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.
179 pub fn ast(cx: &EarlyContext<'_>, expr: &ast::Expr, default: &'a str) -> Self {
180 use rustc_ast::ast::RangeLimits;
182 let snippet_without_expansion = |cx, span: Span, default| {
183 if span.from_expansion() {
184 snippet_with_macro_callsite(cx, span, default)
186 snippet(cx, span, default)
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(..) => Sugg::MaybeParen(snippet_without_expansion(cx, expr.span, default)),
198 ast::ExprKind::Async(..)
199 | ast::ExprKind::Block(..)
200 | ast::ExprKind::Break(..)
201 | ast::ExprKind::Call(..)
202 | ast::ExprKind::Continue(..)
203 | ast::ExprKind::Yield(..)
204 | ast::ExprKind::Field(..)
205 | ast::ExprKind::ForLoop(..)
206 | ast::ExprKind::Index(..)
207 | ast::ExprKind::InlineAsm(..)
208 | ast::ExprKind::ConstBlock(..)
209 | ast::ExprKind::Lit(..)
210 | ast::ExprKind::IncludedBytes(..)
211 | ast::ExprKind::Loop(..)
212 | ast::ExprKind::MacCall(..)
213 | ast::ExprKind::MethodCall(..)
214 | ast::ExprKind::Paren(..)
215 | ast::ExprKind::Underscore
216 | ast::ExprKind::Path(..)
217 | ast::ExprKind::Repeat(..)
218 | ast::ExprKind::Ret(..)
219 | ast::ExprKind::Yeet(..)
220 | ast::ExprKind::Struct(..)
221 | ast::ExprKind::Try(..)
222 | ast::ExprKind::TryBlock(..)
223 | ast::ExprKind::Tup(..)
224 | ast::ExprKind::Array(..)
225 | ast::ExprKind::While(..)
226 | ast::ExprKind::Await(..)
227 | ast::ExprKind::Err => Sugg::NonParen(snippet_without_expansion(cx, expr.span, default)),
228 ast::ExprKind::Range(ref lhs, ref rhs, RangeLimits::HalfOpen) => Sugg::BinOp(
231 .map_or("".into(), |lhs| snippet_without_expansion(cx, lhs.span, default)),
233 .map_or("".into(), |rhs| snippet_without_expansion(cx, rhs.span, default)),
235 ast::ExprKind::Range(ref lhs, ref rhs, RangeLimits::Closed) => Sugg::BinOp(
238 .map_or("".into(), |lhs| snippet_without_expansion(cx, lhs.span, default)),
240 .map_or("".into(), |rhs| snippet_without_expansion(cx, rhs.span, default)),
242 ast::ExprKind::Assign(ref lhs, ref rhs, _) => Sugg::BinOp(
244 snippet_without_expansion(cx, lhs.span, default),
245 snippet_without_expansion(cx, rhs.span, default),
247 ast::ExprKind::AssignOp(op, ref lhs, ref rhs) => Sugg::BinOp(
248 astbinop2assignop(op),
249 snippet_without_expansion(cx, lhs.span, default),
250 snippet_without_expansion(cx, rhs.span, default),
252 ast::ExprKind::Binary(op, ref lhs, ref rhs) => Sugg::BinOp(
253 AssocOp::from_ast_binop(op.node),
254 snippet_without_expansion(cx, lhs.span, default),
255 snippet_without_expansion(cx, rhs.span, default),
257 ast::ExprKind::Cast(ref lhs, ref ty) => Sugg::BinOp(
259 snippet_without_expansion(cx, lhs.span, default),
260 snippet_without_expansion(cx, ty.span, default),
262 ast::ExprKind::Type(ref lhs, ref ty) => Sugg::BinOp(
264 snippet_without_expansion(cx, lhs.span, default),
265 snippet_without_expansion(cx, ty.span, default),
270 /// Convenience method to create the `<lhs> && <rhs>` suggestion.
271 pub fn and(self, rhs: &Self) -> Sugg<'static> {
272 make_binop(ast::BinOpKind::And, &self, rhs)
275 /// Convenience method to create the `<lhs> & <rhs>` suggestion.
