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::{get_parent_expr_for_hir, higher};
6 use rustc_ast::util::parser::AssocOp;
7 use rustc_ast::{ast, token};
8 use rustc_ast_pretty::pprust::token_kind_to_string;
9 use rustc_errors::Applicability;
11 use rustc_hir::{ExprKind, HirId, MutTy, TyKind};
12 use rustc_infer::infer::TyCtxtInferExt;
13 use rustc_lint::{EarlyContext, LateContext, LintContext};
14 use rustc_middle::hir::place::ProjectionKind;
15 use rustc_middle::mir::{FakeReadCause, Mutability};
17 use rustc_span::source_map::{BytePos, CharPos, Pos, Span, SyntaxContext};
18 use rustc_typeck::expr_use_visitor::{Delegate, ExprUseVisitor, PlaceBase, PlaceWithHirId};
20 use std::convert::TryInto;
21 use std::fmt::Display;
23 use std::ops::{Add, Neg, Not, Sub};
25 /// A helper type to build suggestion correctly handling parentheses.
26 #[derive(Clone, PartialEq)]
28 /// An expression that never needs parentheses such as `1337` or `[0; 42]`.
29 NonParen(Cow<'a, str>),
30 /// An expression that does not fit in other variants.
31 MaybeParen(Cow<'a, str>),
32 /// A binary operator expression, including `as`-casts and explicit type
34 BinOp(AssocOp, Cow<'a, str>, Cow<'a, str>),
37 /// Literal constant `0`, for convenience.
38 pub const ZERO: Sugg<'static> = Sugg::NonParen(Cow::Borrowed("0"));
39 /// Literal constant `1`, for convenience.
40 pub const ONE: Sugg<'static> = Sugg::NonParen(Cow::Borrowed("1"));
41 /// a constant represents an empty string, for convenience.
42 pub const EMPTY: Sugg<'static> = Sugg::NonParen(Cow::Borrowed(""));
44 impl Display for Sugg<'_> {
45 fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
47 Sugg::NonParen(ref s) | Sugg::MaybeParen(ref s) => s.fmt(f),
48 Sugg::BinOp(op, ref lhs, ref rhs) => binop_to_string(op, lhs, rhs).fmt(f),
53 #[allow(clippy::wrong_self_convention)] // ok, because of the function `as_ty` method
55 /// Prepare a suggestion from an expression.
56 pub fn hir_opt(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option<Self> {
57 let get_snippet = |span| snippet(cx, span, "");
58 snippet_opt(cx, expr.span).map(|_| Self::hir_from_snippet(expr, get_snippet))
61 /// Convenience function around `hir_opt` for suggestions with a default
63 pub fn hir(cx: &LateContext<'_>, expr: &hir::Expr<'_>, default: &'a str) -> Self {
64 Self::hir_opt(cx, expr).unwrap_or(Sugg::NonParen(Cow::Borrowed(default)))
67 /// Same as `hir`, but it adapts the applicability level by following rules:
69 /// - Applicability level `Unspecified` will never be changed.
70 /// - If the span is inside a macro, change the applicability level to `MaybeIncorrect`.
71 /// - If the default value is used and the applicability level is `MachineApplicable`, change it
74 pub fn hir_with_applicability(
78 applicability: &mut Applicability,
80 if *applicability != Applicability::Unspecified && expr.span.from_expansion() {
81 *applicability = Applicability::MaybeIncorrect;
83 Self::hir_opt(cx, expr).unwrap_or_else(|| {
84 if *applicability == Applicability::MachineApplicable {
85 *applicability = Applicability::HasPlaceholders;
87 Sugg::NonParen(Cow::Borrowed(default))
91 /// Same as `hir`, but will use the pre expansion span if the `expr` was in a macro.
92 pub fn hir_with_macro_callsite(cx: &LateContext<'_>, expr: &hir::Expr<'_>, default: &'a str) -> Self {
93 let get_snippet = |span| snippet_with_macro_callsite(cx, span, default);
94 Self::hir_from_snippet(expr, get_snippet)
97 /// Same as `hir`, but first walks the span up to the given context. This will result in the
98 /// macro call, rather then the expansion, if the span is from a child context. If the span is
99 /// not from a child context, it will be used directly instead.
101 /// e.g. Given the expression `&vec![]`, getting a snippet from the span for `vec![]` as a HIR
102 /// node would result in `box []`. If given the context of the address of expression, this
103 /// function will correctly get a snippet of `vec![]`.
104 pub fn hir_with_context(
105 cx: &LateContext<'_>,
106 expr: &hir::Expr<'_>,
109 applicability: &mut Applicability,
111 if expr.span.ctxt() == ctxt {
112 Self::hir_from_snippet(expr, |span| snippet(cx, span, default))
114 let snip = snippet_with_applicability(cx, expr.span, default, applicability);
119 /// Generate a suggestion for an expression with the given snippet. This is used by the `hir_*`
120 /// function variants of `Sugg`, since these use different snippet functions.
