1 //! Contains utility functions to generate suggestions.
2 #![deny(clippy::missing_docs_in_private_items)]
4 use crate::utils::{higher, 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;
18 /// A helper type to build suggestion correctly handling parenthesis.
20 /// An expression that never needs parenthesis such as `1337` or `[0; 42]`.
21 NonParen(Cow<'a, str>),
22 /// An expression that does not fit in other variants.
23 MaybeParen(Cow<'a, str>),
24 /// A binary operator expression, including `as`-casts and explicit type
26 BinOp(AssocOp, Cow<'a, str>),
29 /// Literal constant `1`, for convenience.
30 pub const ONE: Sugg<'static> = Sugg::NonParen(Cow::Borrowed("1"));
32 impl Display for Sugg<'_> {
33 fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
35 Sugg::NonParen(ref s) | Sugg::MaybeParen(ref s) | Sugg::BinOp(_, ref s) => s.fmt(f),
40 #[allow(clippy::wrong_self_convention)] // ok, because of the function `as_ty` method
42 /// Prepare a suggestion from an expression.
43 pub fn hir_opt(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>) -> Option<Self> {
44 snippet_opt(cx, expr.span).map(|snippet| {
45 let snippet = Cow::Owned(snippet);
46 Self::hir_from_snippet(cx, expr, snippet)
50 /// Convenience function around `hir_opt` for suggestions with a default
52 pub fn hir(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, default: &'a str) -> Self {
53 Self::hir_opt(cx, expr).unwrap_or_else(|| Sugg::NonParen(Cow::Borrowed(default)))
56 /// Same as `hir`, but it adapts the applicability level by following rules:
58 /// - Applicability level `Unspecified` will never be changed.
59 /// - If the span is inside a macro, change the applicability level to `MaybeIncorrect`.
60 /// - If the default value is used and the applicability level is `MachineApplicable`, change it
63 pub fn hir_with_applicability(
64 cx: &LateContext<'_, '_>,
67 applicability: &mut Applicability,
69 if *applicability != Applicability::Unspecified && expr.span.from_expansion() {
70 *applicability = Applicability::MaybeIncorrect;
72 Self::hir_opt(cx, expr).unwrap_or_else(|| {
73 if *applicability == Applicability::MachineApplicable {
74 *applicability = Applicability::HasPlaceholders;
76 Sugg::NonParen(Cow::Borrowed(default))
80 /// Same as `hir`, but will use the pre expansion span if the `expr` was in a macro.
81 pub fn hir_with_macro_callsite(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, default: &'a str) -> Self {
82 let snippet = snippet_with_macro_callsite(cx, expr.span, default);
84 Self::hir_from_snippet(cx, expr, snippet)
87 /// Generate a suggestion for an expression with the given snippet. This is used by the `hir_*`
88 /// function variants of `Sugg`, since these use different snippet functions.
89 fn hir_from_snippet(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, snippet: Cow<'a, str>) -> Self {
90 if let Some(range) = higher::range(cx, expr) {
91 let op = match range.limits {
92 ast::RangeLimits::HalfOpen => AssocOp::DotDot,
93 ast::RangeLimits::Closed => AssocOp::DotDotEq,
95 return Sugg::BinOp(op, snippet);
99 hir::ExprKind::AddrOf(..)
100 | hir::ExprKind::Box(..)
101 | hir::ExprKind::Closure(..)
102 | hir::ExprKind::Unary(..)
103 | hir::ExprKind::Match(..) => Sugg::MaybeParen(snippet),
104 hir::ExprKind::Continue(..)
105 | hir::ExprKind::Yield(..)
106 | hir::ExprKind::Array(..)
107 | hir::ExprKind::Block(..)
108 | hir::ExprKind::Break(..)
109 | hir::ExprKind::Call(..)
110 | hir::ExprKind::Field(..)
111 | hir::ExprKind::Index(..)
112 | hir::ExprKind::InlineAsm(..)
113 | hir::ExprKind::Lit(..)
114 | hir::ExprKind::Loop(..)
115 | hir::ExprKind::MethodCall(..)
116 | hir::ExprKind::Path(..)
117 | hir::ExprKind::Repeat(..)
118 | hir::ExprKind::Ret(..)
119 | hir::ExprKind::Struct(..)
120 | hir::ExprKind::Tup(..)