276 pub fn bit_and(self, rhs: &Self) -> Sugg<'static> {
277 make_binop(ast::BinOpKind::BitAnd, &self, rhs)
280 /// Convenience method to create the `<lhs> as <rhs>` suggestion.
281 pub fn as_ty<R: Display>(self, rhs: R) -> Sugg<'static> {
282 make_assoc(AssocOp::As, &self, &Sugg::NonParen(rhs.to_string().into()))
285 /// Convenience method to create the `&<expr>` suggestion.
286 pub fn addr(self) -> Sugg<'static> {
290 /// Convenience method to create the `&mut <expr>` suggestion.
291 pub fn mut_addr(self) -> Sugg<'static> {
292 make_unop("&mut ", self)
295 /// Convenience method to create the `*<expr>` suggestion.
296 pub fn deref(self) -> Sugg<'static> {
300 /// Convenience method to create the `&*<expr>` suggestion. Currently this
301 /// is needed because `sugg.deref().addr()` produces an unnecessary set of
302 /// parentheses around the deref.
303 pub fn addr_deref(self) -> Sugg<'static> {
304 make_unop("&*", self)
307 /// Convenience method to create the `&mut *<expr>` suggestion. Currently
308 /// this is needed because `sugg.deref().mut_addr()` produces an unnecessary
309 /// set of parentheses around the deref.
310 pub fn mut_addr_deref(self) -> Sugg<'static> {
311 make_unop("&mut *", self)
314 /// Convenience method to transform suggestion into a return call
315 pub fn make_return(self) -> Sugg<'static> {
316 Sugg::NonParen(Cow::Owned(format!("return {self}")))
319 /// Convenience method to transform suggestion into a block
320 /// where the suggestion is a trailing expression
321 pub fn blockify(self) -> Sugg<'static> {
322 Sugg::NonParen(Cow::Owned(format!("{{ {self} }}")))
325 /// Convenience method to prefix the expression with the `async` keyword.
326 /// Can be used after `blockify` to create an async block.
327 pub fn asyncify(self) -> Sugg<'static> {
328 Sugg::NonParen(Cow::Owned(format!("async {self}")))
331 /// Convenience method to create the `<lhs>..<rhs>` or `<lhs>...<rhs>`
333 pub fn range(self, end: &Self, limit: ast::RangeLimits) -> Sugg<'static> {
335 ast::RangeLimits::HalfOpen => make_assoc(AssocOp::DotDot, &self, end),
336 ast::RangeLimits::Closed => make_assoc(AssocOp::DotDotEq, &self, end),
340 /// Adds parentheses to any expression that might need them. Suitable to the
341 /// `self` argument of a method call
342 /// (e.g., to build `bar.foo()` or `(1 + 2).foo()`).
344 pub fn maybe_par(self) -> Self {
346 Sugg::NonParen(..) => self,
347 // `(x)` and `(x).y()` both don't need additional parens.
348 Sugg::MaybeParen(sugg) => {
349 if has_enclosing_paren(&sugg) {
350 Sugg::MaybeParen(sugg)
352 Sugg::NonParen(format!("({sugg})").into())
355 Sugg::BinOp(op, lhs, rhs) => {
356 let sugg = binop_to_string(op, &lhs, &rhs);
357 Sugg::NonParen(format!("({sugg})").into())
363 /// Generates a string from the operator and both sides.
364 fn binop_to_string(op: AssocOp, lhs: &str, rhs: &str) -> String {
377 | AssocOp::ShiftRight
383 | AssocOp::GreaterEqual => {
386 op.to_ast_binop().expect("Those are AST ops").to_string()
389 AssocOp::Assign => format!("{lhs} = {rhs}"),
390 AssocOp::AssignOp(op) => {
391 format!("{lhs} {}= {rhs}", token_kind_to_string(&token::BinOp(op)))
393 AssocOp::As => format!("{lhs} as {rhs}"),
394 AssocOp::DotDot => format!("{lhs}..{rhs}"),
395 AssocOp::DotDotEq => format!("{lhs}..={rhs}"),
396 AssocOp::Colon => format!("{lhs}: {rhs}"),
400 /// Return `true` if `sugg` is enclosed in parenthesis.
