1 //! Contains utility functions to generate suggestions.
2 #![deny(clippy::missing_docs_in_private_items)]
4 use crate::source::{snippet, snippet_opt, snippet_with_applicability, snippet_with_macro_callsite};
5 use crate::ty::expr_sig;
6 use crate::{get_parent_expr_for_hir, higher};
7 use rustc_ast::util::parser::AssocOp;
8 use rustc_ast::{ast, token};
9 use rustc_ast_pretty::pprust::token_kind_to_string;
10 use rustc_errors::Applicability;
12 use rustc_hir::{Closure, ExprKind, HirId, MutTy, TyKind};
13 use rustc_infer::infer::TyCtxtInferExt;
14 use rustc_lint::{EarlyContext, LateContext, LintContext};
15 use rustc_middle::hir::place::ProjectionKind;
16 use rustc_middle::mir::{FakeReadCause, Mutability};
18 use rustc_span::source_map::{BytePos, CharPos, Pos, Span, SyntaxContext};
19 use rustc_typeck::expr_use_visitor::{Delegate, ExprUseVisitor, PlaceBase, PlaceWithHirId};
21 use std::fmt::{Display, Write as _};
22 use std::ops::{Add, Neg, Not, Sub};
24 /// A helper type to build suggestion correctly handling parentheses.
25 #[derive(Clone, PartialEq)]
27 /// An expression that never needs parentheses such as `1337` or `[0; 42]`.
28 NonParen(Cow<'a, str>),
29 /// An expression that does not fit in other variants.
30 MaybeParen(Cow<'a, str>),
31 /// A binary operator expression, including `as`-casts and explicit type
33 BinOp(AssocOp, Cow<'a, str>, Cow<'a, str>),
36 /// Literal constant `0`, for convenience.
37 pub const ZERO: Sugg<'static> = Sugg::NonParen(Cow::Borrowed("0"));
38 /// Literal constant `1`, for convenience.
39 pub const ONE: Sugg<'static> = Sugg::NonParen(Cow::Borrowed("1"));
40 /// a constant represents an empty string, for convenience.
41 pub const EMPTY: Sugg<'static> = Sugg::NonParen(Cow::Borrowed(""));
43 impl Display for Sugg<'_> {
44 fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
46 Sugg::NonParen(ref s) | Sugg::MaybeParen(ref s) => s.fmt(f),
47 Sugg::BinOp(op, ref lhs, ref rhs) => binop_to_string(op, lhs, rhs).fmt(f),
52 #[expect(clippy::wrong_self_convention)] // ok, because of the function `as_ty` method
54 /// Prepare a suggestion from an expression.
55 pub fn hir_opt(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option<Self> {
56 let get_snippet = |span| snippet(cx, span, "");
57 snippet_opt(cx, expr.span).map(|_| Self::hir_from_snippet(expr, get_snippet))
60 /// Convenience function around `hir_opt` for suggestions with a default
62 pub fn hir(cx: &LateContext<'_>, expr: &hir::Expr<'_>, default: &'a str) -> Self {
63 Self::hir_opt(cx, expr).unwrap_or(Sugg::NonParen(Cow::Borrowed(default)))
66 /// Same as `hir`, but it adapts the applicability level by following rules:
68 /// - Applicability level `Unspecified` will never be changed.
69 /// - If the span is inside a macro, change the applicability level to `MaybeIncorrect`.
70 /// - If the default value is used and the applicability level is `MachineApplicable`, change it
73 pub fn hir_with_applicability(
77 applicability: &mut Applicability,
79 if *applicability != Applicability::Unspecified && expr.span.from_expansion() {
80 *applicability = Applicability::MaybeIncorrect;
82 Self::hir_opt(cx, expr).unwrap_or_else(|| {
83 if *applicability == Applicability::MachineApplicable {
84 *applicability = Applicability::HasPlaceholders;
86 Sugg::NonParen(Cow::Borrowed(default))
90 /// Same as `hir`, but will use the pre expansion span if the `expr` was in a macro.
91 pub fn hir_with_macro_callsite(cx: &LateContext<'_>, expr: &hir::Expr<'_>, default: &'a str) -> Self {
92 let get_snippet = |span| snippet_with_macro_callsite(cx, span, default);
93 Self::hir_from_snippet(expr, get_snippet)
96 /// Same as `hir`, but first walks the span up to the given context. This will result in the
97 /// macro call, rather then the expansion, if the span is from a child context. If the span is
98 /// not from a child context, it will be used directly instead.
100 /// e.g. Given the expression `&vec![]`, getting a snippet from the span for `vec![]` as a HIR
101 /// node would result in `box []`. If given the context of the address of expression, this
102 /// function will correctly get a snippet of `vec![]`.
103 pub fn hir_with_context(
104 cx: &LateContext<'_>,
105 expr: &hir::Expr<'_>,
108 applicability: &mut Applicability,
110 if expr.span.ctxt() == ctxt {
111 Self::hir_from_snippet(expr, |span| snippet(cx, span, default))
113 let snip = snippet_with_applicability(cx, expr.span, default, applicability);
118 /// Generate a suggestion for an expression with the given snippet. This is used by the `hir_*`
119 /// function variants of `Sugg`, since these use different snippet functions.