121 | hir::ExprKind::DropTemps(_)
122 | hir::ExprKind::Err => Sugg::NonParen(snippet),
123 hir::ExprKind::Assign(..) => Sugg::BinOp(AssocOp::Assign, snippet),
124 hir::ExprKind::AssignOp(op, ..) => Sugg::BinOp(hirbinop2assignop(op), snippet),
125 hir::ExprKind::Binary(op, ..) => Sugg::BinOp(AssocOp::from_ast_binop(higher::binop(op.node)), snippet),
126 hir::ExprKind::Cast(..) => Sugg::BinOp(AssocOp::As, snippet),
127 hir::ExprKind::Type(..) => Sugg::BinOp(AssocOp::Colon, snippet),
131 /// Prepare a suggestion from an expression.
132 pub fn ast(cx: &EarlyContext<'_>, expr: &ast::Expr, default: &'a str) -> Self {
133 use rustc_ast::ast::RangeLimits;
135 let snippet = snippet(cx, expr.span, default);
138 ast::ExprKind::AddrOf(..)
139 | ast::ExprKind::Box(..)
140 | ast::ExprKind::Closure(..)
141 | ast::ExprKind::If(..)
142 | ast::ExprKind::Let(..)
143 | ast::ExprKind::Unary(..)
144 | ast::ExprKind::Match(..) => Sugg::MaybeParen(snippet),
145 ast::ExprKind::Async(..)
146 | ast::ExprKind::Block(..)
147 | ast::ExprKind::Break(..)
148 | ast::ExprKind::Call(..)
149 | ast::ExprKind::Continue(..)
150 | ast::ExprKind::Yield(..)
151 | ast::ExprKind::Field(..)
152 | ast::ExprKind::ForLoop(..)
153 | ast::ExprKind::Index(..)
154 | ast::ExprKind::InlineAsm(..)
155 | ast::ExprKind::Lit(..)
156 | ast::ExprKind::Loop(..)
157 | ast::ExprKind::Mac(..)
158 | ast::ExprKind::MethodCall(..)
159 | ast::ExprKind::Paren(..)
160 | ast::ExprKind::Path(..)
161 | ast::ExprKind::Repeat(..)
162 | ast::ExprKind::Ret(..)
163 | ast::ExprKind::Struct(..)
164 | ast::ExprKind::Try(..)
165 | ast::ExprKind::TryBlock(..)
166 | ast::ExprKind::Tup(..)
167 | ast::ExprKind::Array(..)
168 | ast::ExprKind::While(..)
169 | ast::ExprKind::Await(..)
170 | ast::ExprKind::Err => Sugg::NonParen(snippet),
171 ast::ExprKind::Range(.., RangeLimits::HalfOpen) => Sugg::BinOp(AssocOp::DotDot, snippet),
172 ast::ExprKind::Range(.., RangeLimits::Closed) => Sugg::BinOp(AssocOp::DotDotEq, snippet),
173 ast::ExprKind::Assign(..) => Sugg::BinOp(AssocOp::Assign, snippet),
174 ast::ExprKind::AssignOp(op, ..) => Sugg::BinOp(astbinop2assignop(op), snippet),
175 ast::ExprKind::Binary(op, ..) => Sugg::BinOp(AssocOp::from_ast_binop(op.node), snippet),
176 ast::ExprKind::Cast(..) => Sugg::BinOp(AssocOp::As, snippet),
177 ast::ExprKind::Type(..) => Sugg::BinOp(AssocOp::Colon, snippet),
181 /// Convenience method to create the `<lhs> && <rhs>` suggestion.
182 pub fn and(self, rhs: &Self) -> Sugg<'static> {
183 make_binop(ast::BinOpKind::And, &self, rhs)
186 /// Convenience method to create the `<lhs> & <rhs>` suggestion.
187 pub fn bit_and(self, rhs: &Self) -> Sugg<'static> {
188 make_binop(ast::BinOpKind::BitAnd, &self, rhs)
191 /// Convenience method to create the `<lhs> as <rhs>` suggestion.
192 pub fn as_ty<R: Display>(self, rhs: R) -> Sugg<'static> {
193 make_assoc(AssocOp::As, &self, &Sugg::NonParen(rhs.to_string().into()))
196 /// Convenience method to create the `&<expr>` suggestion.
197 pub fn addr(self) -> Sugg<'static> {
201 /// Convenience method to create the `&mut <expr>` suggestion.
202 pub fn mut_addr(self) -> Sugg<'static> {
203 make_unop("&mut ", self)
206 /// Convenience method to create the `*<expr>` suggestion.
207 pub fn deref(self) -> Sugg<'static> {
211 /// Convenience method to create the `&*<expr>` suggestion. Currently this
212 /// is needed because `sugg.deref().addr()` produces an unnecessary set of
213 /// parentheses around the deref.