121 fn hir_from_snippet(expr: &hir::Expr<'_>, get_snippet: impl Fn(Span) -> Cow<'a, str>) -> Self {
122 if let Some(range) = higher::Range::hir(expr) {
123 let op = match range.limits {
124 ast::RangeLimits::HalfOpen => AssocOp::DotDot,
125 ast::RangeLimits::Closed => AssocOp::DotDotEq,
127 let start = range.start.map_or("".into(), |expr| get_snippet(expr.span));
128 let end = range.end.map_or("".into(), |expr| get_snippet(expr.span));
130 return Sugg::BinOp(op, start, end);
134 hir::ExprKind::AddrOf(..)
135 | hir::ExprKind::Box(..)
136 | hir::ExprKind::If(..)
137 | hir::ExprKind::Let(..)
138 | hir::ExprKind::Closure(..)
139 | hir::ExprKind::Unary(..)
140 | hir::ExprKind::Match(..) => Sugg::MaybeParen(get_snippet(expr.span)),
141 hir::ExprKind::Continue(..)
142 | hir::ExprKind::Yield(..)
143 | hir::ExprKind::Array(..)
144 | hir::ExprKind::Block(..)
145 | hir::ExprKind::Break(..)
146 | hir::ExprKind::Call(..)
147 | hir::ExprKind::Field(..)
148 | hir::ExprKind::Index(..)
149 | hir::ExprKind::InlineAsm(..)
150 | hir::ExprKind::LlvmInlineAsm(..)
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::DropTemps(_)
161 | hir::ExprKind::Err => Sugg::NonParen(get_snippet(expr.span)),
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 get_whole_snippet = || {
183 if expr.span.from_expansion() {
184 snippet_with_macro_callsite(cx, expr.span, default)
186 snippet(cx, expr.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(get_whole_snippet()),
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::LlvmInlineAsm(..)
209 | ast::ExprKind::ConstBlock(..)
210 | ast::ExprKind::Lit(..)
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::Struct(..)
220 | ast::ExprKind::Try(..)
221 | ast::ExprKind::TryBlock(..)
222 | ast::ExprKind::Tup(..)
223 | ast::ExprKind::Array(..)
224 | ast::ExprKind::While(..)
225 | ast::ExprKind::Await(..)
226 | ast::ExprKind::Err => Sugg::NonParen(get_whole_snippet()),
227 ast::ExprKind::Range(ref lhs, ref rhs, RangeLimits::HalfOpen) => Sugg::BinOp(
229 lhs.as_ref().map_or("".into(), |lhs| snippet(cx, lhs.span, default)),
230 rhs.as_ref().map_or("".into(), |rhs| snippet(cx, rhs.span, default)),
232 ast::ExprKind::Range(ref lhs, ref rhs, RangeLimits::Closed) => Sugg::BinOp(
234 lhs.as_ref().map_or("".into(), |lhs| snippet(cx, lhs.span, default)),
235 rhs.as_ref().map_or("".into(), |rhs| snippet(cx, rhs.span, default)),
237 ast::ExprKind::Assign(ref lhs, ref rhs, _) => Sugg::BinOp(
239 snippet(cx, lhs.span, default),
240 snippet(cx, rhs.span, default),
242 ast::ExprKind::AssignOp(op, ref lhs, ref rhs) => Sugg::BinOp(
243 astbinop2assignop(op),
244 snippet(cx, lhs.span, default),
245 snippet(cx, rhs.span, default),
247 ast::ExprKind::Binary(op, ref lhs, ref rhs) => Sugg::BinOp(
248 AssocOp::from_ast_binop(op.node),
249 snippet(cx, lhs.span, default),
250 snippet(cx, rhs.span, default),
252 ast::ExprKind::Cast(ref lhs, ref ty) => Sugg::BinOp(
254 snippet(cx, lhs.span, default),
255 snippet(cx, ty.span, default),
257 ast::ExprKind::Type(ref lhs, ref ty) => Sugg::BinOp(
259 snippet(cx, lhs.span, default),
260 snippet(cx, ty.span, default),
265 /// Convenience method to create the `<lhs> && <rhs>` suggestion.
266 pub fn and(self, rhs: &Self) -> Sugg<'static> {
267 make_binop(ast::BinOpKind::And, &self, rhs)
270 /// Convenience method to create the `<lhs> & <rhs>` suggestion.
271 pub fn bit_and(self, rhs: &Self) -> Sugg<'static> {
272 make_binop(ast::BinOpKind::BitAnd, &self, rhs)
275 /// Convenience method to create the `<lhs> as <rhs>` suggestion.