120 fn hir_from_snippet(expr: &hir::Expr<'_>, get_snippet: impl Fn(Span) -> Cow<'a, str>) -> Self {
121 if let Some(range) = higher::Range::hir(expr) {
122 let op = match range.limits {
123 ast::RangeLimits::HalfOpen => AssocOp::DotDot,
124 ast::RangeLimits::Closed => AssocOp::DotDotEq,
126 let start = range.start.map_or("".into(), |expr| get_snippet(expr.span));
127 let end = range.end.map_or("".into(), |expr| get_snippet(expr.span));
129 return Sugg::BinOp(op, start, end);
133 hir::ExprKind::AddrOf(..)
134 | hir::ExprKind::Box(..)
135 | hir::ExprKind::If(..)
136 | hir::ExprKind::Let(..)
137 | hir::ExprKind::Closure { .. }
138 | hir::ExprKind::Unary(..)
139 | hir::ExprKind::Match(..) => Sugg::MaybeParen(get_snippet(expr.span)),
140 hir::ExprKind::Continue(..)
141 | hir::ExprKind::Yield(..)
142 | hir::ExprKind::Array(..)
143 | hir::ExprKind::Block(..)
144 | hir::ExprKind::Break(..)
145 | hir::ExprKind::Call(..)
146 | hir::ExprKind::Field(..)
147 | hir::ExprKind::Index(..)
148 | hir::ExprKind::InlineAsm(..)
149 | hir::ExprKind::ConstBlock(..)
150 | hir::ExprKind::Lit(..)
151 | hir::ExprKind::Loop(..)
152 | hir::ExprKind::MethodCall(..)
153 | hir::ExprKind::Path(..)
154 | hir::ExprKind::Repeat(..)
155 | hir::ExprKind::Ret(..)
156 | hir::ExprKind::Struct(..)
157 | hir::ExprKind::Tup(..)
158 | hir::ExprKind::DropTemps(_)
159 | hir::ExprKind::Err => Sugg::NonParen(get_snippet(expr.span)),
160 hir::ExprKind::Assign(lhs, rhs, _) => {
161 Sugg::BinOp(AssocOp::Assign, get_snippet(lhs.span), get_snippet(rhs.span))
163 hir::ExprKind::AssignOp(op, lhs, rhs) => {
164 Sugg::BinOp(hirbinop2assignop(op), get_snippet(lhs.span), get_snippet(rhs.span))
166 hir::ExprKind::Binary(op, lhs, rhs) => Sugg::BinOp(
167 AssocOp::from_ast_binop(op.node.into()),
168 get_snippet(lhs.span),
169 get_snippet(rhs.span),
171 hir::ExprKind::Cast(lhs, ty) => Sugg::BinOp(AssocOp::As, get_snippet(lhs.span), get_snippet(ty.span)),
172 hir::ExprKind::Type(lhs, ty) => Sugg::BinOp(AssocOp::Colon, get_snippet(lhs.span), get_snippet(ty.span)),
176 /// Prepare a suggestion from an expression.
177 pub fn ast(cx: &EarlyContext<'_>, expr: &ast::Expr, default: &'a str) -> Self {
178 use rustc_ast::ast::RangeLimits;
180 let get_whole_snippet = || {
181 if expr.span.from_expansion() {
182 snippet_with_macro_callsite(cx, expr.span, default)
184 snippet(cx, expr.span, default)
189 ast::ExprKind::AddrOf(..)
190 | ast::ExprKind::Box(..)
191 | ast::ExprKind::Closure { .. }
192 | ast::ExprKind::If(..)
193 | ast::ExprKind::Let(..)
194 | ast::ExprKind::Unary(..)
195 | ast::ExprKind::Match(..) => Sugg::MaybeParen(get_whole_snippet()),
196 ast::ExprKind::Async(..)
197 | ast::ExprKind::Block(..)
198 | ast::ExprKind::Break(..)
199 | ast::ExprKind::Call(..)
200 | ast::ExprKind::Continue(..)
201 | ast::ExprKind::Yield(..)
202 | ast::ExprKind::Field(..)
203 | ast::ExprKind::ForLoop(..)
204 | ast::ExprKind::Index(..)
205 | ast::ExprKind::InlineAsm(..)
206 | ast::ExprKind::ConstBlock(..)
207 | ast::ExprKind::Lit(..)
208 | ast::ExprKind::Loop(..)
209 | ast::ExprKind::MacCall(..)
210 | ast::ExprKind::MethodCall(..)
211 | ast::ExprKind::Paren(..)
212 | ast::ExprKind::Underscore
213 | ast::ExprKind::Path(..)
214 | ast::ExprKind::Repeat(..)
215 | ast::ExprKind::Ret(..)
216 | ast::ExprKind::Yeet(..)
217 | ast::ExprKind::Struct(..)
218 | ast::ExprKind::Try(..)
219 | ast::ExprKind::TryBlock(..)
220 | ast::ExprKind::Tup(..)
221 | ast::ExprKind::Array(..)
222 | ast::ExprKind::While(..)
223 | ast::ExprKind::Await(..)