214 pub fn addr_deref(self) -> Sugg<'static> {
215 make_unop("&*", self)
218 /// Convenience method to create the `&mut *<expr>` suggestion. Currently
219 /// this is needed because `sugg.deref().mut_addr()` produces an unnecessary
220 /// set of parentheses around the deref.
221 pub fn mut_addr_deref(self) -> Sugg<'static> {
222 make_unop("&mut *", self)
225 /// Convenience method to transform suggestion into a return call
226 pub fn make_return(self) -> Sugg<'static> {
227 Sugg::NonParen(Cow::Owned(format!("return {}", self)))
230 /// Convenience method to transform suggestion into a block
231 /// where the suggestion is a trailing expression
232 pub fn blockify(self) -> Sugg<'static> {
233 Sugg::NonParen(Cow::Owned(format!("{{ {} }}", self)))
236 /// Convenience method to create the `<lhs>..<rhs>` or `<lhs>...<rhs>`
239 pub fn range(self, end: &Self, limit: ast::RangeLimits) -> Sugg<'static> {
241 ast::RangeLimits::HalfOpen => make_assoc(AssocOp::DotDot, &self, end),
242 ast::RangeLimits::Closed => make_assoc(AssocOp::DotDotEq, &self, end),
246 /// Adds parenthesis to any expression that might need them. Suitable to the
247 /// `self` argument of a method call
248 /// (e.g., to build `bar.foo()` or `(1 + 2).foo()`).
249 pub fn maybe_par(self) -> Self {
251 Sugg::NonParen(..) => self,
252 // `(x)` and `(x).y()` both don't need additional parens.
253 Sugg::MaybeParen(sugg) => {
254 if sugg.starts_with('(') && sugg.ends_with(')') {
255 Sugg::MaybeParen(sugg)
257 Sugg::NonParen(format!("({})", sugg).into())
260 Sugg::BinOp(_, sugg) => Sugg::NonParen(format!("({})", sugg).into()),
265 impl<'a, 'b> std::ops::Add<Sugg<'b>> for Sugg<'a> {
266 type Output = Sugg<'static>;
267 fn add(self, rhs: Sugg<'b>) -> Sugg<'static> {
268 make_binop(ast::BinOpKind::Add, &self, &rhs)
272 impl<'a, 'b> std::ops::Sub<Sugg<'b>> for Sugg<'a> {
273 type Output = Sugg<'static>;
274 fn sub(self, rhs: Sugg<'b>) -> Sugg<'static> {
275 make_binop(ast::BinOpKind::Sub, &self, &rhs)
279 impl<'a> std::ops::Not for Sugg<'a> {
280 type Output = Sugg<'static>;
281 fn not(self) -> Sugg<'static> {
286 /// Helper type to display either `foo` or `(foo)`.
287 struct ParenHelper<T> {
288 /// `true` if parentheses are needed.
290 /// The main thing to display.
294 impl<T> ParenHelper<T> {
295 /// Builds a `ParenHelper`.
296 fn new(paren: bool, wrapped: T) -> Self {
297 Self { paren, wrapped }
301 impl<T: Display> Display for ParenHelper<T> {
302 fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
304 write!(f, "({})", self.wrapped)
311 /// Builds the string for `<op><expr>` adding parenthesis when necessary.
313 /// For convenience, the operator is taken as a string because all unary
314 /// operators have the same
316 pub fn make_unop(op: &str, expr: Sugg<'_>) -> Sugg<'static> {
317 Sugg::MaybeParen(format!("{}{}", op, expr.maybe_par()).into())
320 /// Builds the string for `<lhs> <op> <rhs>` adding parenthesis when necessary.
322 /// Precedence of shift operator relative to other arithmetic operation is
323 /// often confusing so
324 /// parenthesis will always be added for a mix of these.
325 pub fn make_assoc(op: AssocOp, lhs: &Sugg<'_>, rhs: &Sugg<'_>) -> Sugg<'static> {
326 /// Returns `true` if the operator is a shift operator `<<` or `>>`.
327 fn is_shift(op: &AssocOp) -> bool {
328 matches!(*op, AssocOp::ShiftLeft | AssocOp::ShiftRight)
331 /// Returns `true` if the operator is a arithmetic operator
332 /// (i.e., `+`, `-`, `*`, `/`, `%`).
333 fn is_arith(op: &AssocOp) -> bool {
336 AssocOp::Add | AssocOp::Subtract | AssocOp::Multiply | AssocOp::Divide | AssocOp::Modulus
340 /// Returns `true` if the operator `op` needs parenthesis with the operator
341 /// `other` in the direction `dir`.
