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};
5 use rustc_ast::util::parser::AssocOp;
6 use rustc_ast::{ast, token};
7 use rustc_ast_pretty::pprust::token_kind_to_string;
8 use rustc_errors::Applicability;
10 use rustc_lint::{EarlyContext, LateContext, LintContext};
11 use rustc_span::source_map::{CharPos, Span};
12 use rustc_span::{BytePos, Pos};
14 use std::convert::TryInto;
15 use std::fmt::Display;
17 /// A helper type to build suggestion correctly handling parenthesis.
19 /// An expression that never needs parenthesis such as `1337` or `[0; 42]`.
20 NonParen(Cow<'a, str>),
21 /// An expression that does not fit in other variants.
22 MaybeParen(Cow<'a, str>),
23 /// A binary operator expression, including `as`-casts and explicit type
25 BinOp(AssocOp, Cow<'a, str>),
28 /// Literal constant `1`, for convenience.
29 pub const ONE: Sugg<'static> = Sugg::NonParen(Cow::Borrowed("1"));
31 impl Display for Sugg<'_> {
32 fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
34 Sugg::NonParen(ref s) | Sugg::MaybeParen(ref s) | Sugg::BinOp(_, ref s) => s.fmt(f),
39 #[allow(clippy::wrong_self_convention)] // ok, because of the function `as_ty` method
41 /// Prepare a suggestion from an expression.
42 pub fn hir_opt(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>) -> Option<Self> {
43 snippet_opt(cx, expr.span).map(|snippet| {
44 let snippet = Cow::Owned(snippet);
45 Self::hir_from_snippet(cx, expr, snippet)
49 /// Convenience function around `hir_opt` for suggestions with a default
51 pub fn hir(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, default: &'a str) -> Self {
52 Self::hir_opt(cx, expr).unwrap_or_else(|| Sugg::NonParen(Cow::Borrowed(default)))
55 /// Same as `hir`, but it adapts the applicability level by following rules:
57 /// - Applicability level `Unspecified` will never be changed.
58 /// - If the span is inside a macro, change the applicability level to `MaybeIncorrect`.
59 /// - If the default value is used and the applicability level is `MachineApplicable`, change it
62 pub fn hir_with_applicability(
63 cx: &LateContext<'_, '_>,
66 applicability: &mut Applicability,
68 if *applicability != Applicability::Unspecified && expr.span.from_expansion() {
69 *applicability = Applicability::MaybeIncorrect;
71 Self::hir_opt(cx, expr).unwrap_or_else(|| {
72 if *applicability == Applicability::MachineApplicable {
73 *applicability = Applicability::HasPlaceholders;
75 Sugg::NonParen(Cow::Borrowed(default))
79 /// Same as `hir`, but will use the pre expansion span if the `expr` was in a macro.
80 pub fn hir_with_macro_callsite(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, default: &'a str) -> Self {
81 let snippet = snippet_with_macro_callsite(cx, expr.span, default);
83 Self::hir_from_snippet(cx, expr, snippet)
86 /// Generate a suggestion for an expression with the given snippet. This is used by the `hir_*`
87 /// function variants of `Sugg`, since these use different snippet functions.
88 fn hir_from_snippet(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, snippet: Cow<'a, str>) -> Self {
89 if let Some(range) = higher::range(cx, expr) {
90 let op = match range.limits {
91 ast::RangeLimits::HalfOpen => AssocOp::DotDot,
92 ast::RangeLimits::Closed => AssocOp::DotDotEq,
94 return Sugg::BinOp(op, snippet);
98 hir::ExprKind::AddrOf(..)
99 | hir::ExprKind::Box(..)
100 | hir::ExprKind::Closure(..)
101 | hir::ExprKind::Unary(..)
102 | hir::ExprKind::Match(..) => Sugg::MaybeParen(snippet),
103 hir::ExprKind::Continue(..)
104 | hir::ExprKind::Yield(..)
105 | hir::ExprKind::Array(..)
106 | hir::ExprKind::Block(..)
107 | hir::ExprKind::Break(..)
108 | hir::ExprKind::Call(..)
109 | hir::ExprKind::Field(..)
110 | hir::ExprKind::Index(..)
111 | hir::ExprKind::LlvmInlineAsm(..)
112 | hir::ExprKind::Lit(..)
113 | hir::ExprKind::Loop(..)
114 | hir::ExprKind::MethodCall(..)
115 | hir::ExprKind::Path(..)
116 | hir::ExprKind::Repeat(..)
117 | hir::ExprKind::Ret(..)
118 | hir::ExprKind::Struct(..)
119 | hir::ExprKind::Tup(..)
120 | hir::ExprKind::DropTemps(_)
121 | hir::ExprKind::Err => Sugg::NonParen(snippet),
122 hir::ExprKind::Assign(..) => Sugg::BinOp(AssocOp::Assign, snippet),
123 hir::ExprKind::AssignOp(op, ..) => Sugg::BinOp(hirbinop2assignop(op), snippet),
124 hir::ExprKind::Binary(op, ..) => Sugg::BinOp(AssocOp::from_ast_binop(higher::binop(op.node)), snippet),
125 hir::ExprKind::Cast(..) => Sugg::BinOp(AssocOp::As, snippet),
126 hir::ExprKind::Type(..) => Sugg::BinOp(AssocOp::Colon, snippet),
130 /// Prepare a suggestion from an expression.
