience method to create the `<lhs> as <rhs>` suggestion.
288 pub fn as_ty<R: Display>(self, rhs: R) -> Sugg<'static> {
289 make_assoc(AssocOp::As, &self, &Sugg::NonParen(rhs.to_string().into()))
292 /// Convenience method to create the `&<expr>` suggestion.
293 pub fn addr(self) -> Sugg<'static> {
297 /// Convenience method to create the `&mut <expr>` suggestion.
298 pub fn mut_addr(self) -> Sugg<'static> {
299 make_unop("&mut ", self)
302 /// Convenience method to create the `*<expr>` suggestion.
303 pub fn deref(self) -> Sugg<'static> {
307 /// Convenience method to create the `&*<expr>` suggestion. Currently this
308 /// is needed because `sugg.deref().addr()` produces an unnecessary set of
309 /// parentheses around the deref.
310 pub fn addr_deref(self) -> Sugg<'static> {
311 make_unop("&*", self)
314 /// Convenience method to create the `&mut *<expr>` suggestion. Currently
315 /// this is needed because `sugg.deref().mut_addr()` produces an unnecessary
316 /// set of parentheses around the deref.
317 pub fn mut_addr_deref(self) -> Sugg<'static> {
318 make_unop("&mut *", self)
321 /// Convenience method to transform suggestion into a return call
322 pub fn make_return(self) -> Sugg<'static> {
323 Sugg::NonParen(Cow::Owned(format!("return {self}")))
326 /// Convenience method to transform suggestion into a block
327 /// where the suggestion is a trailing expression
328 pub fn blockify(self) -> Sugg<'static> {
329 Sugg::NonParen(Cow::Owned(format!("{{ {self} }}")))
332 /// Convenience method to prefix the expression with the `async` keyword.
333 /// Can be used after `blockify` to create an async block.
334 pub fn asyncify(self) -> Sugg<'static> {
335 Sugg::NonParen(Cow::Owned(format!("async {self}")))
338 /// Convenience method to create the `<lhs>..<rhs>` or `<lhs>...<rhs>`
340 pub fn range(self, end: &Self, limit: ast::RangeLimits) -> Sugg<'static> {
342 ast::RangeLimits::HalfOpen => make_assoc(AssocOp::DotDot, &self, end),
343 ast::RangeLimits::Closed => make_assoc(AssocOp::DotDotEq, &self, end),
347 /// Adds parentheses to any expression that might need them. Suitable to the
348 /// `self` argument of a method call
349 /// (e.g., to build `bar.foo()` or `(1 + 2).foo()`).
351 pub fn maybe_par(self) -> Self {
353 Sugg::NonParen(..) => self,
354 // `(x)` and `(x).y()` both don't need additional parens.
355 Sugg::MaybeParen(sugg) => {
356 if has_enclosing_paren(&sugg) {
357 Sugg::MaybeParen(sugg)
359 Sugg::NonParen(format!("({sugg})").into())
362 Sugg::BinOp(op, lhs, rhs) => {
363 let sugg = binop_to_string(op, &lhs, &rhs);
364 Sugg::NonParen(format!("({sugg})").into())
370 /// Generates a string from the operator and both sides.
371 fn binop_to_string(op: AssocOp, lhs: &str, rhs: &str) -> String {
384 | AssocOp::ShiftRight
390 | AssocOp::GreaterEqual => {
393 op.to_ast_binop().expect("Those are AST ops").to_string()
396 AssocOp::Assign => format!("{lhs} = {rhs}"),
397 AssocOp::AssignOp(op) => {
398 format!("{lhs} {}= {rhs}", token_kind_to_string(&token::BinOp(op)))
400 AssocOp::As => format!("{lhs} as {rhs}"),
401 AssocOp::DotDot => format!("{lhs}..{rhs}"),
402 AssocOp::DotDotEq => format!("{lhs}..={rhs}"),
403 AssocOp::Colon => format!("{lhs}: {rhs}"),
407 /// Return `true` if `sugg` is enclosed in parenthesis.