224 | ast::ExprKind::Err => Sugg::NonParen(get_whole_snippet()),
225 ast::ExprKind::Range(ref lhs, ref rhs, RangeLimits::HalfOpen) => Sugg::BinOp(
227 lhs.as_ref().map_or("".into(), |lhs| snippet(cx, lhs.span, default)),
228 rhs.as_ref().map_or("".into(), |rhs| snippet(cx, rhs.span, default)),
230 ast::ExprKind::Range(ref lhs, ref rhs, RangeLimits::Closed) => Sugg::BinOp(
232 lhs.as_ref().map_or("".into(), |lhs| snippet(cx, lhs.span, default)),
233 rhs.as_ref().map_or("".into(), |rhs| snippet(cx, rhs.span, default)),
235 ast::ExprKind::Assign(ref lhs, ref rhs, _) => Sugg::BinOp(
237 snippet(cx, lhs.span, default),
238 snippet(cx, rhs.span, default),
240 ast::ExprKind::AssignOp(op, ref lhs, ref rhs) => Sugg::BinOp(
241 astbinop2assignop(op),
242 snippet(cx, lhs.span, default),
243 snippet(cx, rhs.span, default),
245 ast::ExprKind::Binary(op, ref lhs, ref rhs) => Sugg::BinOp(
246 AssocOp::from_ast_binop(op.node),
247 snippet(cx, lhs.span, default),
248 snippet(cx, rhs.span, default),
250 ast::ExprKind::Cast(ref lhs, ref ty) => Sugg::BinOp(
252 snippet(cx, lhs.span, default),
253 snippet(cx, ty.span, default),
255 ast::ExprKind::Type(ref lhs, ref ty) => Sugg::BinOp(
257 snippet(cx, lhs.span, default),
258 snippet(cx, ty.span, default),
263 /// Convenience method to create the `<lhs> && <rhs>` suggestion.
264 pub fn and(self, rhs: &Self) -> Sugg<'static> {
265 make_binop(ast::BinOpKind::And, &self, rhs)
268 /// Convenience method to create the `<lhs> & <rhs>` suggestion.
269 pub fn bit_and(self, rhs: &Self) -> Sugg<'static> {
270 make_binop(ast::BinOpKind::BitAnd, &self, rhs)
273 /// Convenience method to create the `<lhs> as <rhs>` suggestion.
274 pub fn as_ty<R: Display>(self, rhs: R) -> Sugg<'static> {
275 make_assoc(AssocOp::As, &self, &Sugg::NonParen(rhs.to_string().into()))
278 /// Convenience method to create the `&<expr>` suggestion.
279 pub fn addr(self) -> Sugg<'static> {
283 /// Convenience method to create the `&mut <expr>` suggestion.
284 pub fn mut_addr(self) -> Sugg<'static> {
285 make_unop("&mut ", self)
288 /// Convenience method to create the `*<expr>` suggestion.
289 pub fn deref(self) -> Sugg<'static> {
293 /// Convenience method to create the `&*<expr>` suggestion. Currently this
294 /// is needed because `sugg.deref().addr()` produces an unnecessary set of
295 /// parentheses around the deref.
296 pub fn addr_deref(self) -> Sugg<'static> {
297 make_unop("&*", self)
300 /// Convenience method to create the `&mut *<expr>` suggestion. Currently
301 /// this is needed because `sugg.deref().mut_addr()` produces an unnecessary
302 /// set of parentheses around the deref.
303 pub fn mut_addr_deref(self) -> Sugg<'static> {
304 make_unop("&mut *", self)
307 /// Convenience method to transform suggestion into a return call
308 pub fn make_return(self) -> Sugg<'static> {
309 Sugg::NonParen(Cow::Owned(format!("return {}", self)))
312 /// Convenience method to transform suggestion into a block
313 /// where the suggestion is a trailing expression
314 pub fn blockify(self) -> Sugg<'static> {
315 Sugg::NonParen(Cow::Owned(format!("{{ {} }}", self)))
318 /// Convenience method to prefix the expression with the `async` keyword.
319 /// Can be used after `blockify` to create an async block.
320 pub fn asyncify(self) -> Sugg<'static> {
321 Sugg::NonParen(Cow::Owned(format!("async {}", self)))
324 /// Convenience method to create the `<lhs>..<rhs>` or `<lhs>...<rhs>`
326 pub fn range(self, end: &Self, limit: ast::RangeLimits) -> Sugg<'static> {
328 ast::RangeLimits::HalfOpen => make_assoc(AssocOp::DotDot, &self, end),
329 ast::RangeLimits::Closed => make_assoc(AssocOp::DotDotEq, &self, end),
333 /// Adds parentheses to any expression that might need them. Suitable to the
334 /// `self` argument of a method call
335 /// (e.g., to build `bar.foo()` or `(1 + 2).foo()`).
337 pub fn maybe_par(self) -> Self {
339 Sugg::NonParen(..) => self,
340 // `(x)` and `(x).y()` both don't need additional parens.