276 pub fn as_ty<R: Display>(self, rhs: R) -> Sugg<'static> {
277 make_assoc(AssocOp::As, &self, &Sugg::NonParen(rhs.to_string().into()))
280 /// Convenience method to create the `&<expr>` suggestion.
281 pub fn addr(self) -> Sugg<'static> {
285 /// Convenience method to create the `&mut <expr>` suggestion.
286 pub fn mut_addr(self) -> Sugg<'static> {
287 make_unop("&mut ", self)
290 /// Convenience method to create the `*<expr>` suggestion.
291 pub fn deref(self) -> Sugg<'static> {
295 /// Convenience method to create the `&*<expr>` suggestion. Currently this
296 /// is needed because `sugg.deref().addr()` produces an unnecessary set of
297 /// parentheses around the deref.
298 pub fn addr_deref(self) -> Sugg<'static> {
299 make_unop("&*", self)
302 /// Convenience method to create the `&mut *<expr>` suggestion. Currently
303 /// this is needed because `sugg.deref().mut_addr()` produces an unnecessary
304 /// set of parentheses around the deref.
305 pub fn mut_addr_deref(self) -> Sugg<'static> {
306 make_unop("&mut *", self)
309 /// Convenience method to transform suggestion into a return call
310 pub fn make_return(self) -> Sugg<'static> {
311 Sugg::NonParen(Cow::Owned(format!("return {}", self)))
314 /// Convenience method to transform suggestion into a block
315 /// where the suggestion is a trailing expression
316 pub fn blockify(self) -> Sugg<'static> {
317 Sugg::NonParen(Cow::Owned(format!("{{ {} }}", self)))
320 /// Convenience method to create the `<lhs>..<rhs>` or `<lhs>...<rhs>`
323 pub fn range(self, end: &Self, limit: ast::RangeLimits) -> Sugg<'static> {
325 ast::RangeLimits::HalfOpen => make_assoc(AssocOp::DotDot, &self, end),
326 ast::RangeLimits::Closed => make_assoc(AssocOp::DotDotEq, &self, end),
330 /// Adds parentheses to any expression that might need them. Suitable to the
331 /// `self` argument of a method call
332 /// (e.g., to build `bar.foo()` or `(1 + 2).foo()`).
334 pub fn maybe_par(self) -> Self {
336 Sugg::NonParen(..) => self,
337 // `(x)` and `(x).y()` both don't need additional parens.
338 Sugg::MaybeParen(sugg) => {
339 if has_enclosing_paren(&sugg) {
340 Sugg::MaybeParen(sugg)
342 Sugg::NonParen(format!("({})", sugg).into())
345 Sugg::BinOp(op, lhs, rhs) => {
346 let sugg = binop_to_string(op, &lhs, &rhs);
347 Sugg::NonParen(format!("({})", sugg).into())
353 /// Generates a string from the operator and both sides.
354 fn binop_to_string(op: AssocOp, lhs: &str, rhs: &str) -> String {
367 | AssocOp::ShiftRight
373 | AssocOp::GreaterEqual => format!(
376 op.to_ast_binop().expect("Those are AST ops").to_string(),
379 AssocOp::Assign => format!("{} = {}", lhs, rhs),
380 AssocOp::AssignOp(op) => {
381 format!("{} {}= {}", lhs, token_kind_to_string(&token::BinOp(op)), rhs)
383 AssocOp::As => format!("{} as {}", lhs, rhs),
384 AssocOp::DotDot => format!("{}..{}", lhs, rhs),
385 AssocOp::DotDotEq => format!("{}..={}", lhs, rhs),
386 AssocOp::Colon => format!("{}: {}", lhs, rhs),
390 /// Return `true` if `sugg` is enclosed in parenthesis.