408 pub fn has_enclosing_paren(sugg: impl AsRef<str>) -> bool {
409 let mut chars = sugg.as_ref().chars();
410 if chars.next() == Some('(') {
412 for c in &mut chars {
422 chars.next().is_none()
428 /// Copied from the rust standard library, and then edited
429 macro_rules! forward_binop_impls_to_ref {
430 (impl $imp:ident, $method:ident for $t:ty, type Output = $o:ty) => {
431 impl $imp<$t> for &$t {
434 fn $method(self, other: $t) -> $o {
435 $imp::$method(self, &other)
439 impl $imp<&$t> for $t {
442 fn $method(self, other: &$t) -> $o {
443 $imp::$method(&self, other)
450 fn $method(self, other: $t) -> $o {
451 $imp::$method(&self, &other)
457 impl Add for &Sugg<'_> {
458 type Output = Sugg<'static>;
459 fn add(self, rhs: &Sugg<'_>) -> Sugg<'static> {
460 make_binop(ast::BinOpKind::Add, self, rhs)
464 impl Sub for &Sugg<'_> {
465 type Output = Sugg<'static>;
466 fn sub(self, rhs: &Sugg<'_>) -> Sugg<'static> {
467 make_binop(ast::BinOpKind::Sub, self, rhs)
471 forward_binop_impls_to_ref!(impl Add, add for Sugg<'_>, type Output = Sugg<'static>);
472 forward_binop_impls_to_ref!(impl Sub, sub for Sugg<'_>, type Output = Sugg<'static>);
474 impl Neg for Sugg<'_> {
475 type Output = Sugg<'static>;
476 fn neg(self) -> Sugg<'static> {
481 impl<'a> Not for Sugg<'a> {
482 type Output = Sugg<'a>;
483 fn not(self) -> Sugg<'a> {
484 use AssocOp::{Equal, Greater, GreaterEqual, Less, LessEqual, NotEqual};
486 if let Sugg::BinOp(op, lhs, rhs) = self {
487 let to_op = match op {
490 Less => GreaterEqual,
491 GreaterEqual => Less,
492 Greater => LessEqual,
493 LessEqual => Greater,
494 _ => return make_unop("!", Sugg::BinOp(op, lhs, rhs)),
496 Sugg::BinOp(to_op, lhs, rhs)
503 /// Helper type to display either `foo` or `(foo)`.
504 struct ParenHelper<T> {
505 /// `true` if parentheses are needed.
507 /// The main thing to display.
511 impl<T> ParenHelper<T> {
512 /// Builds a `ParenHelper`.
513 fn new(paren: bool, wrapped: T) -> Self {
514 Self { paren, wrapped }
518 impl<T: Display> Display for ParenHelper<T> {
519 fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
521 write!(f, "({})", self.wrapped)
528 /// Builds the string for `<op><expr>` adding parenthesis when necessary.
530 /// For convenience, the operator is taken as a string because all unary
531 /// operators have the same
533 pub fn make_unop(op: &str, expr: Sugg<'_>) -> Sugg<'static> {
534 Sugg::MaybeParen(format!("{op}{}", expr.maybe_par()).into())
537 /// Builds the string for `<lhs> <op> <rhs>` adding parenthesis when necessary.
539 /// Precedence of shift operator relative to other arithmetic operation is
540 /// often confusing so
541 /// parenthesis will always be added for a mix of these.
542 pub fn make_assoc(op: AssocOp, lhs: &Sugg<'_>, rhs: &Sugg<'_>) -> Sugg<'static> {
543 /// Returns `true` if the operator is a shift operator `<<` or `>>`.
544 fn is_shift(op: AssocOp) -> bool {
545 matches!(op, AssocOp::ShiftLeft | AssocOp::ShiftRight)
548 /// Returns `true` if the operator is an arithmetic operator
549 /// (i.e., `+`, `-`, `*`, `/`, `%`).
550 fn is_arith(op: AssocOp) -> bool {
553 AssocOp::Add | AssocOp::Subtract | AssocOp::Multiply | AssocOp::Divide | AssocOp::Modulus
557 /// Returns `true` if the operator `op` needs parenthesis with the operator
558 /// `other` in the direction `dir`.