401 pub fn has_enclosing_paren(sugg: impl AsRef<str>) -> bool {
402 let mut chars = sugg.as_ref().chars();
403 if chars.next() == Some('(') {
405 for c in &mut chars {
415 chars.next().is_none()
421 /// Copied from the rust standard library, and then edited
422 macro_rules! forward_binop_impls_to_ref {
423 (impl $imp:ident, $method:ident for $t:ty, type Output = $o:ty) => {
424 impl $imp<$t> for &$t {
427 fn $method(self, other: $t) -> $o {
428 $imp::$method(self, &other)
432 impl $imp<&$t> for $t {
435 fn $method(self, other: &$t) -> $o {
436 $imp::$method(&self, other)
443 fn $method(self, other: $t) -> $o {
444 $imp::$method(&self, &other)
450 impl Add for &Sugg<'_> {
451 type Output = Sugg<'static>;
452 fn add(self, rhs: &Sugg<'_>) -> Sugg<'static> {
453 make_binop(ast::BinOpKind::Add, self, rhs)
457 impl Sub for &Sugg<'_> {
458 type Output = Sugg<'static>;
459 fn sub(self, rhs: &Sugg<'_>) -> Sugg<'static> {
460 make_binop(ast::BinOpKind::Sub, self, rhs)
464 forward_binop_impls_to_ref!(impl Add, add for Sugg<'_>, type Output = Sugg<'static>);
465 forward_binop_impls_to_ref!(impl Sub, sub for Sugg<'_>, type Output = Sugg<'static>);
467 impl Neg for Sugg<'_> {
468 type Output = Sugg<'static>;
469 fn neg(self) -> Sugg<'static> {
474 impl<'a> Not for Sugg<'a> {
475 type Output = Sugg<'a>;
476 fn not(self) -> Sugg<'a> {
477 use AssocOp::{Equal, Greater, GreaterEqual, Less, LessEqual, NotEqual};
479 if let Sugg::BinOp(op, lhs, rhs) = self {
480 let to_op = match op {
483 Less => GreaterEqual,
484 GreaterEqual => Less,
485 Greater => LessEqual,
486 LessEqual => Greater,
487 _ => return make_unop("!", Sugg::BinOp(op, lhs, rhs)),
489 Sugg::BinOp(to_op, lhs, rhs)
496 /// Helper type to display either `foo` or `(foo)`.
497 struct ParenHelper<T> {
498 /// `true` if parentheses are needed.
500 /// The main thing to display.
504 impl<T> ParenHelper<T> {
505 /// Builds a `ParenHelper`.
506 fn new(paren: bool, wrapped: T) -> Self {
507 Self { paren, wrapped }
511 impl<T: Display> Display for ParenHelper<T> {
512 fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
514 write!(f, "({})", self.wrapped)
521 /// Builds the string for `<op><expr>` adding parenthesis when necessary.
523 /// For convenience, the operator is taken as a string because all unary
524 /// operators have the same
526 pub fn make_unop(op: &str, expr: Sugg<'_>) -> Sugg<'static> {
527 Sugg::MaybeParen(format!("{op}{}", expr.maybe_par()).into())
530 /// Builds the string for `<lhs> <op> <rhs>` adding parenthesis when necessary.
532 /// Precedence of shift operator relative to other arithmetic operation is
533 /// often confusing so
534 /// parenthesis will always be added for a mix of these.
535 pub fn make_assoc(op: AssocOp, lhs: &Sugg<'_>, rhs: &Sugg<'_>) -> Sugg<'static> {
536 /// Returns `true` if the operator is a shift operator `<<` or `>>`.
537 fn is_shift(op: AssocOp) -> bool {
538 matches!(op, AssocOp::ShiftLeft | AssocOp::ShiftRight)
541 /// Returns `true` if the operator is an arithmetic operator
542 /// (i.e., `+`, `-`, `*`, `/`, `%`).
543 fn is_arith(op: AssocOp) -> bool {
546 AssocOp::Add | AssocOp::Subtract | AssocOp::Multiply | AssocOp::Divide | AssocOp::Modulus
550 /// Returns `true` if the operator `op` needs parenthesis with the operator
551 /// `other` in the direction `dir`.