391 fn has_enclosing_paren(sugg: impl AsRef<str>) -> bool {
392 let mut chars = sugg.as_ref().chars();
393 if chars.next() == Some('(') {
395 for c in &mut chars {
405 chars.next().is_none()
411 /// Copied from the rust standard library, and then edited
412 macro_rules! forward_binop_impls_to_ref {
413 (impl $imp:ident, $method:ident for $t:ty, type Output = $o:ty) => {
414 impl $imp<$t> for &$t {
417 fn $method(self, other: $t) -> $o {
418 $imp::$method(self, &other)
422 impl $imp<&$t> for $t {
425 fn $method(self, other: &$t) -> $o {
426 $imp::$method(&self, other)
433 fn $method(self, other: $t) -> $o {
434 $imp::$method(&self, &other)
440 impl Add for &Sugg<'_> {
441 type Output = Sugg<'static>;
442 fn add(self, rhs: &Sugg<'_>) -> Sugg<'static> {
443 make_binop(ast::BinOpKind::Add, self, rhs)
447 impl Sub for &Sugg<'_> {
448 type Output = Sugg<'static>;
449 fn sub(self, rhs: &Sugg<'_>) -> Sugg<'static> {
450 make_binop(ast::BinOpKind::Sub, self, rhs)
454 forward_binop_impls_to_ref!(impl Add, add for Sugg<'_>, type Output = Sugg<'static>);
455 forward_binop_impls_to_ref!(impl Sub, sub for Sugg<'_>, type Output = Sugg<'static>);
457 impl Neg for Sugg<'_> {
458 type Output = Sugg<'static>;
459 fn neg(self) -> Sugg<'static> {
464 impl<'a> Not for Sugg<'a> {
465 type Output = Sugg<'a>;
466 fn not(self) -> Sugg<'a> {
467 use AssocOp::{Equal, Greater, GreaterEqual, Less, LessEqual, NotEqual};
469 if let Sugg::BinOp(op, lhs, rhs) = self {
470 let to_op = match op {
473 Less => GreaterEqual,
474 GreaterEqual => Less,
475 Greater => LessEqual,
476 LessEqual => Greater,
477 _ => return make_unop("!", Sugg::BinOp(op, lhs, rhs)),
479 Sugg::BinOp(to_op, lhs, rhs)
486 /// Helper type to display either `foo` or `(foo)`.
487 struct ParenHelper<T> {
488 /// `true` if parentheses are needed.
490 /// The main thing to display.
494 impl<T> ParenHelper<T> {
495 /// Builds a `ParenHelper`.
496 fn new(paren: bool, wrapped: T) -> Self {
497 Self { paren, wrapped }
501 impl<T: Display> Display for ParenHelper<T> {
502 fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
504 write!(f, "({})", self.wrapped)
511 /// Builds the string for `<op><expr>` adding parenthesis when necessary.
513 /// For convenience, the operator is taken as a string because all unary
514 /// operators have the same
516 pub fn make_unop(op: &str, expr: Sugg<'_>) -> Sugg<'static> {
517 Sugg::MaybeParen(format!("{}{}", op, expr.maybe_par()).into())
520 /// Builds the string for `<lhs> <op> <rhs>` adding parenthesis when necessary.
522 /// Precedence of shift operator relative to other arithmetic operation is
523 /// often confusing so
524 /// parenthesis will always be added for a mix of these.
525 pub fn make_assoc(op: AssocOp, lhs: &Sugg<'_>, rhs: &Sugg<'_>) -> Sugg<'static> {
526 /// Returns `true` if the operator is a shift operator `<<` or `>>`.
527 fn is_shift(op: AssocOp) -> bool {
528 matches!(op, AssocOp::ShiftLeft | AssocOp::ShiftRight)
531 /// Returns `true` if the operator is an arithmetic operator
532 /// (i.e., `+`, `-`, `*`, `/`, `%`).
533 fn is_arith(op: AssocOp) -> bool {
536 AssocOp::Add | AssocOp::Subtract | AssocOp::Multiply | AssocOp::Divide | AssocOp::Modulus
540 /// Returns `true` if the operator `op` needs parenthesis with the operator
541 /// `other` in the direction `dir`.
542 fn needs_paren(op: AssocOp, other: AssocOp, dir: Associativity) -> bool {
543 other.precedence() < op.precedence()
544 || (other.precedence() == op.precedence()
545 && ((op != other && associativity(op) != dir)
546 || (op == other && associativity(op) != Associativity::Both)))
547 || is_shift(op) && is_arith(other)
548 || is_shift(other) && is_arith(op)
551 let lhs_paren = if let Sugg::BinOp(lop, _, _) = *lhs {
552 needs_paren(op, lop, Associativity::Left)
557 let rhs_paren = if let Sugg::BinOp(rop, _, _) = *rhs {
558 needs_paren(op, rop, Associativity::Right)
563 let lhs = ParenHelper::new(lhs_paren, lhs).to_string();
564 let rhs = ParenHelper::new(rhs_paren, rhs).to_string();
565 Sugg::BinOp(op, lhs.into(), rhs.into())
568 /// Convenience wrapper around `make_assoc` and `AssocOp::from_ast_binop`.
569 pub fn make_binop(op: ast::BinOpKind, lhs: &Sugg<'_>, rhs: &Sugg<'_>) -> Sugg<'static> {
570 make_assoc(AssocOp::from_ast_binop(op), lhs, rhs)
573 #[derive(PartialEq, Eq, Clone, Copy)]
574 /// Operator associativity.
576 /// The operator is both left-associative and right-associative.
578 /// The operator is left-associative.
580 /// The operator is not associative.
582 /// The operator is right-associative.