559 fn needs_paren(op: AssocOp, other: AssocOp, dir: Associativity) -> bool {
560 other.precedence() < op.precedence()
561 || (other.precedence() == op.precedence()
562 && ((op != other && associativity(op) != dir)
563 || (op == other && associativity(op) != Associativity::Both)))
564 || is_shift(op) && is_arith(other)
565 || is_shift(other) && is_arith(op)
568 let lhs_paren = if let Sugg::BinOp(lop, _, _) = *lhs {
569 needs_paren(op, lop, Associativity::Left)
574 let rhs_paren = if let Sugg::BinOp(rop, _, _) = *rhs {
575 needs_paren(op, rop, Associativity::Right)
580 let lhs = ParenHelper::new(lhs_paren, lhs).to_string();
581 let rhs = ParenHelper::new(rhs_paren, rhs).to_string();
582 Sugg::BinOp(op, lhs.into(), rhs.into())
585 /// Convenience wrapper around `make_assoc` and `AssocOp::from_ast_binop`.
586 pub fn make_binop(op: ast::BinOpKind, lhs: &Sugg<'_>, rhs: &Sugg<'_>) -> Sugg<'static> {
587 make_assoc(AssocOp::from_ast_binop(op), lhs, rhs)
590 #[derive(PartialEq, Eq, Clone, Copy)]
591 /// Operator associativity.
593 /// The operator is both left-associative and right-associative.
595 /// The operator is left-associative.
597 /// The operator is not associative.
599 /// The operator is right-associative.
603 /// Returns the associativity/fixity of an operator. The difference with
604 /// `AssocOp::fixity` is that an operator can be both left and right associative
605 /// (such as `+`: `a + b + c == (a + b) + c == a + (b + c)`.
607 /// Chained `as` and explicit `:` type coercion never need inner parenthesis so
608 /// they are considered
611 fn associativity(op: AssocOp) -> Associativity {
612 use rustc_ast::util::parser::AssocOp::{
613 Add, As, Assign, AssignOp, BitAnd, BitOr, BitXor, Colon, Divide, DotDot, DotDotEq, Equal, Greater,
614 GreaterEqual, LAnd, LOr, Less, LessEqual, Modulus, Multiply, NotEqual, ShiftLeft, ShiftRight, Subtract,
618 Assign | AssignOp(_) => Associativity::Right,
619 Add | BitAnd | BitOr | BitXor | LAnd | LOr | Multiply | As | Colon => Associativity::Both,
620 Divide | Equal | Greater | GreaterEqual | Less | LessEqual | Modulus | NotEqual | ShiftLeft | ShiftRight
621 | Subtract => Associativity::Left,
622 DotDot | DotDotEq => Associativity::None,
626 /// Converts a `hir::BinOp` to the corresponding assigning binary operator.
627 fn hirbinop2assignop(op: hir::BinOp) -> AssocOp {
628 use rustc_ast::token::BinOpToken::{And, Caret, Minus, Or, Percent, Plus, Shl, Shr, Slash, Star};
630 AssocOp::AssignOp(match op.node {
631 hir::BinOpKind::Add => Plus,
632 hir::BinOpKind::BitAnd => And,
633 hir::BinOpKind::BitOr => Or,
634 hir::BinOpKind::BitXor => Caret,
635 hir::BinOpKind::Div => Slash,
636 hir::BinOpKind::Mul => Star,
637 hir::BinOpKind::Rem => Percent,
638 hir::BinOpKind::Shl => Shl,
639 hir::BinOpKind::Shr => Shr,
640 hir::BinOpKind::Sub => Minus,
649 | hir::BinOpKind::Or => panic!("This operator does not exist"),
653 /// Converts an `ast::BinOp` to the corresponding assigning binary operator.