341 Sugg::MaybeParen(sugg) => {
342 if has_enclosing_paren(&sugg) {
343 Sugg::MaybeParen(sugg)
345 Sugg::NonParen(format!("({})", sugg).into())
348 Sugg::BinOp(op, lhs, rhs) => {
349 let sugg = binop_to_string(op, &lhs, &rhs);
350 Sugg::NonParen(format!("({})", sugg).into())
356 /// Generates a string from the operator and both sides.
357 fn binop_to_string(op: AssocOp, lhs: &str, rhs: &str) -> String {
370 | AssocOp::ShiftRight
376 | AssocOp::GreaterEqual => format!(
379 op.to_ast_binop().expect("Those are AST ops").to_string(),
382 AssocOp::Assign => format!("{} = {}", lhs, rhs),
383 AssocOp::AssignOp(op) => {
384 format!("{} {}= {}", lhs, token_kind_to_string(&token::BinOp(op)), rhs)
386 AssocOp::As => format!("{} as {}", lhs, rhs),
387 AssocOp::DotDot => format!("{}..{}", lhs, rhs),
388 AssocOp::DotDotEq => format!("{}..={}", lhs, rhs),
389 AssocOp::Colon => format!("{}: {}", lhs, rhs),
393 /// Return `true` if `sugg` is enclosed in parenthesis.
394 pub fn has_enclosing_paren(sugg: impl AsRef<str>) -> bool {
395 let mut chars = sugg.as_ref().chars();
396 if chars.next() == Some('(') {
398 for c in &mut chars {
408 chars.next().is_none()
414 /// Copied from the rust standard library, and then edited
415 macro_rules! forward_binop_impls_to_ref {
416 (impl $imp:ident, $method:ident for $t:ty, type Output = $o:ty) => {
417 impl $imp<$t> for &$t {
420 fn $method(self, other: $t) -> $o {
421 $imp::$method(self, &other)
425 impl $imp<&$t> for $t {
428 fn $method(self, other: &$t) -> $o {
429 $imp::$method(&self, other)
436 fn $method(self, other: $t) -> $o {
437 $imp::$method(&self, &other)
443 impl Add for &Sugg<'_> {
444 type Output = Sugg<'static>;
445 fn add(self, rhs: &Sugg<'_>) -> Sugg<'static> {
446 make_binop(ast::BinOpKind::Add, self, rhs)
450 impl Sub for &Sugg<'_> {
451 type Output = Sugg<'static>;
452 fn sub(self, rhs: &Sugg<'_>) -> Sugg<'static> {
453 make_binop(ast::BinOpKind::Sub, self, rhs)
457 forward_binop_impls_to_ref!(impl Add, add for Sugg<'_>, type Output = Sugg<'static>);
458 forward_binop_impls_to_ref!(impl Sub, sub for Sugg<'_>, type Output = Sugg<'static>);
460 impl Neg for Sugg<'_> {
461 type Output = Sugg<'static>;
462 fn neg(self) -> Sugg<'static> {
467 impl<'a> Not for Sugg<'a> {
468 type Output = Sugg<'a>;
469 fn not(self) -> Sugg<'a> {
470 use AssocOp::{Equal, Greater, GreaterEqual, Less, LessEqual, NotEqual};
472 if let Sugg::BinOp(op, lhs, rhs) = self {
473 let to_op = match op {
476 Less => GreaterEqual,
477 GreaterEqual => Less,
478 Greater => LessEqual,
479 LessEqual => Greater,
480 _ => return make_unop("!", Sugg::BinOp(op, lhs, rhs)),
482 Sugg::BinOp(to_op, lhs, rhs)
489 /// Helper type to display either `foo` or `(foo)`.
490 struct ParenHelper<T> {
491 /// `true` if parentheses are needed.
493 /// The main thing to display.
497 impl<T> ParenHelper<T> {
498 /// Builds a `ParenHelper`.
499 fn new(paren: bool, wrapped: T) -> Self {
500 Self { paren, wrapped }
504 impl<T: Display> Display for ParenHelper<T> {
505 fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
507 write!(f, "({})", self.wrapped)
514 /// Builds the string for `<op><expr>` adding parenthesis when necessary.
516 /// For convenience, the operator is taken as a string because all unary
517 /// operators have the same
519 pub fn make_unop(op: &str, expr: Sugg<'_>) -> Sugg<'static> {
520 Sugg::MaybeParen(format!("{}{}", op, expr.maybe_par()).into())
523 /// Builds the string for `<lhs> <op> <rhs>` adding parenthesis when necessary.
525 /// Precedence of shift operator relative to other arithmetic operation is
526 /// often confusing so
527 /// parenthesis will always be added for a mix of these.
528 pub fn make_assoc(op: AssocOp, lhs: &Sugg<'_>, rhs: &Sugg<'_>) -> Sugg<'static> {
529 /// Returns `true` if the operator is a shift operator `<<` or `>>`.
530 fn is_shift(op: AssocOp) -> bool {
531 matches!(op, AssocOp::ShiftLeft | AssocOp::ShiftRight)
534 /// Returns `true` if the operator is an arithmetic operator
535 /// (i.e., `+`, `-`, `*`, `/`, `%`).
536 fn is_arith(op: AssocOp) -> bool {
539 AssocOp::Add | AssocOp::Subtract | AssocOp::Multiply | AssocOp::Divide | AssocOp::Modulus
543 /// Returns `true` if the operator `op` needs parenthesis with the operator
544 /// `other` in the direction `dir`.
