1 //! Contains utility functions to generate suggestions.
2 #![deny(clippy::missing_docs_in_private_items)]
5 use crate::source::{snippet, snippet_opt, snippet_with_macro_callsite};
6 use rustc_ast::util::parser::AssocOp;
7 use rustc_ast::{ast, token};
8 use rustc_ast_pretty::pprust::token_kind_to_string;
9 use rustc_errors::Applicability;
11 use rustc_lint::{EarlyContext, LateContext, LintContext};
12 use rustc_span::source_map::{CharPos, Span};
13 use rustc_span::{BytePos, Pos};
15 use std::convert::TryInto;
16 use std::fmt::Display;
17 use std::ops::{Add, Neg, Not, Sub};
19 /// A helper type to build suggestion correctly handling parenthesis.
20 #[derive(Clone, PartialEq)]
22 /// An expression that never needs parenthesis such as `1337` or `[0; 42]`.
23 NonParen(Cow<'a, str>),
24 /// An expression that does not fit in other variants.
25 MaybeParen(Cow<'a, str>),
26 /// A binary operator expression, including `as`-casts and explicit type
28 BinOp(AssocOp, Cow<'a, str>),
31 /// Literal constant `0`, for convenience.
32 pub const ZERO: Sugg<'static> = Sugg::NonParen(Cow::Borrowed("0"));
33 /// Literal constant `1`, for convenience.
34 pub const ONE: Sugg<'static> = Sugg::NonParen(Cow::Borrowed("1"));
35 /// a constant represents an empty string, for convenience.
36 pub const EMPTY: Sugg<'static> = Sugg::NonParen(Cow::Borrowed(""));
38 impl Display for Sugg<'_> {
39 fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
41 Sugg::NonParen(ref s) | Sugg::MaybeParen(ref s) | Sugg::BinOp(_, ref s) => s.fmt(f),
46 #[allow(clippy::wrong_self_convention)] // ok, because of the function `as_ty` method
48 /// Prepare a suggestion from an expression.
49 pub fn hir_opt(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option<Self> {
50 snippet_opt(cx, expr.span).map(|snippet| {
51 let snippet = Cow::Owned(snippet);
52 Self::hir_from_snippet(expr, snippet)
56 /// Convenience function around `hir_opt` for suggestions with a default
58 pub fn hir(cx: &LateContext<'_>, expr: &hir::Expr<'_>, default: &'a str) -> Self {
59 Self::hir_opt(cx, expr).unwrap_or(Sugg::NonParen(Cow::Borrowed(default)))
62 /// Same as `hir`, but it adapts the applicability level by following rules:
64 /// - Applicability level `Unspecified` will never be changed.
65 /// - If the span is inside a macro, change the applicability level to `MaybeIncorrect`.
66 /// - If the default value is used and the applicability level is `MachineApplicable`, change it
69 pub fn hir_with_applicability(
73 applicability: &mut Applicability,
75 if *applicability != Applicability::Unspecified && expr.span.from_expansion() {
76 *applicability = Applicability::MaybeIncorrect;
78 Self::hir_opt(cx, expr).unwrap_or_else(|| {
79 if *applicability == Applicability::MachineApplicable {
80 *applicability = Applicability::HasPlaceholders;
82 Sugg::NonParen(Cow::Borrowed(default))
86 /// Same as `hir`, but will use the pre expansion span if the `expr` was in a macro.
87 pub fn hir_with_macro_callsite(cx: &LateContext<'_>, expr: &hir::Expr<'_>, default: &'a str) -> Self {
88 let snippet = snippet_with_macro_callsite(cx, expr.span, default);
90 Self::hir_from_snippet(expr, snippet)
93 /// Generate a suggestion for an expression with the given snippet. This is used by the `hir_*`
94 /// function variants of `Sugg`, since these use different snippet functions.
95 fn hir_from_snippet(expr: &hir::Expr<'_>, snippet: Cow<'a, str>) -> Self {
96 if let Some(range) = higher::range(expr) {
97 let op = match range.limits {
98 ast::RangeLimits::HalfOpen => AssocOp::DotDot,
99 ast::RangeLimits::Closed => AssocOp::DotDotEq,
101 return Sugg::BinOp(op, snippet);
105 hir::ExprKind::AddrOf(..)