654 fn astbinop2assignop(op: ast::BinOp) -> AssocOp {
655 use rustc_ast::ast::BinOpKind::{
656 Add, And, BitAnd, BitOr, BitXor, Div, Eq, Ge, Gt, Le, Lt, Mul, Ne, Or, Rem, Shl, Shr, Sub,
658 use rustc_ast::token::BinOpToken;
660 AssocOp::AssignOp(match op.node {
661 Add => BinOpToken::Plus,
662 BitAnd => BinOpToken::And,
663 BitOr => BinOpToken::Or,
664 BitXor => BinOpToken::Caret,
665 Div => BinOpToken::Slash,
666 Mul => BinOpToken::Star,
667 Rem => BinOpToken::Percent,
668 Shl => BinOpToken::Shl,
669 Shr => BinOpToken::Shr,
670 Sub => BinOpToken::Minus,
671 And | Eq | Ge | Gt | Le | Lt | Ne | Or => panic!("This operator does not exist"),
675 /// Returns the indentation before `span` if there are nothing but `[ \t]`
676 /// before it on its line.
677 fn indentation<T: LintContext>(cx: &T, span: Span) -> Option<String> {
678 let lo = cx.sess().source_map().lookup_char_pos(span.lo());
680 .get_line(lo.line - 1 /* line numbers in `Loc` are 1-based */)
682 if let Some((pos, _)) = line.char_indices().find(|&(_, c)| c != ' ' && c != '\t') {
683 // We can mix char and byte positions here because we only consider `[ \t]`.
684 if lo.col == CharPos(pos) {
685 Some(line[..pos].into())
695 /// Convenience extension trait for `Diagnostic`.
696 pub trait DiagnosticExt<T: LintContext> {
697 /// Suggests to add an attribute to an item.
699 /// Correctly handles indentation of the attribute and item.
704 /// diag.suggest_item_with_attr(cx, item, "#[derive(Default)]");
706 fn suggest_item_with_attr<D: Display + ?Sized>(
712 applicability: Applicability,
715 /// Suggest to add an item before another.
717 /// The item should not be indented (except for inner indentation).
722 /// diag.suggest_prepend_item(cx, item,
727 fn suggest_prepend_item(&mut self, cx: &T, item: Span, msg: &str, new_item: &str, applicability: Applicability);
729 /// Suggest to completely remove an item.
731 /// This will remove an item and all following whitespace until the next non-whitespace
732 /// character. This should work correctly if item is on the same indentation level as the
738 /// diag.suggest_remove_item(cx, item, "remove this")
740 fn suggest_remove_item(&mut self, cx: &T, item: Span, msg: &str, applicability: Applicability);
743 impl<T: LintContext> DiagnosticExt<T> for rustc_errors::Diagnostic {
744 fn suggest_item_with_attr<D: Display + ?Sized>(
750 applicability: Applicability,
752 if let Some(indent) = indentation(cx, item) {
753 let span = item.with_hi(item.lo());
755 self.span_suggestion(span, msg, format!("{attr}\n{indent}"), applicability);
759 fn suggest_prepend_item(&mut self, cx: &T, item: Span, msg: &str, new_item: &str, applicability: Applicability) {
760 if let Some(indent) = indentation(cx, item) {
761 let span = item.with_hi(item.lo());
763 let mut first = true;
764 let new_item = new_item
771 format!("{indent}{l}\n")
774 .collect::<String>();
776 self.span_suggestion(span, msg, format!("{new_item}\n{indent}"), applicability);
780 fn suggest_remove_item(&mut self, cx: &T, item: Span, msg: &str, applicability: Applicability) {
781 let mut remove_span = item;
782 let fmpos = cx.sess().source_map().lookup_byte_offset(remove_span.hi());
784 if let Some(ref src) = fmpos.sf.src {
785 let non_whitespace_offset = src[fmpos.pos.to_usize()..].find(|c| c != ' ' && c != '\t' && c != '\n');
787 if let Some(non_whitespace_offset) = non_whitespace_offset {
788 remove_span = remove_span
789 .with_hi(remove_span.hi() + BytePos(non_whitespace_offset.try_into().expect("offset too large")));
793 self.span_suggestion(remove_span, msg, "", applicability);
797 /// Suggestion results for handling closure
798 /// args dereferencing and borrowing
799 pub struct DerefClosure {
800 /// confidence on the built suggestion
801 pub applicability: Applicability,
802 /// gradually built suggestion
803 pub suggestion: String,
806 /// Build suggestion gradually by handling closure arg specific usages,
807 /// such as explicit deref and borrowing cases.