545 fn needs_paren(op: AssocOp, other: AssocOp, dir: Associativity) -> bool {
546 other.precedence() < op.precedence()
547 || (other.precedence() == op.precedence()
548 && ((op != other && associativity(op) != dir)
549 || (op == other && associativity(op) != Associativity::Both)))
550 || is_shift(op) && is_arith(other)
551 || is_shift(other) && is_arith(op)
554 let lhs_paren = if let Sugg::BinOp(lop, _, _) = *lhs {
555 needs_paren(op, lop, Associativity::Left)
560 let rhs_paren = if let Sugg::BinOp(rop, _, _) = *rhs {
561 needs_paren(op, rop, Associativity::Right)
566 let lhs = ParenHelper::new(lhs_paren, lhs).to_string();
567 let rhs = ParenHelper::new(rhs_paren, rhs).to_string();
568 Sugg::BinOp(op, lhs.into(), rhs.into())
571 /// Convenience wrapper around `make_assoc` and `AssocOp::from_ast_binop`.
572 pub fn make_binop(op: ast::BinOpKind, lhs: &Sugg<'_>, rhs: &Sugg<'_>) -> Sugg<'static> {
573 make_assoc(AssocOp::from_ast_binop(op), lhs, rhs)
576 #[derive(PartialEq, Eq, Clone, Copy)]
577 /// Operator associativity.
579 /// The operator is both left-associative and right-associative.
581 /// The operator is left-associative.
583 /// The operator is not associative.
585 /// The operator is right-associative.
589 /// Returns the associativity/fixity of an operator. The difference with
590 /// `AssocOp::fixity` is that an operator can be both left and right associative
591 /// (such as `+`: `a + b + c == (a + b) + c == a + (b + c)`.
593 /// Chained `as` and explicit `:` type coercion never need inner parenthesis so
594 /// they are considered
597 fn associativity(op: AssocOp) -> Associativity {
598 use rustc_ast::util::parser::AssocOp::{
599 Add, As, Assign, AssignOp, BitAnd, BitOr, BitXor, Colon, Divide, DotDot, DotDotEq, Equal, Greater,
600 GreaterEqual, LAnd, LOr, Less, LessEqual, Modulus, Multiply, NotEqual, ShiftLeft, ShiftRight, Subtract,
604 Assign | AssignOp(_) => Associativity::Right,
605 Add | BitAnd | BitOr | BitXor | LAnd | LOr | Multiply | As | Colon => Associativity::Both,
606 Divide | Equal | Greater | GreaterEqual | Less | LessEqual | Modulus | NotEqual | ShiftLeft | ShiftRight
607 | Subtract => Associativity::Left,
608 DotDot | DotDotEq => Associativity::None,
612 /// Converts a `hir::BinOp` to the corresponding assigning binary operator.
613 fn hirbinop2assignop(op: hir::BinOp) -> AssocOp {
614 use rustc_ast::token::BinOpToken::{And, Caret, Minus, Or, Percent, Plus, Shl, Shr, Slash, Star};
616 AssocOp::AssignOp(match op.node {
617 hir::BinOpKind::Add => Plus,
618 hir::BinOpKind::BitAnd => And,
619 hir::BinOpKind::BitOr => Or,
620 hir::BinOpKind::BitXor => Caret,
621 hir::BinOpKind::Div => Slash,
622 hir::BinOpKind::Mul => Star,
623 hir::BinOpKind::Rem => Percent,
624 hir::BinOpKind::Shl => Shl,
625 hir::BinOpKind::Shr => Shr,
626 hir::BinOpKind::Sub => Minus,
635 | hir::BinOpKind::Or => panic!("This operator does not exist"),
639 /// Converts an `ast::BinOp` to the corresponding assigning binary operator.
640 fn astbinop2assignop(op: ast::BinOp) -> AssocOp {
641 use rustc_ast::ast::BinOpKind::{
642 Add, And, BitAnd, BitOr, BitXor, Div, Eq, Ge, Gt, Le, Lt, Mul, Ne, Or, Rem, Shl, Shr, Sub,
644 use rustc_ast::token::BinOpToken;
646 AssocOp::AssignOp(match op.node {
647 Add => BinOpToken::Plus,
648 BitAnd => BinOpToken::And,
649 BitOr => BinOpToken::Or,
650 BitXor => BinOpToken::Caret,
651 Div => BinOpToken::Slash,
652 Mul => BinOpToken::Star,
653 Rem => BinOpToken::Percent,
654 Shl => BinOpToken::Shl,
655 Shr => BinOpToken::Shr,
656 Sub => BinOpToken::Minus,
657 And | Eq | Ge | Gt | Le | Lt | Ne | Or => panic!("This operator does not exist"),
661 /// Returns the indentation before `span` if there are nothing but `[ \t]`
662 /// before it on its line.
663 fn indentation<T: LintContext>(cx: &T, span: Span) -> Option<String> {
664 let lo = cx.sess().source_map().lookup_char_pos(span.lo());
666 .get_line(lo.line - 1 /* line numbers in `Loc` are 1-based */)
668 if let Some((pos, _)) = line.char_indices().find(|&(_, c)| c != ' ' && c != '\t') {
669 // We can mix char and byte positions here because we only consider `[ \t]`.