106 | hir::ExprKind::Box(..)
107 | hir::ExprKind::If(..)
108 | hir::ExprKind::Closure(..)
109 | hir::ExprKind::Unary(..)
110 | hir::ExprKind::Match(..) => Sugg::MaybeParen(snippet),
111 hir::ExprKind::Continue(..)
112 | hir::ExprKind::Yield(..)
113 | hir::ExprKind::Array(..)
114 | hir::ExprKind::Block(..)
115 | hir::ExprKind::Break(..)
116 | hir::ExprKind::Call(..)
117 | hir::ExprKind::Field(..)
118 | hir::ExprKind::Index(..)
119 | hir::ExprKind::InlineAsm(..)
120 | hir::ExprKind::LlvmInlineAsm(..)
121 | hir::ExprKind::ConstBlock(..)
122 | hir::ExprKind::Lit(..)
123 | hir::ExprKind::Loop(..)
124 | hir::ExprKind::MethodCall(..)
125 | hir::ExprKind::Path(..)
126 | hir::ExprKind::Repeat(..)
127 | hir::ExprKind::Ret(..)
128 | hir::ExprKind::Struct(..)
129 | hir::ExprKind::Tup(..)
130 | hir::ExprKind::DropTemps(_)
131 | hir::ExprKind::Err => Sugg::NonParen(snippet),
132 hir::ExprKind::Assign(..) => Sugg::BinOp(AssocOp::Assign, snippet),
133 hir::ExprKind::AssignOp(op, ..) => Sugg::BinOp(hirbinop2assignop(op), snippet),
134 hir::ExprKind::Binary(op, ..) => Sugg::BinOp(AssocOp::from_ast_binop(higher::binop(op.node)), snippet),
135 hir::ExprKind::Cast(..) => Sugg::BinOp(AssocOp::As, snippet),
136 hir::ExprKind::Type(..) => Sugg::BinOp(AssocOp::Colon, snippet),
140 /// Prepare a suggestion from an expression.
141 pub fn ast(cx: &EarlyContext<'_>, expr: &ast::Expr, default: &'a str) -> Self {
142 use rustc_ast::ast::RangeLimits;
144 let snippet = if expr.span.from_expansion() {
145 snippet_with_macro_callsite(cx, expr.span, default)
147 snippet(cx, expr.span, default)
151 ast::ExprKind::AddrOf(..)
152 | ast::ExprKind::Box(..)
153 | ast::ExprKind::Closure(..)
154 | ast::ExprKind::If(..)
155 | ast::ExprKind::Let(..)
156 | ast::ExprKind::Unary(..)
157 | ast::ExprKind::Match(..) => Sugg::MaybeParen(snippet),
158 ast::ExprKind::Async(..)
159 | ast::ExprKind::Block(..)
160 | ast::ExprKind::Break(..)
161 | ast::ExprKind::Call(..)
162 | ast::ExprKind::Continue(..)
163 | ast::ExprKind::Yield(..)
164 | ast::ExprKind::Field(..)
165 | ast::ExprKind::ForLoop(..)
166 | ast::ExprKind::Index(..)
167 | ast::ExprKind::InlineAsm(..)
168 | ast::ExprKind::LlvmInlineAsm(..)
169 | ast::ExprKind::ConstBlock(..)
170 | ast::ExprKind::Lit(..)
171 | ast::ExprKind::Loop(..)
172 | ast::ExprKind::MacCall(..)
173 | ast::ExprKind::MethodCall(..)
174 | ast::ExprKind::Paren(..)
175 | ast::ExprKind::Underscore
176 | ast::ExprKind::Path(..)
177 | ast::ExprKind::Repeat(..)
178 | ast::ExprKind::Ret(..)
179 | ast::ExprKind::Struct(..)
180 | ast::ExprKind::Try(..)
181 | ast::ExprKind::TryBlock(..)
182 | ast::ExprKind::Tup(..)
183 | ast::ExprKind::Array(..)
184 | ast::ExprKind::While(..)
185 | ast::ExprKind::Await(..)