808 /// Returns `None` if no such use cases have been triggered in closure body
810 /// note: this only works on single line immutable closures with exactly one input parameter.
811 pub fn deref_closure_args(cx: &LateContext<'_>, closure: &hir::Expr<'_>) -> Option<DerefClosure> {
812 if let hir::ExprKind::Closure(&Closure { fn_decl, body, .. }) = closure.kind {
813 let closure_body = cx.tcx.hir().body(body);
814 // is closure arg a type annotated double reference (i.e.: `|x: &&i32| ...`)
815 // a type annotation is present if param `kind` is different from `TyKind::Infer`
816 let closure_arg_is_type_annotated_double_ref = if let TyKind::Rptr(_, MutTy { ty, .. }) = fn_decl.inputs[0].kind
818 matches!(ty.kind, TyKind::Rptr(_, MutTy { .. }))
823 let mut visitor = DerefDelegate {
825 closure_span: closure.span,
826 closure_arg_is_type_annotated_double_ref,
827 next_pos: closure.span.lo(),
828 suggestion_start: String::new(),
829 applicability: Applicability::MachineApplicable,
832 let fn_def_id = cx.tcx.hir().local_def_id(closure.hir_id);
833 let infcx = cx.tcx.infer_ctxt().build();
834 ExprUseVisitor::new(&mut visitor, &infcx, fn_def_id, cx.param_env, cx.typeck_results())
835 .consume_body(closure_body);
837 if !visitor.suggestion_start.is_empty() {
838 return Some(DerefClosure {
839 applicability: visitor.applicability,
840 suggestion: visitor.finish(),
847 /// Visitor struct used for tracking down
848 /// dereferencing and borrowing of closure's args
849 struct DerefDelegate<'a, 'tcx> {
850 /// The late context of the lint
851 cx: &'a LateContext<'tcx>,
852 /// The span of the input closure to adapt
854 /// Indicates if the arg of the closure is a type annotated double reference
855 closure_arg_is_type_annotated_double_ref: bool,
856 /// last position of the span to gradually build the suggestion
858 /// starting part of the gradually built suggestion
859 suggestion_start: String,
860 /// confidence on the built suggestion
861 applicability: Applicability,
864 impl<'tcx> DerefDelegate<'_, 'tcx> {
865 /// build final suggestion:
866 /// - create the ending part of suggestion
867 /// - concatenate starting and ending parts
868 /// - potentially remove needless borrowing
869 pub fn finish(&mut self) -> String {
870 let end_span = Span::new(self.next_pos, self.closure_span.hi(), self.closure_span.ctxt(), None);
871 let end_snip = snippet_with_applicability(self.cx, end_span, "..", &mut self.applicability);
872 let sugg = format!("{}{end_snip}", self.suggestion_start);
873 if self.closure_arg_is_type_annotated_double_ref {
874 sugg.replacen('&', "", 1)
880 /// indicates whether the function from `parent_expr` takes its args by double reference
881 fn func_takes_arg_by_double_ref(&self, parent_expr: &'tcx hir::Expr<'_>, cmt_hir_id: HirId) -> bool {
882 let ty = match parent_expr.kind {
883 ExprKind::MethodCall(_, receiver, call_args, _) => {
884 if let Some(sig) = self
887 .type_dependent_def_id(parent_expr.hir_id)
888 .map(|did| self.cx.tcx.fn_sig(did).skip_binder())
890 std::iter::once(receiver)
891 .chain(call_args.iter())
892 .position(|arg| arg.hir_id == cmt_hir_id)
893 .map(|i| sig.inputs()[i])
898 ExprKind::Call(func, call_args) => {
899 if let Some(sig) = expr_sig(self.cx, func) {
902 .position(|arg| arg.hir_id == cmt_hir_id)
903 .and_then(|i| sig.input(i))
904 .map(ty::Binder::skip_binder)
912 ty.map_or(false, |ty| matches!(ty.kind(), ty::Ref(_, inner, _) if inner.is_ref()))
916 impl<'tcx> Delegate<'tcx> for DerefDelegate<'_, 'tcx> {