342 fn needs_paren(op: &AssocOp, other: &AssocOp, dir: Associativity) -> bool {
343 other.precedence() < op.precedence()
344 || (other.precedence() == op.precedence()
345 && ((op != other && associativity(op) != dir)
346 || (op == other && associativity(op) != Associativity::Both)))
347 || is_shift(op) && is_arith(other)
348 || is_shift(other) && is_arith(op)
351 let lhs_paren = if let Sugg::BinOp(ref lop, _) = *lhs {
352 needs_paren(&op, lop, Associativity::Left)
357 let rhs_paren = if let Sugg::BinOp(ref rop, _) = *rhs {
358 needs_paren(&op, rop, Associativity::Right)
363 let lhs = ParenHelper::new(lhs_paren, lhs);
364 let rhs = ParenHelper::new(rhs_paren, rhs);
365 let sugg = match op {
373 | AssocOp::GreaterEqual
382 | AssocOp::ShiftRight
383 | AssocOp::Subtract => format!(
386 op.to_ast_binop().expect("Those are AST ops").to_string(),
389 AssocOp::Assign => format!("{} = {}", lhs, rhs),
390 AssocOp::AssignOp(op) => format!("{} {}= {}", lhs, token_kind_to_string(&token::BinOp(op)), rhs),
391 AssocOp::As => format!("{} as {}", lhs, rhs),
392 AssocOp::DotDot => format!("{}..{}", lhs, rhs),
393 AssocOp::DotDotEq => format!("{}..={}", lhs, rhs),
394 AssocOp::Colon => format!("{}: {}", lhs, rhs),
397 Sugg::BinOp(op, sugg.into())
400 /// Convenience wrapper around `make_assoc` and `AssocOp::from_ast_binop`.
401 pub fn make_binop(op: ast::BinOpKind, lhs: &Sugg<'_>, rhs: &Sugg<'_>) -> Sugg<'static> {
402 make_assoc(AssocOp::from_ast_binop(op), lhs, rhs)
405 #[derive(PartialEq, Eq, Clone, Copy)]
406 /// Operator associativity.
408 /// The operator is both left-associative and right-associative.
410 /// The operator is left-associative.
412 /// The operator is not associative.
414 /// The operator is right-associative.
418 /// Returns the associativity/fixity of an operator. The difference with
419 /// `AssocOp::fixity` is that an operator can be both left and right associative
420 /// (such as `+`: `a + b + c == (a + b) + c == a + (b + c)`.
422 /// Chained `as` and explicit `:` type coercion never need inner parenthesis so
423 /// they are considered
426 fn associativity(op: &AssocOp) -> Associativity {
427 use rustc_ast::util::parser::AssocOp::{
428 Add, As, Assign, AssignOp, BitAnd, BitOr, BitXor, Colon, Divide, DotDot, DotDotEq, Equal, Greater,
429 GreaterEqual, LAnd, LOr, Less, LessEqual, Modulus, Multiply, NotEqual, ShiftLeft, ShiftRight, Subtract,
433 Assign | AssignOp(_) => Associativity::Right,
434 Add | BitAnd | BitOr | BitXor | LAnd | LOr | Multiply | As | Colon => Associativity::Both,
435 Divide | Equal | Greater | GreaterEqual | Less | LessEqual | Modulus | NotEqual | ShiftLeft | ShiftRight
436 | Subtract => Associativity::Left,
437 DotDot | DotDotEq => Associativity::None,
441 /// Converts a `hir::BinOp` to the corresponding assigning binary operator.
442 fn hirbinop2assignop(op: hir::BinOp) -> AssocOp {
443 use rustc_ast::token::BinOpToken::{And, Caret, Minus, Or, Percent, Plus, Shl, Shr, Slash, Star};
445 AssocOp::AssignOp(match op.node {
446 hir::BinOpKind::Add => Plus,
447 hir::BinOpKind::BitAnd => And,
448 hir::BinOpKind::BitOr => Or,
449 hir::BinOpKind::BitXor => Caret,
450 hir::BinOpKind::Div => Slash,
451 hir::BinOpKind::Mul => Star,
452 hir::BinOpKind::Rem => Percent,
453 hir::BinOpKind::Shl => Shl,
454 hir::BinOpKind::Shr => Shr,
455 hir::BinOpKind::Sub => Minus,
464 | hir::BinOpKind::Or => panic!("This operator does not exist"),
468 /// Converts an `ast::BinOp` to the corresponding assigning binary operator.