186 | ast::ExprKind::Err => Sugg::NonParen(snippet),
187 ast::ExprKind::Range(.., RangeLimits::HalfOpen) => Sugg::BinOp(AssocOp::DotDot, snippet),
188 ast::ExprKind::Range(.., RangeLimits::Closed) => Sugg::BinOp(AssocOp::DotDotEq, snippet),
189 ast::ExprKind::Assign(..) => Sugg::BinOp(AssocOp::Assign, snippet),
190 ast::ExprKind::AssignOp(op, ..) => Sugg::BinOp(astbinop2assignop(op), snippet),
191 ast::ExprKind::Binary(op, ..) => Sugg::BinOp(AssocOp::from_ast_binop(op.node), snippet),
192 ast::ExprKind::Cast(..) => Sugg::BinOp(AssocOp::As, snippet),
193 ast::ExprKind::Type(..) => Sugg::BinOp(AssocOp::Colon, snippet),
197 /// Convenience method to create the `<lhs> && <rhs>` suggestion.
198 pub fn and(self, rhs: &Self) -> Sugg<'static> {
199 make_binop(ast::BinOpKind::And, &self, rhs)
202 /// Convenience method to create the `<lhs> & <rhs>` suggestion.
203 pub fn bit_and(self, rhs: &Self) -> Sugg<'static> {
204 make_binop(ast::BinOpKind::BitAnd, &self, rhs)
207 /// Convenience method to create the `<lhs> as <rhs>` suggestion.
208 pub fn as_ty<R: Display>(self, rhs: R) -> Sugg<'static> {
209 make_assoc(AssocOp::As, &self, &Sugg::NonParen(rhs.to_string().into()))
212 /// Convenience method to create the `&<expr>` suggestion.
213 pub fn addr(self) -> Sugg<'static> {
217 /// Convenience method to create the `&mut <expr>` suggestion.
218 pub fn mut_addr(self) -> Sugg<'static> {
219 make_unop("&mut ", self)
222 /// Convenience method to create the `*<expr>` suggestion.
223 pub fn deref(self) -> Sugg<'static> {
227 /// Convenience method to create the `&*<expr>` suggestion. Currently this
228 /// is needed because `sugg.deref().addr()` produces an unnecessary set of
229 /// parentheses around the deref.
230 pub fn addr_deref(self) -> Sugg<'static> {
231 make_unop("&*", self)
234 /// Convenience method to create the `&mut *<expr>` suggestion. Currently
235 /// this is needed because `sugg.deref().mut_addr()` produces an unnecessary
236 /// set of parentheses around the deref.
237 pub fn mut_addr_deref(self) -> Sugg<'static> {
238 make_unop("&mut *", self)
241 /// Convenience method to transform suggestion into a return call
242 pub fn make_return(self) -> Sugg<'static> {
243 Sugg::NonParen(Cow::Owned(format!("return {}", self)))
246 /// Convenience method to transform suggestion into a block
247 /// where the suggestion is a trailing expression
248 pub fn blockify(self) -> Sugg<'static> {
249 Sugg::NonParen(Cow::Owned(format!("{{ {} }}", self)))
252 /// Convenience method to create the `<lhs>..<rhs>` or `<lhs>...<rhs>`
255 pub fn range(self, end: &Self, limit: ast::RangeLimits) -> Sugg<'static> {
257 ast::RangeLimits::HalfOpen => make_assoc(AssocOp::DotDot, &self, end),
258 ast::RangeLimits::Closed => make_assoc(AssocOp::DotDotEq, &self, end),
262 /// Adds parenthesis to any expression that might need them. Suitable to the
263 /// `self` argument of a method call
264 /// (e.g., to build `bar.foo()` or `(1 + 2).foo()`).
265 pub fn maybe_par(self) -> Self {
267 Sugg::NonParen(..) => self,
268 // `(x)` and `(x).y()` both don't need additional parens.