917 fn consume(&mut self, _: &PlaceWithHirId<'tcx>, _: HirId) {}
919 fn borrow(&mut self, cmt: &PlaceWithHirId<'tcx>, _: HirId, _: ty::BorrowKind) {
920 if let PlaceBase::Local(id) = cmt.place.base {
921 let map = self.cx.tcx.hir();
922 let span = map.span(cmt.hir_id);
923 let start_span = Span::new(self.next_pos, span.lo(), span.ctxt(), None);
924 let mut start_snip = snippet_with_applicability(self.cx, start_span, "..", &mut self.applicability);
926 // identifier referring to the variable currently triggered (i.e.: `fp`)
927 let ident_str = map.name(id).to_string();
928 // full identifier that includes projection (i.e.: `fp.field`)
929 let ident_str_with_proj = snippet(self.cx, span, "..").to_string();
931 if cmt.place.projections.is_empty() {
932 // handle item without any projection, that needs an explicit borrowing
933 // i.e.: suggest `&x` instead of `x`
934 let _ = write!(self.suggestion_start, "{start_snip}&{ident_str}");
936 // cases where a parent `Call` or `MethodCall` is using the item
937 // i.e.: suggest `.contains(&x)` for `.find(|x| [1, 2, 3].contains(x)).is_none()`
939 // Note about method calls:
940 // - compiler automatically dereference references if the target type is a reference (works also for
942 // - `self` arguments in the case of `x.is_something()` are also automatically (de)referenced, and
943 // no projection should be suggested
944 if let Some(parent_expr) = get_parent_expr_for_hir(self.cx, cmt.hir_id) {
945 match &parent_expr.kind {
946 // given expression is the self argument and will be handled completely by the compiler
947 // i.e.: `|x| x.is_something()`
948 ExprKind::MethodCall(_, self_expr, ..) if self_expr.hir_id == cmt.hir_id => {
949 let _ = write!(self.suggestion_start, "{start_snip}{ident_str_with_proj}");
950 self.next_pos = span.hi();
953 // item is used in a call
954 // i.e.: `Call`: `|x| please(x)` or `MethodCall`: `|x| [1, 2, 3].contains(x)`
955 ExprKind::Call(_, [call_args @ ..]) | ExprKind::MethodCall(_, _, [call_args @ ..], _) => {
956 let expr = self.cx.tcx.hir().expect_expr(cmt.hir_id);
957 let arg_ty_kind = self.cx.typeck_results().expr_ty(expr).kind();
959 if matches!(arg_ty_kind, ty::Ref(_, _, Mutability::Not)) {
960 // suggest ampersand if call function is taking args by double reference
961 let takes_arg_by_double_ref =
962 self.func_takes_arg_by_double_ref(parent_expr, cmt.hir_id);
964 // compiler will automatically dereference field or index projection, so no need
965 // to suggest ampersand, but full identifier that includes projection is required
966 let has_field_or_index_projection =
967 cmt.place.projections.iter().any(|proj| {
968 matches!(proj.kind, ProjectionKind::Field(..) | ProjectionKind::Index)
971 // no need to bind again if the function doesn't take arg by double ref
972 // and if the item is already a double ref
973 let ident_sugg = if !call_args.is_empty()
974 && !takes_arg_by_double_ref
975 && (self.closure_arg_is_type_annotated_double_ref || has_field_or_index_projection)
977 let ident = if has_field_or_index_projection {
982 format!("{start_snip}{ident}")
984 format!("{start_snip}&{ident_str}")
986 self.suggestion_start.push_str(&ident_sugg);
987 self.next_pos = span.hi();
991 self.applicability = Applicability::Unspecified;
997 let mut replacement_str = ident_str;
998 let mut projections_handled = false;
999 cmt.place.projections.iter().enumerate().for_each(|(i, proj)| {
1001 // Field projection like `|v| v.foo`