552 fn needs_paren(op: AssocOp, other: AssocOp, dir: Associativity) -> bool {
553 other.precedence() < op.precedence()
554 || (other.precedence() == op.precedence()
555 && ((op != other && associativity(op) != dir)
556 || (op == other && associativity(op) != Associativity::Both)))
557 || is_shift(op) && is_arith(other)
558 || is_shift(other) && is_arith(op)
561 let lhs_paren = if let Sugg::BinOp(lop, _, _) = *lhs {
562 needs_paren(op, lop, Associativity::Left)
567 let rhs_paren = if let Sugg::BinOp(rop, _, _) = *rhs {
568 needs_paren(op, rop, Associativity::Right)
573 let lhs = ParenHelper::new(lhs_paren, lhs).to_string();
574 let rhs = ParenHelper::new(rhs_paren, rhs).to_string();
575 Sugg::BinOp(op, lhs.into(), rhs.into())
578 /// Convenience wrapper around `make_assoc` and `AssocOp::from_ast_binop`.
579 pub fn make_binop(op: ast::BinOpKind, lhs: &Sugg<'_>, rhs: &Sugg<'_>) -> Sugg<'static> {
580 make_assoc(AssocOp::from_ast_binop(op), lhs, rhs)
583 #[derive(PartialEq, Eq, Clone, Copy)]
584 /// Operator associativity.
586 /// The operator is both left-associative and right-associative.
588 /// The operator is left-associative.
590 /// The operator is not associative.
592 /// The operator is right-associative.
596 /// Returns the associativity/fixity of an operator. The difference with
597 /// `AssocOp::fixity` is that an operator can be both left and right associative
598 /// (such as `+`: `a + b + c == (a + b) + c == a + (b + c)`.
600 /// Chained `as` and explicit `:` type coercion never need inner parenthesis so
601 /// they are considered
604 fn associativity(op: AssocOp) -> Associativity {
605 use rustc_ast::util::parser::AssocOp::{
606 Add, As, Assign, AssignOp, BitAnd, BitOr, BitXor, Colon, Divide, DotDot, DotDotEq, Equal, Greater,
607 GreaterEqual, LAnd, LOr, Less, LessEqual, Modulus, Multiply, NotEqual, ShiftLeft, ShiftRight, Subtract,
611 Assign | AssignOp(_) => Associativity::Right,
612 Add | BitAnd | BitOr | BitXor | LAnd | LOr | Multiply | As | Colon => Associativity::Both,
613 Divide | Equal | Greater | GreaterEqual | Less | LessEqual | Modulus | NotEqual | ShiftLeft | ShiftRight
614 | Subtract => Associativity::Left,
615 DotDot | DotDotEq => Associativity::None,
619 /// Converts a `hir::BinOp` to the corresponding assigning binary operator.
620 fn hirbinop2assignop(op: hir::BinOp) -> AssocOp {
621 use rustc_ast::token::BinOpToken::{And, Caret, Minus, Or, Percent, Plus, Shl, Shr, Slash, Star};
623 AssocOp::AssignOp(match op.node {
624 hir::BinOpKind::Add => Plus,
625 hir::BinOpKind::BitAnd => And,
626 hir::BinOpKind::BitOr => Or,
627 hir::BinOpKind::BitXor => Caret,
628 hir::BinOpKind::Div => Slash,
629 hir::BinOpKind::Mul => Star,
630 hir::BinOpKind::Rem => Percent,
631 hir::BinOpKind::Shl => Shl,
632 hir::BinOpKind::Shr => Shr,
633 hir::BinOpKind::Sub => Minus,
642 | hir::BinOpKind::Or => panic!("This operator does not exist"),
646 /// Converts an `ast::BinOp` to the corresponding assigning binary operator.