269 Sugg::MaybeParen(sugg) => {
270 if sugg.starts_with('(') && sugg.ends_with(')') {
271 Sugg::MaybeParen(sugg)
273 Sugg::NonParen(format!("({})", sugg).into())
276 Sugg::BinOp(_, sugg) => Sugg::NonParen(format!("({})", sugg).into()),
281 // Copied from the rust standart library, and then edited
282 macro_rules! forward_binop_impls_to_ref {
283 (impl $imp:ident, $method:ident for $t:ty, type Output = $o:ty) => {
284 impl $imp<$t> for &$t {
287 fn $method(self, other: $t) -> $o {
288 $imp::$method(self, &other)
292 impl $imp<&$t> for $t {
295 fn $method(self, other: &$t) -> $o {
296 $imp::$method(&self, other)
303 fn $method(self, other: $t) -> $o {
304 $imp::$method(&self, &other)
310 impl Add for &Sugg<'_> {
311 type Output = Sugg<'static>;
312 fn add(self, rhs: &Sugg<'_>) -> Sugg<'static> {
313 make_binop(ast::BinOpKind::Add, self, rhs)
317 impl Sub for &Sugg<'_> {
318 type Output = Sugg<'static>;
319 fn sub(self, rhs: &Sugg<'_>) -> Sugg<'static> {
320 make_binop(ast::BinOpKind::Sub, self, rhs)
324 forward_binop_impls_to_ref!(impl Add, add for Sugg<'_>, type Output = Sugg<'static>);
325 forward_binop_impls_to_ref!(impl Sub, sub for Sugg<'_>, type Output = Sugg<'static>);
327 impl Neg for Sugg<'_> {
328 type Output = Sugg<'static>;
329 fn neg(self) -> Sugg<'static> {
334 impl Not for Sugg<'_> {
335 type Output = Sugg<'static>;
336 fn not(self) -> Sugg<'static> {
341 /// Helper type to display either `foo` or `(foo)`.
342 struct ParenHelper<T> {
343 /// `true` if parentheses are needed.
345 /// The main thing to display.
349 impl<T> ParenHelper<T> {
350 /// Builds a `ParenHelper`.
351 fn new(paren: bool, wrapped: T) -> Self {
352 Self { paren, wrapped }
356 impl<T: Display> Display for ParenHelper<T> {
357 fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
359 write!(f, "({})", self.wrapped)
366 /// Builds the string for `<op><expr>` adding parenthesis when necessary.
368 /// For convenience, the operator is taken as a string because all unary
369 /// operators have the same
371 pub fn make_unop(op: &str, expr: Sugg<'_>) -> Sugg<'static> {
372 Sugg::MaybeParen(format!("{}{}", op, expr.maybe_par()).into())
375 /// Builds the string for `<lhs> <op> <rhs>` adding parenthesis when necessary.
377 /// Precedence of shift operator relative to other arithmetic operation is
378 /// often confusing so
379 /// parenthesis will always be added for a mix of these.
380 pub fn make_assoc(op: AssocOp, lhs: &Sugg<'_>, rhs: &Sugg<'_>) -> Sugg<'static> {
381 /// Returns `true` if the operator is a shift operator `<<` or `>>`.
382 fn is_shift(op: AssocOp) -> bool {
383 matches!(op, AssocOp::ShiftLeft | AssocOp::ShiftRight)
386 /// Returns `true` if the operator is a arithmetic operator
387 /// (i.e., `+`, `-`, `*`, `/`, `%`).
388 fn is_arith(op: AssocOp) -> bool {
391 AssocOp::Add | AssocOp::Subtract | AssocOp::Multiply | AssocOp::Divide | AssocOp::Modulus
395 /// Returns `true` if the operator `op` needs parenthesis with the operator
396 /// `other` in the direction `dir`.