586 /// Returns the associativity/fixity of an operator. The difference with
587 /// `AssocOp::fixity` is that an operator can be both left and right associative
588 /// (such as `+`: `a + b + c == (a + b) + c == a + (b + c)`.
590 /// Chained `as` and explicit `:` type coercion never need inner parenthesis so
591 /// they are considered
594 fn associativity(op: AssocOp) -> Associativity {
595 use rustc_ast::util::parser::AssocOp::{
596 Add, As, Assign, AssignOp, BitAnd, BitOr, BitXor, Colon, Divide, DotDot, DotDotEq, Equal, Greater,
597 GreaterEqual, LAnd, LOr, Less, LessEqual, Modulus, Multiply, NotEqual, ShiftLeft, ShiftRight, Subtract,
601 Assign | AssignOp(_) => Associativity::Right,
602 Add | BitAnd | BitOr | BitXor | LAnd | LOr | Multiply | As | Colon => Associativity::Both,
603 Divide | Equal | Greater | GreaterEqual | Less | LessEqual | Modulus | NotEqual | ShiftLeft | ShiftRight
604 | Subtract => Associativity::Left,
605 DotDot | DotDotEq => Associativity::None,
609 /// Converts a `hir::BinOp` to the corresponding assigning binary operator.
610 fn hirbinop2assignop(op: hir::BinOp) -> AssocOp {
611 use rustc_ast::token::BinOpToken::{And, Caret, Minus, Or, Percent, Plus, Shl, Shr, Slash, Star};
613 AssocOp::AssignOp(match op.node {
614 hir::BinOpKind::Add => Plus,
615 hir::BinOpKind::BitAnd => And,
616 hir::BinOpKind::BitOr => Or,
617 hir::BinOpKind::BitXor => Caret,
618 hir::BinOpKind::Div => Slash,
619 hir::BinOpKind::Mul => Star,
620 hir::BinOpKind::Rem => Percent,
621 hir::BinOpKind::Shl => Shl,
622 hir::BinOpKind::Shr => Shr,
623 hir::BinOpKind::Sub => Minus,
632 | hir::BinOpKind::Or => panic!("This operator does not exist"),
636 /// Converts an `ast::BinOp` to the corresponding assigning binary operator.
637 fn astbinop2assignop(op: ast::BinOp) -> AssocOp {
638 use rustc_ast::ast::BinOpKind::{
639 Add, And, BitAnd, BitOr, BitXor, Div, Eq, Ge, Gt, Le, Lt, Mul, Ne, Or, Rem, Shl, Shr, Sub,
641 use rustc_ast::token::BinOpToken;
643 AssocOp::AssignOp(match op.node {
644 Add => BinOpToken::Plus,
645 BitAnd => BinOpToken::And,
646 BitOr => BinOpToken::Or,
647 BitXor => BinOpToken::Caret,
648 Div => BinOpToken::Slash,
649 Mul => BinOpToken::Star,
650 Rem => BinOpToken::Percent,
651 Shl => BinOpToken::Shl,
652 Shr => BinOpToken::Shr,
653 Sub => BinOpToken::Minus,
654 And | Eq | Ge | Gt | Le | Lt | Ne | Or => panic!("This operator does not exist"),
658 /// Returns the indentation before `span` if there are nothing but `[ \t]`
659 /// before it on its line.
660 fn indentation<T: LintContext>(cx: &T, span: Span) -> Option<String> {
661 let lo = cx.sess().source_map().lookup_char_pos(span.lo());
663 .get_line(lo.line - 1 /* line numbers in `Loc` are 1-based */)
665 if let Some((pos, _)) = line.char_indices().find(|&(_, c)| c != ' ' && c != '\t') {
666 // We can mix char and byte positions here because we only consider `[ \t]`.
667 if lo.col == CharPos(pos) {
668 Some(line[..pos].into())
678 /// Convenience extension trait for `DiagnosticBuilder`.
679 pub trait DiagnosticBuilderExt<T: LintContext> {
680 /// Suggests to add an attribute to an item.
682 /// Correctly handles indentation of the attribute and item.
687 /// diag.suggest_item_with_attr(cx, item, "#[derive(Default)]");
689 fn suggest_item_with_attr<D: Display + ?Sized>(
695 applicability: Applicability,
698 /// Suggest to add an item before another.
700 /// The item should not be indented (except for inner indentation).
705 /// diag.suggest_prepend_item(cx, item,
710 fn suggest_prepend_item(&mut self, cx: &T, item: Span, msg: &str, new_item: &str, applicability: Applicability);
712 /// Suggest to completely remove an item.