647 fn astbinop2assignop(op: ast::BinOp) -> AssocOp {
648 use rustc_ast::ast::BinOpKind::{
649 Add, And, BitAnd, BitOr, BitXor, Div, Eq, Ge, Gt, Le, Lt, Mul, Ne, Or, Rem, Shl, Shr, Sub,
651 use rustc_ast::token::BinOpToken;
653 AssocOp::AssignOp(match op.node {
654 Add => BinOpToken::Plus,
655 BitAnd => BinOpToken::And,
656 BitOr => BinOpToken::Or,
657 BitXor => BinOpToken::Caret,
658 Div => BinOpToken::Slash,
659 Mul => BinOpToken::Star,
660 Rem => BinOpToken::Percent,
661 Shl => BinOpToken::Shl,
662 Shr => BinOpToken::Shr,
663 Sub => BinOpToken::Minus,
664 And | Eq | Ge | Gt | Le | Lt | Ne | Or => panic!("This operator does not exist"),
668 /// Returns the indentation before `span` if there are nothing but `[ \t]`
669 /// before it on its line.
670 fn indentation<T: LintContext>(cx: &T, span: Span) -> Option<String> {
671 let lo = cx.sess().source_map().lookup_char_pos(span.lo());
673 .get_line(lo.line - 1 /* line numbers in `Loc` are 1-based */)
675 if let Some((pos, _)) = line.char_indices().find(|&(_, c)| c != ' ' && c != '\t') {
676 // We can mix char and byte positions here because we only consider `[ \t]`.
677 if lo.col == CharPos(pos) {
678 Some(line[..pos].into())
688 /// Convenience extension trait for `Diagnostic`.
689 pub trait DiagnosticExt<T: LintContext> {
690 /// Suggests to add an attribute to an item.
692 /// Correctly handles indentation of the attribute and item.
697 /// diag.suggest_item_with_attr(cx, item, "#[derive(Default)]");
699 fn suggest_item_with_attr<D: Display + ?Sized>(
705 applicability: Applicability,
708 /// Suggest to add an item before another.
710 /// The item should not be indented (except for inner indentation).
715 /// diag.suggest_prepend_item(cx, item,
720 fn suggest_prepend_item(&mut self, cx: &T, item: Span, msg: &str, new_item: &str, applicability: Applicability);
722 /// Suggest to completely remove an item.
724 /// This will remove an item and all following whitespace until the next non-whitespace
725 /// character. This should work correctly if item is on the same indentation level as the
731 /// diag.suggest_remove_item(cx, item, "remove this")
733 fn suggest_remove_item(&mut self, cx: &T, item: Span, msg: &str, applicability: Applicability);
736 impl<T: LintContext> DiagnosticExt<T> for rustc_errors::Diagnostic {
737 fn suggest_item_with_attr<D: Display + ?Sized>(
743 applicability: Applicability,
745 if let Some(indent) = indentation(cx, item) {
746 let span = item.with_hi(item.lo());
748 self.span_suggestion(span, msg, format!("{attr}\n{indent}"), applicability);
752 fn suggest_prepend_item(&mut self, cx: &T, item: Span, msg: &str, new_item: &str, applicability: Applicability) {
753 if let Some(indent) = indentation(cx, item) {
754 let span = item.with_hi(item.lo());
756 let mut first = true;
757 let new_item = new_item
764 format!("{indent}{l}\n")
767 .collect::<String>();
769 self.span_suggestion(span, msg, format!("{new_item}\n{indent}"), applicability);
773 fn suggest_remove_item(&mut self, cx: &T, item: Span, msg: &str, applicability: Applicability) {
774 let mut remove_span = item;
775 let fmpos = cx.sess().source_map().lookup_byte_offset(remove_span.hi());
777 if let Some(ref src) = fmpos.sf.src {
778 let non_whitespace_offset = src[fmpos.pos.to_usize()..].find(|c| c != ' ' && c != '\t' && c != '\n');
780 if let Some(non_whitespace_offset) = non_whitespace_offset {
781 remove_span = remove_span
782 .with_hi(remove_span.hi() + BytePos(non_whitespace_offset.try_into().expect("offset too large")));
786 self.span_suggestion(remove_span, msg, "", applicability);
790 /// Suggestion results for handling closure
791 /// args dereferencing and borrowing
792 pub struct DerefClosure {
793 /// confidence on the built suggestion
794 pub applicability: Applicability,
795 /// gradually built suggestion
796 pub suggestion: String,
799 /// Build suggestion gradually by handling closure arg specific usages,
800 /// such as explicit deref and borrowing cases.