670 if lo.col == CharPos(pos) {
671 Some(line[..pos].into())
681 /// Convenience extension trait for `Diagnostic`.
682 pub trait DiagnosticExt<T: LintContext> {
683 /// Suggests to add an attribute to an item.
685 /// Correctly handles indentation of the attribute and item.
690 /// diag.suggest_item_with_attr(cx, item, "#[derive(Default)]");
692 fn suggest_item_with_attr<D: Display + ?Sized>(
698 applicability: Applicability,
701 /// Suggest to add an item before another.
703 /// The item should not be indented (except for inner indentation).
708 /// diag.suggest_prepend_item(cx, item,
713 fn suggest_prepend_item(&mut self, cx: &T, item: Span, msg: &str, new_item: &str, applicability: Applicability);
715 /// Suggest to completely remove an item.
717 /// This will remove an item and all following whitespace until the next non-whitespace
718 /// character. This should work correctly if item is on the same indentation level as the
724 /// diag.suggest_remove_item(cx, item, "remove this")
726 fn suggest_remove_item(&mut self, cx: &T, item: Span, msg: &str, applicability: Applicability);
729 impl<T: LintContext> DiagnosticExt<T> for rustc_errors::Diagnostic {
730 fn suggest_item_with_attr<D: Display + ?Sized>(
736 applicability: Applicability,
738 if let Some(indent) = indentation(cx, item) {
739 let span = item.with_hi(item.lo());
741 self.span_suggestion(span, msg, format!("{}\n{}", attr, indent), applicability);
745 fn suggest_prepend_item(&mut self, cx: &T, item: Span, msg: &str, new_item: &str, applicability: Applicability) {
746 if let Some(indent) = indentation(cx, item) {
747 let span = item.with_hi(item.lo());
749 let mut first = true;
750 let new_item = new_item
757 format!("{}{}\n", indent, l)
760 .collect::<String>();
762 self.span_suggestion(span, msg, format!("{}\n{}", new_item, indent), applicability);
766 fn suggest_remove_item(&mut self, cx: &T, item: Span, msg: &str, applicability: Applicability) {
767 let mut remove_span = item;
768 let hi = cx.sess().source_map().next_point(remove_span).hi();
769 let fmpos = cx.sess().source_map().lookup_byte_offset(hi);
771 if let Some(ref src) = fmpos.sf.src {
772 let non_whitespace_offset = src[fmpos.pos.to_usize()..].find(|c| c != ' ' && c != '\t' && c != '\n');
774 if let Some(non_whitespace_offset) = non_whitespace_offset {
775 remove_span = remove_span
776 .with_hi(remove_span.hi() + BytePos(non_whitespace_offset.try_into().expect("offset too large")));
780 self.span_suggestion(remove_span, msg, "", applicability);
784 /// Suggestion results for handling closure
785 /// args dereferencing and borrowing
786 pub struct DerefClosure {
787 /// confidence on the built suggestion
788 pub applicability: Applicability,
789 /// gradually built suggestion
790 pub suggestion: String,
793 /// Build suggestion gradually by handling closure arg specific usages,
794 /// such as explicit deref and borrowing cases.
795 /// Returns `None` if no such use cases have been triggered in closure body
797 /// note: this only works on single line immutable closures with exactly one input parameter.
798 pub fn deref_closure_args<'tcx>(cx: &LateContext<'_>, closure: &'tcx hir::Expr<'_>) -> Option<DerefClosure> {
799 if let hir::ExprKind::Closure(&Closure { fn_decl, body, .. }) = closure.kind {
800 let closure_body = cx.tcx.hir().body(body);
801 // is closure arg a type annotated double reference (i.e.: `|x: &&i32| ...`)
802 // a type annotation is present if param `kind` is different from `TyKind::Infer`
803 let closure_arg_is_type_annotated_double_ref = if let TyKind::Rptr(_, MutTy { ty, .. }) = fn_decl.inputs[0].kind
805 matches!(ty.kind, TyKind::Rptr(_, MutTy { .. }))
810 let mut visitor = DerefDelegate {
812 closure_span: closure.span,
813 closure_arg_is_type_annotated_double_ref,
814 next_pos: closure.span.lo(),
815 suggestion_start: String::new(),
816 applicability: Applicability::MachineApplicable,
819 let fn_def_id = cx.tcx.hir().local_def_id(closure.hir_id);
820 cx.tcx.infer_ctxt().enter(|infcx| {
821 ExprUseVisitor::new(&mut visitor, &infcx, fn_def_id, cx.param_env, cx.typeck_results())
822 .consume_body(closure_body);
825 if !visitor.suggestion_start.is_empty() {
826 return Some(DerefClosure {
827 applicability: visitor.applicability,
828 suggestion: visitor.finish(),
835 /// Visitor struct used for tracking down
836 /// dereferencing and borrowing of closure's args
837 struct DerefDelegate<'a, 'tcx> {
838 /// The late context of the lint