397 fn needs_paren(op: AssocOp, other: AssocOp, dir: Associativity) -> bool {
398 other.precedence() < op.precedence()
399 || (other.precedence() == op.precedence()
400 && ((op != other && associativity(op) != dir)
401 || (op == other && associativity(op) != Associativity::Both)))
402 || is_shift(op) && is_arith(other)
403 || is_shift(other) && is_arith(op)
406 let lhs_paren = if let Sugg::BinOp(lop, _) = *lhs {
407 needs_paren(op, lop, Associativity::Left)
412 let rhs_paren = if let Sugg::BinOp(rop, _) = *rhs {
413 needs_paren(op, rop, Associativity::Right)
418 let lhs = ParenHelper::new(lhs_paren, lhs);
419 let rhs = ParenHelper::new(rhs_paren, rhs);
420 let sugg = match op {
428 | AssocOp::GreaterEqual
437 | AssocOp::ShiftRight
438 | AssocOp::Subtract => format!(
441 op.to_ast_binop().expect("Those are AST ops").to_string(),
444 AssocOp::Assign => format!("{} = {}", lhs, rhs),
445 AssocOp::AssignOp(op) => format!("{} {}= {}", lhs, token_kind_to_string(&token::BinOp(op)), rhs),
446 AssocOp::As => format!("{} as {}", lhs, rhs),
447 AssocOp::DotDot => format!("{}..{}", lhs, rhs),
448 AssocOp::DotDotEq => format!("{}..={}", lhs, rhs),
449 AssocOp::Colon => format!("{}: {}", lhs, rhs),
452 Sugg::BinOp(op, sugg.into())
455 /// Convenience wrapper around `make_assoc` and `AssocOp::from_ast_binop`.
456 pub fn make_binop(op: ast::BinOpKind, lhs: &Sugg<'_>, rhs: &Sugg<'_>) -> Sugg<'static> {
457 make_assoc(AssocOp::from_ast_binop(op), lhs, rhs)
460 #[derive(PartialEq, Eq, Clone, Copy)]
461 /// Operator associativity.
463 /// The operator is both left-associative and right-associative.
465 /// The operator is left-associative.
467 /// The operator is not associative.
469 /// The operator is right-associative.
473 /// Returns the associativity/fixity of an operator. The difference with
474 /// `AssocOp::fixity` is that an operator can be both left and right associative
475 /// (such as `+`: `a + b + c == (a + b) + c == a + (b + c)`.
477 /// Chained `as` and explicit `:` type coercion never need inner parenthesis so
478 /// they are considered
481 fn associativity(op: AssocOp) -> Associativity {
482 use rustc_ast::util::parser::AssocOp::{
483 Add, As, Assign, AssignOp, BitAnd, BitOr, BitXor, Colon, Divide, DotDot, DotDotEq, Equal, Greater,
484 GreaterEqual, LAnd, LOr, Less, LessEqual, Modulus, Multiply, NotEqual, ShiftLeft, ShiftRight, Subtract,
488 Assign | AssignOp(_) => Associativity::Right,
489 Add | BitAnd | BitOr | BitXor | LAnd | LOr | Multiply | As | Colon => Associativity::Both,
490 Divide | Equal | Greater | GreaterEqual | Less | LessEqual | Modulus | NotEqual | ShiftLeft | ShiftRight
491 | Subtract => Associativity::Left,
492 DotDot | DotDotEq => Associativity::None,
496 /// Converts a `hir::BinOp` to the corresponding assigning binary operator.
497 fn hirbinop2assignop(op: hir::BinOp) -> AssocOp {
498 use rustc_ast::token::BinOpToken::{And, Caret, Minus, Or, Percent, Plus, Shl, Shr, Slash, Star};
500 AssocOp::AssignOp(match op.node {
501 hir::BinOpKind::Add => Plus,
502 hir::BinOpKind::BitAnd => And,
503 hir::BinOpKind::BitOr => Or,
504 hir::BinOpKind::BitXor => Caret,
505 hir::BinOpKind::Div => Slash,
506 hir::BinOpKind::Mul => Star,
507 hir::BinOpKind::Rem => Percent,
508 hir::BinOpKind::Shl => Shl,
509 hir::BinOpKind::Shr => Shr,
510 hir::BinOpKind::Sub => Minus,
519 | hir::BinOpKind::Or => panic!("This operator does not exist"),
523 /// Converts an `ast::BinOp` to the corresponding assigning binary operator.
524 fn astbinop2assignop(op: ast::BinOp) -> AssocOp {
525 use rustc_ast::ast::BinOpKind::{
526 Add, And, BitAnd, BitOr, BitXor, Div, Eq, Ge, Gt, Le, Lt, Mul, Ne, Or, Rem, Shl, Shr, Sub,
528 use rustc_ast::token::BinOpToken;
530 AssocOp::AssignOp(match op.node {
531 Add => BinOpToken::Plus,
532 BitAnd => BinOpToken::And,
533 BitOr => BinOpToken::Or,
534 BitXor => BinOpToken::Caret,
535 Div => BinOpToken::Slash,
536 Mul => BinOpToken::Star,
537 Rem => BinOpToken::Percent,
538 Shl => BinOpToken::Shl,
539 Shr => BinOpToken::Shr,
540 Sub => BinOpToken::Minus,
541 And | Eq | Ge | Gt | Le | Lt | Ne | Or => panic!("This operator does not exist"),
545 /// Returns the indentation before `span` if there are nothing but `[ \t]`
546 /// before it on its line.