801 /// Returns `None` if no such use cases have been triggered in closure body
803 /// note: this only works on single line immutable closures with exactly one input parameter.
804 pub fn deref_closure_args(cx: &LateContext<'_>, closure: &hir::Expr<'_>) -> Option<DerefClosure> {
805 if let hir::ExprKind::Closure(&Closure { fn_decl, body, .. }) = closure.kind {
806 let closure_body = cx.tcx.hir().body(body);
807 // is closure arg a type annotated double reference (i.e.: `|x: &&i32| ...`)
808 // a type annotation is present if param `kind` is different from `TyKind::Infer`
809 let closure_arg_is_type_annotated_double_ref = if let TyKind::Rptr(_, MutTy { ty, .. }) = fn_decl.inputs[0].kind
811 matches!(ty.kind, TyKind::Rptr(_, MutTy { .. }))
816 let mut visitor = DerefDelegate {
818 closure_span: closure.span,
819 closure_arg_is_type_annotated_double_ref,
820 next_pos: closure.span.lo(),
821 suggestion_start: String::new(),
822 applicability: Applicability::MachineApplicable,
825 let fn_def_id = cx.tcx.hir().local_def_id(closure.hir_id);
826 let infcx = cx.tcx.infer_ctxt().build();
827 ExprUseVisitor::new(&mut visitor, &infcx, fn_def_id, cx.param_env, cx.typeck_results())
828 .consume_body(closure_body);
830 if !visitor.suggestion_start.is_empty() {
831 return Some(DerefClosure {
832 applicability: visitor.applicability,
833 suggestion: visitor.finish(),
840 /// Visitor struct used for tracking down
841 /// dereferencing and borrowing of closure's args
842 struct DerefDelegate<'a, 'tcx> {
843 /// The late context of the lint
844 cx: &'a LateContext<'tcx>,
845 /// The span of the input closure to adapt
847 /// Indicates if the arg of the closure is a type annotated double reference
848 closure_arg_is_type_annotated_double_ref: bool,
849 /// last position of the span to gradually build the suggestion
851 /// starting part of the gradually built suggestion
852 suggestion_start: String,
853 /// confidence on the built suggestion
854 applicability: Applicability,
857 impl<'tcx> DerefDelegate<'_, 'tcx> {
858 /// build final suggestion:
859 /// - create the ending part of suggestion
860 /// - concatenate starting and ending parts
861 /// - potentially remove needless borrowing
862 pub fn finish(&mut self) -> String {
863 let end_span = Span::new(self.next_pos, self.closure_span.hi(), self.closure_span.ctxt(), None);
864 let end_snip = snippet_with_applicability(self.cx, end_span, "..", &mut self.applicability);
865 let sugg = format!("{}{end_snip}", self.suggestion_start);
866 if self.closure_arg_is_type_annotated_double_ref {
867 sugg.replacen('&', "", 1)
873 /// indicates whether the function from `parent_expr` takes its args by double reference
874 fn func_takes_arg_by_double_ref(&self, parent_expr: &'tcx hir::Expr<'_>, cmt_hir_id: HirId) -> bool {
875 let ty = match parent_expr.kind {
876 ExprKind::MethodCall(_, receiver, call_args, _) => {
877 if let Some(sig) = self
880 .type_dependent_def_id(parent_expr.hir_id)
881 .map(|did| self.cx.tcx.fn_sig(did).skip_binder())
883 std::iter::once(receiver)
884 .chain(call_args.iter())
885 .position(|arg| arg.hir_id == cmt_hir_id)
886 .map(|i| sig.inputs()[i])
891 ExprKind::Call(func, call_args) => {
892 if let Some(sig) = expr_sig(self.cx, func) {
895 .position(|arg| arg.hir_id == cmt_hir_id)
896 .and_then(|i| sig.input(i))
897 .map(ty::Binder::skip_binder)
905 ty.map_or(false, |ty| matches!(ty.kind(), ty::Ref(_, inner, _) if inner.is_ref()))
909 impl<'tcx> Delegate<'tcx> for DerefDelegate<'_, 'tcx> {