714 /// This will remove an item and all following whitespace until the next non-whitespace
715 /// character. This should work correctly if item is on the same indentation level as the
721 /// diag.suggest_remove_item(cx, item, "remove this")
723 fn suggest_remove_item(&mut self, cx: &T, item: Span, msg: &str, applicability: Applicability);
726 impl<T: LintContext> DiagnosticBuilderExt<T> for rustc_errors::DiagnosticBuilder<'_> {
727 fn suggest_item_with_attr<D: Display + ?Sized>(
733 applicability: Applicability,
735 if let Some(indent) = indentation(cx, item) {
736 let span = item.with_hi(item.lo());
738 self.span_suggestion(span, msg, format!("{}\n{}", attr, indent), applicability);
742 fn suggest_prepend_item(&mut self, cx: &T, item: Span, msg: &str, new_item: &str, applicability: Applicability) {
743 if let Some(indent) = indentation(cx, item) {
744 let span = item.with_hi(item.lo());
746 let mut first = true;
747 let new_item = new_item
754 format!("{}{}\n", indent, l)
757 .collect::<String>();
759 self.span_suggestion(span, msg, format!("{}\n{}", new_item, indent), applicability);
763 fn suggest_remove_item(&mut self, cx: &T, item: Span, msg: &str, applicability: Applicability) {
764 let mut remove_span = item;
765 let hi = cx.sess().source_map().next_point(remove_span).hi();
766 let fmpos = cx.sess().source_map().lookup_byte_offset(hi);
768 if let Some(ref src) = fmpos.sf.src {
769 let non_whitespace_offset = src[fmpos.pos.to_usize()..].find(|c| c != ' ' && c != '\t' && c != '\n');
771 if let Some(non_whitespace_offset) = non_whitespace_offset {
772 remove_span = remove_span
773 .with_hi(remove_span.hi() + BytePos(non_whitespace_offset.try_into().expect("offset too large")));
777 self.span_suggestion(remove_span, msg, String::new(), applicability);
781 /// Suggestion results for handling closure
782 /// args dereferencing and borrowing
783 pub struct DerefClosure {
784 /// confidence on the built suggestion
785 pub applicability: Applicability,
786 /// gradually built suggestion
787 pub suggestion: String,
790 /// Build suggestion gradually by handling closure arg specific usages,
791 /// such as explicit deref and borrowing cases.
792 /// Returns `None` if no such use cases have been triggered in closure body
794 /// note: this only works on single line immutable closures with exactly one input parameter.
795 pub fn deref_closure_args<'tcx>(cx: &LateContext<'_>, closure: &'tcx hir::Expr<'_>) -> Option<DerefClosure> {
796 if let hir::ExprKind::Closure(_, fn_decl, body_id, ..) = closure.kind {
797 let closure_body = cx.tcx.hir().body(body_id);
798 // is closure arg a type annotated double reference (i.e.: `|x: &&i32| ...`)
799 // a type annotation is present if param `kind` is different from `TyKind::Infer`
800 let closure_arg_is_type_annotated_double_ref = if let TyKind::Rptr(_, MutTy { ty, .. }) = fn_decl.inputs[0].kind
802 matches!(ty.kind, TyKind::Rptr(_, MutTy { .. }))
807 let mut visitor = DerefDelegate {
809 closure_span: closure.span,
810 closure_arg_is_type_annotated_double_ref,
811 next_pos: closure.span.lo(),
812 suggestion_start: String::new(),
813 applicability: Applicability::MaybeIncorrect,
816 let fn_def_id = cx.tcx.hir().local_def_id(closure.hir_id);
817 cx.tcx.infer_ctxt().enter(|infcx| {
818 ExprUseVisitor::new(&mut visitor, &infcx, fn_def_id, cx.param_env, cx.typeck_results())
819 .consume_body(closure_body);
822 if !visitor.suggestion_start.is_empty() {
823 return Some(DerefClosure {
824 applicability: visitor.applicability,
825 suggestion: visitor.finish(),
832 /// Visitor struct used for tracking down
833 /// dereferencing and borrowing of closure's args
834 struct DerefDelegate<'a, 'tcx> {
835 /// The late context of the lint
836 cx: &'a LateContext<'tcx>,
837 /// The span of the input closure to adapt
839 /// Indicates if the arg of the closure is a type annotated double reference
840 closure_arg_is_type_annotated_double_ref: bool,
841 /// last position of the span to gradually build the suggestion
843 /// starting part of the gradually built suggestion
844 suggestion_start: String,
845 /// confidence on the built suggestion
846 applicability: Applicability,
849 impl<'tcx> DerefDelegate<'_, 'tcx> {
850 /// build final suggestion:
851 /// - create the ending part of suggestion
852 /// - concatenate starting and ending parts
853 /// - potentially remove needless borrowing
854 pub fn finish(&mut self) -> String {
855 let end_span = Span::new(self.next_pos, self.closure_span.hi(), self.closure_span.ctxt(), None);
856 let end_snip = snippet_with_applicability(self.cx, end_span, "..", &mut self.applicability);
857 let sugg = format!("{}{}", self.suggestion_start, end_snip);
858 if self.closure_arg_is_type_annotated_double_ref {
859 sugg.replacen('&', "", 1)
865 /// indicates whether the function from `parent_expr` takes its args by double reference
866 fn func_takes_arg_by_double_ref(&self, parent_expr: &'tcx hir::Expr<'_>, cmt_hir_id: HirId) -> bool {
867 let (call_args, inputs) = match parent_expr.kind {
868 ExprKind::MethodCall(_, _, call_args, _) => {
869 if let Some(method_did) = self.cx.typeck_results().type_dependent_def_id(parent_expr.hir_id) {
870 (call_args, self.cx.tcx.fn_sig(method_did).skip_binder().inputs())
875 ExprKind::Call(func, call_args) => {
876 let typ = self.cx.typeck_results().expr_ty(func);
877 (call_args, typ.fn_sig(self.cx.tcx).skip_binder().inputs())
882 iter::zip(call_args, inputs)
883 .any(|(arg, ty)| arg.hir_id == cmt_hir_id && matches!(ty.kind(), ty::Ref(_, inner, _) if inner.is_ref()))
887 impl<'tcx> Delegate<'tcx> for DerefDelegate<'_, 'tcx> {
888 fn consume(&mut self, _: &PlaceWithHirId<'tcx>, _: HirId) {}
890 #[allow(clippy::too_many_lines)]
891 fn borrow(&mut self, cmt: &PlaceWithHirId<'tcx>, _: HirId, _: ty::BorrowKind) {
892 if let PlaceBase::Local(id) = cmt.place.base {
893 let map = self.cx.tcx.hir();
894 let span = map.span(cmt.hir_id);
895 let start_span = Span::new(self.next_pos, span.lo(), span.ctxt(), None);
896 let mut start_snip = snippet_with_applicability(self.cx, start_span, "..", &mut self.applicability);
898 // identifier referring to the variable currently triggered (i.e.: `fp`)
899 let ident_str = map.name(id).to_string();
900 // full identifier that includes projection (i.e.: `fp.field`)
901 let ident_str_with_proj = snippet(self.cx, span, "..").to_string();
903 if cmt.place.projections.is_empty() {
904 // handle item without any projection, that needs an explicit borrowing
905 // i.e.: suggest `&x` instead of `x`
906 self.suggestion_start.push_str(&format!("{}&{}", start_snip, ident_str));
908 // cases where a parent `Call` or `MethodCall` is using the item
909 // i.e.: suggest `.contains(&x)` for `.find(|x| [1, 2, 3].contains(x)).is_none()`
911 // Note about method calls:
912 // - compiler automatically dereference references if the target type is a reference (works also for
914 // - `self` arguments in the case of `x.is_something()` are also automatically (de)referenced, and
915 // no projection should be suggested
916 if let Some(parent_expr) = get_parent_expr_for_hir(self.cx, cmt.hir_id) {
917 match &parent_expr.kind {
918 // given expression is the self argument and will be handled completely by the compiler
919 // i.e.: `|x| x.is_something()`
920 ExprKind::MethodCall(_, _, [self_expr, ..], _) if self_expr.hir_id == cmt.hir_id => {
921 self.suggestion_start
922 .push_str(&format!("{}{}", start_snip, ident_str_with_proj));
923 self.next_pos = span.hi();
926 // item is used in a call
927 // i.e.: `Call`: `|x| please(x)` or `MethodCall`: `|x| [1, 2, 3].contains(x)`
928 ExprKind::Call(_, [call_args @ ..]) | ExprKind::MethodCall(_, _, [_, call_args @ ..], _) => {
929 let expr = self.cx.tcx.hir().expect_expr(cmt.hir_id);
930 let arg_ty_kind = self.cx.typeck_results().expr_ty(expr).kind();
932 if matches!(arg_ty_kind, ty::Ref(_, _, Mutability::Not)) {
933 // suggest ampersand if call function is taking args by double reference
934 let takes_arg_by_double_ref =
935 self.func_takes_arg_by_double_ref(parent_expr, cmt.hir_id);
937 // compiler will automatically dereference field or index projection, so no need
938 // to suggest ampersand, but full identifier that includes projection is required
939 let has_field_or_index_projection =
940 cmt.place.projections.iter().any(|proj| {
941 matches!(proj.kind, ProjectionKind::Field(..) | ProjectionKind::Index)
944 // no need to bind again if the function doesn't take arg by double ref