547 fn indentation<T: LintContext>(cx: &T, span: Span) -> Option<String> {
548 let lo = cx.sess().source_map().lookup_char_pos(span.lo());
550 .get_line(lo.line - 1 /* line numbers in `Loc` are 1-based */)
552 if let Some((pos, _)) = line.char_indices().find(|&(_, c)| c != ' ' && c != '\t') {
553 // We can mix char and byte positions here because we only consider `[ \t]`.
554 if lo.col == CharPos(pos) {
555 Some(line[..pos].into())
565 /// Convenience extension trait for `DiagnosticBuilder`.
566 pub trait DiagnosticBuilderExt<T: LintContext> {
567 /// Suggests to add an attribute to an item.
569 /// Correctly handles indentation of the attribute and item.
574 /// diag.suggest_item_with_attr(cx, item, "#[derive(Default)]");
576 fn suggest_item_with_attr<D: Display + ?Sized>(
582 applicability: Applicability,
585 /// Suggest to add an item before another.
587 /// The item should not be indented (except for inner indentation).
592 /// diag.suggest_prepend_item(cx, item,
597 fn suggest_prepend_item(&mut self, cx: &T, item: Span, msg: &str, new_item: &str, applicability: Applicability);
599 /// Suggest to completely remove an item.
601 /// This will remove an item and all following whitespace until the next non-whitespace
602 /// character. This should work correctly if item is on the same indentation level as the
608 /// diag.suggest_remove_item(cx, item, "remove this")
610 fn suggest_remove_item(&mut self, cx: &T, item: Span, msg: &str, applicability: Applicability);
613 impl<T: LintContext> DiagnosticBuilderExt<T> for rustc_errors::DiagnosticBuilder<'_> {
614 fn suggest_item_with_attr<D: Display + ?Sized>(
620 applicability: Applicability,
622 if let Some(indent) = indentation(cx, item) {
623 let span = item.with_hi(item.lo());
625 self.span_suggestion(span, msg, format!("{}\n{}", attr, indent), applicability);
629 fn suggest_prepend_item(&mut self, cx: &T, item: Span, msg: &str, new_item: &str, applicability: Applicability) {
630 if let Some(indent) = indentation(cx, item) {
631 let span = item.with_hi(item.lo());
633 let mut first = true;
634 let new_item = new_item
641 format!("{}{}\n", indent, l)
644 .collect::<String>();
646 self.span_suggestion(span, msg, format!("{}\n{}", new_item, indent), applicability);
650 fn suggest_remove_item(&mut self, cx: &T, item: Span, msg: &str, applicability: Applicability) {
651 let mut remove_span = item;
652 let hi = cx.sess().source_map().next_point(remove_span).hi();
653 let fmpos = cx.sess().source_map().lookup_byte_offset(hi);
655 if let Some(ref src) = fmpos.sf.src {
656 let non_whitespace_offset = src[fmpos.pos.to_usize()..].find(|c| c != ' ' && c != '\t' && c != '\n');
658 if let Some(non_whitespace_offset) = non_whitespace_offset {
659 remove_span = remove_span
660 .with_hi(remove_span.hi() + BytePos(non_whitespace_offset.try_into().expect("offset too large")))
664 self.span_suggestion(remove_span, msg, String::new(), applicability);
671 use std::borrow::Cow;
673 const SUGGESTION: Sugg<'static> = Sugg::NonParen(Cow::Borrowed("function_call()"));
676 fn make_return_transform_sugg_into_a_return_call() {
677 assert_eq!("return function_call()", SUGGESTION.make_return().to_string());
681 fn blockify_transforms_sugg_into_a_block() {
682 assert_eq!("{ function_call() }", SUGGESTION.blockify().to_string());