469 fn astbinop2assignop(op: ast::BinOp) -> AssocOp {
470 use rustc_ast::ast::BinOpKind::{
471 Add, And, BitAnd, BitOr, BitXor, Div, Eq, Ge, Gt, Le, Lt, Mul, Ne, Or, Rem, Shl, Shr, Sub,
473 use rustc_ast::token::BinOpToken;
475 AssocOp::AssignOp(match op.node {
476 Add => BinOpToken::Plus,
477 BitAnd => BinOpToken::And,
478 BitOr => BinOpToken::Or,
479 BitXor => BinOpToken::Caret,
480 Div => BinOpToken::Slash,
481 Mul => BinOpToken::Star,
482 Rem => BinOpToken::Percent,
483 Shl => BinOpToken::Shl,
484 Shr => BinOpToken::Shr,
485 Sub => BinOpToken::Minus,
486 And | Eq | Ge | Gt | Le | Lt | Ne | Or => panic!("This operator does not exist"),
490 /// Returns the indentation before `span` if there are nothing but `[ \t]`
491 /// before it on its line.
492 fn indentation<T: LintContext>(cx: &T, span: Span) -> Option<String> {
493 let lo = cx.sess().source_map().lookup_char_pos(span.lo());
494 if let Some(line) = lo.file.get_line(lo.line - 1 /* line numbers in `Loc` are 1-based */) {
495 if let Some((pos, _)) = line.char_indices().find(|&(_, c)| c != ' ' && c != '\t') {
496 // We can mix char and byte positions here because we only consider `[ \t]`.
497 if lo.col == CharPos(pos) {
498 Some(line[..pos].into())
510 /// Convenience extension trait for `DiagnosticBuilder`.
511 pub trait DiagnosticBuilderExt<'a, T: LintContext> {
512 /// Suggests to add an attribute to an item.
514 /// Correctly handles indentation of the attribute and item.
519 /// db.suggest_item_with_attr(cx, item, "#[derive(Default)]");
521 fn suggest_item_with_attr<D: Display + ?Sized>(
527 applicability: Applicability,
530 /// Suggest to add an item before another.
532 /// The item should not be indented (expect for inner indentation).
537 /// db.suggest_prepend_item(cx, item,
542 fn suggest_prepend_item(&mut self, cx: &T, item: Span, msg: &str, new_item: &str, applicability: Applicability);
544 /// Suggest to completely remove an item.
546 /// This will remove an item and all following whitespace until the next non-whitespace
547 /// character. This should work correctly if item is on the same indentation level as the
553 /// db.suggest_remove_item(cx, item, "remove this")
555 fn suggest_remove_item(&mut self, cx: &T, item: Span, msg: &str, applicability: Applicability);
558 impl<'a, 'b, 'c, T: LintContext> DiagnosticBuilderExt<'c, T> for rustc_errors::DiagnosticBuilder<'b> {
559 fn suggest_item_with_attr<D: Display + ?Sized>(
565 applicability: Applicability,
567 if let Some(indent) = indentation(cx, item) {
568 let span = item.with_hi(item.lo());
570 self.span_suggestion(span, msg, format!("{}\n{}", attr, indent), applicability);
574 fn suggest_prepend_item(&mut self, cx: &T, item: Span, msg: &str, new_item: &str, applicability: Applicability) {
575 if let Some(indent) = indentation(cx, item) {
576 let span = item.with_hi(item.lo());
578 let mut first = true;
579 let new_item = new_item
586 format!("{}{}\n", indent, l)
589 .collect::<String>();
591 self.span_suggestion(span, msg, format!("{}\n{}", new_item, indent), applicability);
595 fn suggest_remove_item(&mut self, cx: &T, item: Span, msg: &str, applicability: Applicability) {
596 let mut remove_span = item;
597 let hi = cx.sess().source_map().next_point(remove_span).hi();
598 let fmpos = cx.sess().source_map().lookup_byte_offset(hi);
600 if let Some(ref src) = fmpos.sf.src {
601 let non_whitespace_offset = src[fmpos.pos.to_usize()..].find(|c| c != ' ' && c != '\t' && c != '\n');
603 if let Some(non_whitespace_offset) = non_whitespace_offset {
604 remove_span = remove_span
605 .with_hi(remove_span.hi() + BytePos(non_whitespace_offset.try_into().expect("offset too large")))
609 self.span_suggestion(remove_span, msg, String::new(), applicability);
616 use std::borrow::Cow;
618 const SUGGESTION: Sugg<'static> = Sugg::NonParen(Cow::Borrowed("function_call()"));
621 fn make_return_transform_sugg_into_a_return_call() {
622 assert_eq!("return function_call()", SUGGESTION.make_return().to_string());
626 fn blockify_transforms_sugg_into_a_block() {
627 assert_eq!("{ function_call() }", SUGGESTION.blockify().to_string());