945 // and if the item is already a double ref
946 let ident_sugg = if !call_args.is_empty()
947 && !takes_arg_by_double_ref
948 && (self.closure_arg_is_type_annotated_double_ref || has_field_or_index_projection)
950 let ident = if has_field_or_index_projection {
955 format!("{}{}", start_snip, ident)
957 format!("{}&{}", start_snip, ident_str)
959 self.suggestion_start.push_str(&ident_sugg);
960 self.next_pos = span.hi();
964 self.applicability = Applicability::Unspecified;
970 let mut replacement_str = ident_str;
971 let mut projections_handled = false;
972 cmt.place.projections.iter().enumerate().for_each(|(i, proj)| {
974 // Field projection like `|v| v.foo`
975 // no adjustment needed here, as field projections are handled by the compiler
976 ProjectionKind::Field(..) => match cmt.place.ty_before_projection(i).kind() {
977 ty::Adt(..) | ty::Tuple(_) => {
978 replacement_str = ident_str_with_proj.clone();
979 projections_handled = true;
983 // Index projection like `|x| foo[x]`
984 // the index is dropped so we can't get it to build the suggestion,
985 // so the span is set-up again to get more code, using `span.hi()` (i.e.: `foo[x]`)
986 // instead of `span.lo()` (i.e.: `foo`)
987 ProjectionKind::Index => {
988 let start_span = Span::new(self.next_pos, span.hi(), span.ctxt(), None);
989 start_snip = snippet_with_applicability(self.cx, start_span, "..", &mut self.applicability);
990 replacement_str.clear();
991 projections_handled = true;
993 // note: unable to trigger `Subslice` kind in tests
994 ProjectionKind::Subslice => (),
995 ProjectionKind::Deref => {
996 // Explicit derefs are typically handled later on, but
997 // some items do not need explicit deref, such as array accesses,
998 // so we mark them as already processed
999 // i.e.: don't suggest `*sub[1..4].len()` for `|sub| sub[1..4].len() == 3`
1000 if let ty::Ref(_, inner, _) = cmt.place.ty_before_projection(i).kind() {
1001 if matches!(inner.kind(), ty::Ref(_, innermost, _) if innermost.is_array()) {
1002 projections_handled = true;
1009 // handle `ProjectionKind::Deref` by removing one explicit deref
1010 // if no special case was detected (i.e.: suggest `*x` instead of `**x`)
1011 if !projections_handled {
1012 let last_deref = cmt
1016 .rposition(|proj| proj.kind == ProjectionKind::Deref);
1018 if let Some(pos) = last_deref {
1019 let mut projections = cmt.place.projections.clone();
1020 projections.truncate(pos);
1022 for item in projections {
1023 if item.kind == ProjectionKind::Deref {
1024 replacement_str = format!("*{}", replacement_str);
1030 self.suggestion_start
1031 .push_str(&format!("{}{}", start_snip, replacement_str));
1033 self.next_pos = span.hi();
1037 fn mutate(&mut self, _: &PlaceWithHirId<'tcx>, _: HirId) {}
1039 fn fake_read(&mut self, _: rustc_typeck::expr_use_visitor::Place<'tcx>, _: FakeReadCause, _: HirId) {}
1046 use rustc_ast::util::parser::AssocOp;
1047 use std::borrow::Cow;
1049 const SUGGESTION: Sugg<'static> = Sugg::NonParen(Cow::Borrowed("function_call()"));
1052 fn make_return_transform_sugg_into_a_return_call() {
1053 assert_eq!("return function_call()", SUGGESTION.make_return().to_string());
1057 fn blockify_transforms_sugg_into_a_block() {
1058 assert_eq!("{ function_call() }", SUGGESTION.blockify().to_string());
1062 fn binop_maybe_par() {
1063 let sugg = Sugg::BinOp(AssocOp::Add, "1".into(), "1".into());
1064 assert_eq!("(1 + 1)", sugg.maybe_par().to_string());
1066 let sugg = Sugg::BinOp(AssocOp::Add, "(1 + 1)".into(), "(1 + 1)".into());
1067 assert_eq!("((1 + 1) + (1 + 1))", sugg.maybe_par().to_string());
1071 use AssocOp::{Add, Equal, Greater, GreaterEqual, LAnd, LOr, Less, LessEqual, NotEqual};
1073 fn test_not(op: AssocOp, correct: &str) {
1074 let sugg = Sugg::BinOp(op, "x".into(), "y".into());
1075 assert_eq!((!sugg).to_string(), correct);
1078 // Invert the comparison operator.
1079 test_not(Equal, "x != y");
1080 test_not(NotEqual, "x == y");
1081 test_not(Less, "x >= y");
1082 test_not(LessEqual, "x > y");
1083 test_not(Greater, "x <= y");
1084 test_not(GreaterEqual, "x < y");
1086 // Other operators are inverted like !(..).
1087 test_not(Add, "!(x + y)");
1088 test_not(LAnd, "!(x && y)");
1089 test_not(LOr, "!(x || y)");