910 fn consume(&mut self, _: &PlaceWithHirId<'tcx>, _: HirId) {}
912 fn borrow(&mut self, cmt: &PlaceWithHirId<'tcx>, _: HirId, _: ty::BorrowKind) {
913 if let PlaceBase::Local(id) = cmt.place.base {
914 let map = self.cx.tcx.hir();
915 let span = map.span(cmt.hir_id);
916 let start_span = Span::new(self.next_pos, span.lo(), span.ctxt(), None);
917 let mut start_snip = snippet_with_applicability(self.cx, start_span, "..", &mut self.applicability);
919 // identifier referring to the variable currently triggered (i.e.: `fp`)
920 let ident_str = map.name(id).to_string();
921 // full identifier that includes projection (i.e.: `fp.field`)
922 let ident_str_with_proj = snippet(self.cx, span, "..").to_string();
924 if cmt.place.projections.is_empty() {
925 // handle item without any projection, that needs an explicit borrowing
926 // i.e.: suggest `&x` instead of `x`
927 let _ = write!(self.suggestion_start, "{start_snip}&{ident_str}");
929 // cases where a parent `Call` or `MethodCall` is using the item
930 // i.e.: suggest `.contains(&x)` for `.find(|x| [1, 2, 3].contains(x)).is_none()`
932 // Note about method calls:
933 // - compiler automatically dereference references if the target type is a reference (works also for
935 // - `self` arguments in the case of `x.is_something()` are also automatically (de)referenced, and
936 // no projection should be suggested
937 if let Some(parent_expr) = get_parent_expr_for_hir(self.cx, cmt.hir_id) {
938 match &parent_expr.kind {
939 // given expression is the self argument and will be handled completely by the compiler
940 // i.e.: `|x| x.is_something()`
941 ExprKind::MethodCall(_, self_expr, ..) if self_expr.hir_id == cmt.hir_id => {
942 let _ = write!(self.suggestion_start, "{start_snip}{ident_str_with_proj}");
943 self.next_pos = span.hi();
946 // item is used in a call
947 // i.e.: `Call`: `|x| please(x)` or `MethodCall`: `|x| [1, 2, 3].contains(x)`
948 ExprKind::Call(_, [call_args @ ..]) | ExprKind::MethodCall(_, _, [call_args @ ..], _) => {
949 let expr = self.cx.tcx.hir().expect_expr(cmt.hir_id);
950 let arg_ty_kind = self.cx.typeck_results().expr_ty(expr).kind();
952 if matches!(arg_ty_kind, ty::Ref(_, _, Mutability::Not)) {
953 // suggest ampersand if call function is taking args by double reference
954 let takes_arg_by_double_ref =
955 self.func_takes_arg_by_double_ref(parent_expr, cmt.hir_id);
957 // compiler will automatically dereference field or index projection, so no need
958 // to suggest ampersand, but full identifier that includes projection is required
959 let has_field_or_index_projection =
960 cmt.place.projections.iter().any(|proj| {
961 matches!(proj.kind, ProjectionKind::Field(..) | ProjectionKind::Index)
964 // no need to bind again if the function doesn't take arg by double ref
965 // and if the item is already a double ref
966 let ident_sugg = if !call_args.is_empty()
967 && !takes_arg_by_double_ref
968 && (self.closure_arg_is_type_annotated_double_ref || has_field_or_index_projection)
970 let ident = if has_field_or_index_projection {
975 format!("{start_snip}{ident}")
977 format!("{start_snip}&{ident_str}")
979 self.suggestion_start.push_str(&ident_sugg);
980 self.next_pos = span.hi();
984 self.applicability = Applicability::Unspecified;
990 let mut replacement_str = ident_str;
991 let mut projections_handled = false;
992 cmt.place.projections.iter().enumerate().for_each(|(i, proj)| {
994 // Field projection like `|v| v.foo`