839 cx: &'a LateContext<'tcx>,
840 /// The span of the input closure to adapt
842 /// Indicates if the arg of the closure is a type annotated double reference
843 closure_arg_is_type_annotated_double_ref: bool,
844 /// last position of the span to gradually build the suggestion
846 /// starting part of the gradually built suggestion
847 suggestion_start: String,
848 /// confidence on the built suggestion
849 applicability: Applicability,
852 impl<'tcx> DerefDelegate<'_, 'tcx> {
853 /// build final suggestion:
854 /// - create the ending part of suggestion
855 /// - concatenate starting and ending parts
856 /// - potentially remove needless borrowing
857 pub fn finish(&mut self) -> String {
858 let end_span = Span::new(self.next_pos, self.closure_span.hi(), self.closure_span.ctxt(), None);
859 let end_snip = snippet_with_applicability(self.cx, end_span, "..", &mut self.applicability);
860 let sugg = format!("{}{}", self.suggestion_start, end_snip);
861 if self.closure_arg_is_type_annotated_double_ref {
862 sugg.replacen('&', "", 1)
868 /// indicates whether the function from `parent_expr` takes its args by double reference
869 fn func_takes_arg_by_double_ref(&self, parent_expr: &'tcx hir::Expr<'_>, cmt_hir_id: HirId) -> bool {
870 let ty = match parent_expr.kind {
871 ExprKind::MethodCall(_, call_args, _) => {
872 if let Some(sig) = self
875 .type_dependent_def_id(parent_expr.hir_id)
876 .map(|did| self.cx.tcx.fn_sig(did).skip_binder())
880 .position(|arg| arg.hir_id == cmt_hir_id)
881 .map(|i| sig.inputs()[i])
886 ExprKind::Call(func, call_args) => {
887 if let Some(sig) = expr_sig(self.cx, func) {
890 .position(|arg| arg.hir_id == cmt_hir_id)
891 .and_then(|i| sig.input(i))
892 .map(ty::Binder::skip_binder)
900 ty.map_or(false, |ty| matches!(ty.kind(), ty::Ref(_, inner, _) if inner.is_ref()))
904 impl<'tcx> Delegate<'tcx> for DerefDelegate<'_, 'tcx> {
905 fn consume(&mut self, _: &PlaceWithHirId<'tcx>, _: HirId) {}
907 fn borrow(&mut self, cmt: &PlaceWithHirId<'tcx>, _: HirId, _: ty::BorrowKind) {
908 if let PlaceBase::Local(id) = cmt.place.base {
909 let map = self.cx.tcx.hir();
910 let span = map.span(cmt.hir_id);
911 let start_span = Span::new(self.next_pos, span.lo(), span.ctxt(), None);
912 let mut start_snip = snippet_with_applicability(self.cx, start_span, "..", &mut self.applicability);
914 // identifier referring to the variable currently triggered (i.e.: `fp`)
915 let ident_str = map.name(id).to_string();
916 // full identifier that includes projection (i.e.: `fp.field`)
917 let ident_str_with_proj = snippet(self.cx, span, "..").to_string();
919 if cmt.place.projections.is_empty() {
920 // handle item without any projection, that needs an explicit borrowing
921 // i.e.: suggest `&x` instead of `x`
922 let _ = write!(self.suggestion_start, "{}&{}", start_snip, ident_str);
924 // cases where a parent `Call` or `MethodCall` is using the item
925 // i.e.: suggest `.contains(&x)` for `.find(|x| [1, 2, 3].contains(x)).is_none()`
927 // Note about method calls:
928 // - compiler automatically dereference references if the target type is a reference (works also for
930 // - `self` arguments in the case of `x.is_something()` are also automatically (de)referenced, and
931 // no projection should be suggested
932 if let Some(parent_expr) = get_parent_expr_for_hir(self.cx, cmt.hir_id) {
933 match &parent_expr.kind {
934 // given expression is the self argument and will be handled completely by the compiler
935 // i.e.: `|x| x.is_something()`
936 ExprKind::MethodCall(_, [self_expr, ..], _) if self_expr.hir_id == cmt.hir_id => {
937 let _ = write!(self.suggestion_start, "{}{}", start_snip, ident_str_with_proj);
938 self.next_pos = span.hi();
941 // item is used in a call
942 // i.e.: `Call`: `|x| please(x)` or `MethodCall`: `|x| [1, 2, 3].contains(x)`
943 ExprKind::Call(_, [call_args @ ..]) | ExprKind::MethodCall(_, [_, call_args @ ..], _) => {
944 let expr = self.cx.tcx.hir().expect_expr(cmt.hir_id);
945 let arg_ty_kind = self.cx.typeck_results().expr_ty(expr).kind();
947 if matches!(arg_ty_kind, ty::Ref(_, _, Mutability::Not)) {
948 // suggest ampersand if call function is taking args by double reference
949 let takes_arg_by_double_ref =
950 self.func_takes_arg_by_double_ref(parent_expr, cmt.hir_id);
952 // compiler will automatically dereference field or index projection, so no need
953 // to suggest ampersand, but full identifier that includes projection is required