1002 // no adjustment needed here, as field projections are handled by the compiler
1003 ProjectionKind::Field(..) => match cmt.place.ty_before_projection(i).kind() {
1004 ty::Adt(..) | ty::Tuple(_) => {
1005 replacement_str = ident_str_with_proj.clone();
1006 projections_handled = true;
1010 // Index projection like `|x| foo[x]`
1011 // the index is dropped so we can't get it to build the suggestion,
1012 // so the span is set-up again to get more code, using `span.hi()` (i.e.: `foo[x]`)
1013 // instead of `span.lo()` (i.e.: `foo`)
1014 ProjectionKind::Index => {
1015 let start_span = Span::new(self.next_pos, span.hi(), span.ctxt(), None);
1016 start_snip = snippet_with_applicability(self.cx, start_span, "..", &mut self.applicability);
1017 replacement_str.clear();
1018 projections_handled = true;
1020 // note: unable to trigger `Subslice` kind in tests
1021 ProjectionKind::Subslice => (),
1022 ProjectionKind::Deref => {
1023 // Explicit derefs are typically handled later on, but
1024 // some items do not need explicit deref, such as array accesses,
1025 // so we mark them as already processed
1026 // i.e.: don't suggest `*sub[1..4].len()` for `|sub| sub[1..4].len() == 3`
1027 if let ty::Ref(_, inner, _) = cmt.place.ty_before_projection(i).kind() {
1028 if matches!(inner.kind(), ty::Ref(_, innermost, _) if innermost.is_array()) {
1029 projections_handled = true;
1036 // handle `ProjectionKind::Deref` by removing one explicit deref
1037 // if no special case was detected (i.e.: suggest `*x` instead of `**x`)
1038 if !projections_handled {
1039 let last_deref = cmt
1043 .rposition(|proj| proj.kind == ProjectionKind::Deref);
1045 if let Some(pos) = last_deref {
1046 let mut projections = cmt.place.projections.clone();
1047 projections.truncate(pos);
1049 for item in projections {
1050 if item.kind == ProjectionKind::Deref {
1051 replacement_str = format!("*{replacement_str}");
1057 let _ = write!(self.suggestion_start, "{start_snip}{replacement_str}");
1059 self.next_pos = span.hi();
1063 fn mutate(&mut self, _: &PlaceWithHirId<'tcx>, _: HirId) {}
1065 fn fake_read(&mut self, _: &PlaceWithHirId<'tcx>, _: FakeReadCause, _: HirId) {}
1072 use rustc_ast::util::parser::AssocOp;
1073 use std::borrow::Cow;
1075 const SUGGESTION: Sugg<'static> = Sugg::NonParen(Cow::Borrowed("function_call()"));
1078 fn make_return_transform_sugg_into_a_return_call() {
1079 assert_eq!("return function_call()", SUGGESTION.make_return().to_string());
1083 fn blockify_transforms_sugg_into_a_block() {
1084 assert_eq!("{ function_call() }", SUGGESTION.blockify().to_string());
1088 fn binop_maybe_par() {
1089 let sugg = Sugg::BinOp(AssocOp::Add, "1".into(), "1".into());
1090 assert_eq!("(1 + 1)", sugg.maybe_par().to_string());
1092 let sugg = Sugg::BinOp(AssocOp::Add, "(1 + 1)".into(), "(1 + 1)".into());
1093 assert_eq!("((1 + 1) + (1 + 1))", sugg.maybe_par().to_string());
1097 use AssocOp::{Add, Equal, Greater, GreaterEqual, LAnd, LOr, Less, LessEqual, NotEqual};
1099 fn test_not(op: AssocOp, correct: &str) {
1100 let sugg = Sugg::BinOp(op, "x".into(), "y".into());
1101 assert_eq!((!sugg).to_string(), correct);
1104 // Invert the comparison operator.
1105 test_not(Equal, "x != y");
1106 test_not(NotEqual, "x == y");
1107 test_not(Less, "x >= y");
1108 test_not(LessEqual, "x > y");
1109 test_not(Greater, "x <= y");
1110 test_not(GreaterEqual, "x < y");
1112 // Other operators are inverted like !(..).
1113 test_not(Add, "!(x + y)");
1114 test_not(LAnd, "!(x && y)");
1115 test_not(LOr, "!(x || y)");