995 // no adjustment needed here, as field projections are handled by the compiler
996 ProjectionKind::Field(..) => match cmt.place.ty_before_projection(i).kind() {
997 ty::Adt(..) | ty::Tuple(_) => {
998 replacement_str = ident_str_with_proj.clone();
999 projections_handled = true;
1003 // Index projection like `|x| foo[x]`
1004 // the index is dropped so we can't get it to build the suggestion,
1005 // so the span is set-up again to get more code, using `span.hi()` (i.e.: `foo[x]`)
1006 // instead of `span.lo()` (i.e.: `foo`)
1007 ProjectionKind::Index => {
1008 let start_span = Span::new(self.next_pos, span.hi(), span.ctxt(), None);
1009 start_snip = snippet_with_applicability(self.cx, start_span, "..", &mut self.applicability);
1010 replacement_str.clear();
1011 projections_handled = true;
1013 // note: unable to trigger `Subslice` kind in tests
1014 ProjectionKind::Subslice => (),
1015 ProjectionKind::Deref => {
1016 // Explicit derefs are typically handled later on, but
1017 // some items do not need explicit deref, such as array accesses,
1018 // so we mark them as already processed
1019 // i.e.: don't suggest `*sub[1..4].len()` for `|sub| sub[1..4].len() == 3`
1020 if let ty::Ref(_, inner, _) = cmt.place.ty_before_projection(i).kind() {
1021 if matches!(inner.kind(), ty::Ref(_, innermost, _) if innermost.is_array()) {
1022 projections_handled = true;
1029 // handle `ProjectionKind::Deref` by removing one explicit deref
1030 // if no special case was detected (i.e.: suggest `*x` instead of `**x`)
1031 if !projections_handled {
1032 let last_deref = cmt
1036 .rposition(|proj| proj.kind == ProjectionKind::Deref);
1038 if let Some(pos) = last_deref {
1039 let mut projections = cmt.place.projections.clone();
1040 projections.truncate(pos);
1042 for item in projections {
1043 if item.kind == ProjectionKind::Deref {
1044 replacement_str = format!("*{replacement_str}");
1050 let _ = write!(self.suggestion_start, "{start_snip}{replacement_str}");
1052 self.next_pos = span.hi();
1056 fn mutate(&mut self, _: &PlaceWithHirId<'tcx>, _: HirId) {}
1058 fn fake_read(&mut self, _: &PlaceWithHirId<'tcx>, _: FakeReadCause, _: HirId) {}
1065 use rustc_ast::util::parser::AssocOp;
1066 use std::borrow::Cow;
1068 const SUGGESTION: Sugg<'static> = Sugg::NonParen(Cow::Borrowed("function_call()"));
1071 fn make_return_transform_sugg_into_a_return_call() {
1072 assert_eq!("return function_call()", SUGGESTION.make_return().to_string());
1076 fn blockify_transforms_sugg_into_a_block() {
1077 assert_eq!("{ function_call() }", SUGGESTION.blockify().to_string());
1081 fn binop_maybe_par() {
1082 let sugg = Sugg::BinOp(AssocOp::Add, "1".into(), "1".into());
1083 assert_eq!("(1 + 1)", sugg.maybe_par().to_string());
1085 let sugg = Sugg::BinOp(AssocOp::Add, "(1 + 1)".into(), "(1 + 1)".into());
1086 assert_eq!("((1 + 1) + (1 + 1))", sugg.maybe_par().to_string());
1090 use AssocOp::{Add, Equal, Greater, GreaterEqual, LAnd, LOr, Less, LessEqual, NotEqual};
1092 fn test_not(op: AssocOp, correct: &str) {
1093 let sugg = Sugg::BinOp(op, "x".into(), "y".into());
1094 assert_eq!((!sugg).to_string(), correct);
1097 // Invert the comparison operator.
1098 test_not(Equal, "x != y");
1099 test_not(NotEqual, "x == y");
1100 test_not(Less, "x >= y");
1101 test_not(LessEqual, "x > y");
1102 test_not(Greater, "x <= y");
1103 test_not(GreaterEqual, "x < y");
1105 // Other operators are inverted like !(..).
1106 test_not(Add, "!(x + y)");
1107 test_not(LAnd, "!(x && y)");
1108 test_not(LOr, "!(x || y)");