954 let has_field_or_index_projection =
955 cmt.place.projections.iter().any(|proj| {
956 matches!(proj.kind, ProjectionKind::Field(..) | ProjectionKind::Index)
959 // no need to bind again if the function doesn't take arg by double ref
960 // and if the item is already a double ref
961 let ident_sugg = if !call_args.is_empty()
962 && !takes_arg_by_double_ref
963 && (self.closure_arg_is_type_annotated_double_ref || has_field_or_index_projection)
965 let ident = if has_field_or_index_projection {
970 format!("{}{}", start_snip, ident)
972 format!("{}&{}", start_snip, ident_str)
974 self.suggestion_start.push_str(&ident_sugg);
975 self.next_pos = span.hi();
979 self.applicability = Applicability::Unspecified;
985 let mut replacement_str = ident_str;
986 let mut projections_handled = false;
987 cmt.place.projections.iter().enumerate().for_each(|(i, proj)| {
989 // Field projection like `|v| v.foo`
990 // no adjustment needed here, as field projections are handled by the compiler
991 ProjectionKind::Field(..) => match cmt.place.ty_before_projection(i).kind() {
992 ty::Adt(..) | ty::Tuple(_) => {
993 replacement_str = ident_str_with_proj.clone();
994 projections_handled = true;
998 // Index projection like `|x| foo[x]`
999 // the index is dropped so we can't get it to build the suggestion,
1000 // so the span is set-up again to get more code, using `span.hi()` (i.e.: `foo[x]`)
1001 // instead of `span.lo()` (i.e.: `foo`)
1002 ProjectionKind::Index => {
1003 let start_span = Span::new(self.next_pos, span.hi(), span.ctxt(), None);
1004 start_snip = snippet_with_applicability(self.cx, start_span, "..", &mut self.applicability);
1005 replacement_str.clear();
1006 projections_handled = true;
1008 // note: unable to trigger `Subslice` kind in tests
1009 ProjectionKind::Subslice => (),
1010 ProjectionKind::Deref => {
1011 // Explicit derefs are typically handled later on, but
1012 // some items do not need explicit deref, such as array accesses,
1013 // so we mark them as already processed
1014 // i.e.: don't suggest `*sub[1..4].len()` for `|sub| sub[1..4].len() == 3`
1015 if let ty::Ref(_, inner, _) = cmt.place.ty_before_projection(i).kind() {
1016 if matches!(inner.kind(), ty::Ref(_, innermost, _) if innermost.is_array()) {
1017 projections_handled = true;
1024 // handle `ProjectionKind::Deref` by removing one explicit deref
1025 // if no special case was detected (i.e.: suggest `*x` instead of `**x`)
1026 if !projections_handled {
1027 let last_deref = cmt
1031 .rposition(|proj| proj.kind == ProjectionKind::Deref);
1033 if let Some(pos) = last_deref {
1034 let mut projections = cmt.place.projections.clone();
1035 projections.truncate(pos);
1037 for item in projections {
1038 if item.kind == ProjectionKind::Deref {
1039 replacement_str = format!("*{}", replacement_str);
1045 let _ = write!(self.suggestion_start, "{}{}", start_snip, replacement_str);
1047 self.next_pos = span.hi();
1051 fn mutate(&mut self, _: &PlaceWithHirId<'tcx>, _: HirId) {}
1053 fn fake_read(&mut self, _: &rustc_typeck::expr_use_visitor::PlaceWithHirId<'tcx>, _: FakeReadCause, _: HirId) {}
1060 use rustc_ast::util::parser::AssocOp;
1061 use std::borrow::Cow;
1063 const SUGGESTION: Sugg<'static> = Sugg::NonParen(Cow::Borrowed("function_call()"));
1066 fn make_return_transform_sugg_into_a_return_call() {
1067 assert_eq!("return function_call()", SUGGESTION.make_return().to_string());
1071 fn blockify_transforms_sugg_into_a_block() {
1072 assert_eq!("{ function_call() }", SUGGESTION.blockify().to_string());
1076 fn binop_maybe_par() {
1077 let sugg = Sugg::BinOp(AssocOp::Add, "1".into(), "1".into());
1078 assert_eq!("(1 + 1)", sugg.maybe_par().to_string());
1080 let sugg = Sugg::BinOp(AssocOp::Add, "(1 + 1)".into(), "(1 + 1)".into());
1081 assert_eq!("((1 + 1) + (1 + 1))", sugg.maybe_par().to_string());
1085 use AssocOp::{Add, Equal, Greater, GreaterEqual, LAnd, LOr, Less, LessEqual, NotEqual};
1087 fn test_not(op: AssocOp, correct: &str) {
1088 let sugg = Sugg::BinOp(op, "x".into(), "y".into());
1089 assert_eq!((!sugg).to_string(), correct);
1092 // Invert the comparison operator.
1093 test_not(Equal, "x != y");
1094 test_not(NotEqual, "x == y");
1095 test_not(Less, "x >= y");
1096 test_not(LessEqual, "x > y");
1097 test_not(Greater, "x <= y");
1098 test_not(GreaterEqual, "x < y");
1100 // Other operators are inverted like !(..).
1101 test_not(Add, "!(x + y)");
1102 test_not(LAnd, "!(x && y)");
1103 test_not(LOr, "!(x || y)");