131 pub fn ast(cx: &EarlyContext<'_>, expr: &ast::Expr, default: &'a str) -> Self {
132 use rustc_ast::ast::RangeLimits;
134 let snippet = snippet(cx, expr.span, default);
137 ast::ExprKind::AddrOf(..)
138 | ast::ExprKind::Box(..)
139 | ast::ExprKind::Closure(..)
140 | ast::ExprKind::If(..)
141 | ast::ExprKind::Let(..)
142 | ast::ExprKind::Unary(..)
143 | ast::ExprKind::Match(..) => Sugg::MaybeParen(snippet),
144 ast::ExprKind::Async(..)
145 | ast::ExprKind::Block(..)
146 | ast::ExprKind::Break(..)
147 | ast::ExprKind::Call(..)
148 | ast::ExprKind::Continue(..)
149 | ast::ExprKind::Yield(..)
150 | ast::ExprKind::Field(..)
151 | ast::ExprKind::ForLoop(..)
152 | ast::ExprKind::Index(..)
153 | ast::ExprKind::LlvmInlineAsm(..)
154 | ast::ExprKind::Lit(..)
155 | ast::ExprKind::Loop(..)
156 | ast::ExprKind::MacCall(..)
157 | ast::ExprKind::MethodCall(..)
158 | ast::ExprKind::Paren(..)
159 | ast::ExprKind::Path(..)
160 | ast::ExprKind::Repeat(..)
161 | ast::ExprKind::Ret(..)
162 | ast::ExprKind::Struct(..)
163 | ast::ExprKind::Try(..)
164 | ast::ExprKind::TryBlock(..)
165 | ast::ExprKind::Tup(..)
166 | ast::ExprKind::Array(..)
167 | ast::ExprKind::While(..)
168 | ast::ExprKind::Await(..)
169 | ast::ExprKind::Err => Sugg::NonParen(snippet),
170 ast::ExprKind::Range(.., RangeLimits::HalfOpen) => Sugg::BinOp(AssocOp::DotDot, snippet),
171 ast::ExprKind::Range(.., RangeLimits::Closed) => Sugg::BinOp(AssocOp::DotDotEq, snippet),
172 ast::ExprKind::Assign(..) => Sugg::BinOp(AssocOp::Assign, snippet),
173 ast::ExprKind::AssignOp(op, ..) => Sugg::BinOp(astbinop2assignop(op), snippet),
174 ast::ExprKind::Binary(op, ..) => Sugg::BinOp(AssocOp::from_ast_binop(op.node), snippet),
175 ast::ExprKind::Cast(..) => Sugg::BinOp(AssocOp::As, snippet),
176 ast::ExprKind::Type(..) => Sugg::BinOp(AssocOp::Colon, snippet),
180 /// Convenience method to create the `<lhs> && <rhs>` suggestion.
181 pub fn and(self, rhs: &Self) -> Sugg<'static> {
182 make_binop(ast::BinOpKind::And, &self, rhs)
185 /// Convenience method to create the `<lhs> & <rhs>` suggestion.
186 pub fn bit_and(self, rhs: &Self) -> Sugg<'static> {
187 make_binop(ast::BinOpKind::BitAnd, &self, rhs)
190 /// Convenience method to create the `<lhs> as <rhs>` suggestion.
191 pub fn as_ty<R: Display>(self, rhs: R) -> Sugg<'static> {
192 make_assoc(AssocOp::As, &self, &Sugg::NonParen(rhs.to_string().into()))
195 /// Convenience method to create the `&<expr>` suggestion.
196 pub fn addr(self) -> Sugg<'static> {
200 /// Convenience method to create the `&mut <expr>` suggestion.
201 pub fn mut_addr(self) -> Sugg<'static> {
202 make_unop("&mut ", self)
205 /// Convenience method to create the `*<expr>` suggestion.
206 pub fn deref(self) -> Sugg<'static> {
210 /// Convenience method to create the `&*<expr>` suggestion. Currently this
211 /// is needed because `sugg.deref().addr()` produces an unnecessary set of
212 /// parentheses around the deref.
213 pub fn addr_deref(self) -> Sugg<'static> {
214 make_unop("&*", self)
217 /// Convenience method to create the `&mut *<expr>` suggestion. Currently
218 /// this is needed because `sugg.deref().mut_addr()` produces an unnecessary
219 /// set of parentheses around the deref.
220 pub fn mut_addr_deref(self) -> Sugg<'static> {
221 make_unop("&mut *", self)
224 /// Convenience method to transform suggestion into a return call
225 pub fn make_return(self) -> Sugg<'static> {
226 Sugg::NonParen(Cow::Owned(format!("return {}", self)))
229 /// Convenience method to transform suggestion into a block
230 /// where the suggestion is a trailing expression
231 pub fn blockify(self) -> Sugg<'static> {
232 Sugg::NonParen(Cow::Owned(format!("{{ {} }}", self)))
235 /// Convenience method to create the `<lhs>..<rhs>` or `<lhs>...<rhs>`
238 pub fn range(self, end: &Self, limit: ast::RangeLimits) -> Sugg<'static> {
240 ast::RangeLimits::HalfOpen => make_assoc(AssocOp::DotDot, &self, end),
241 ast::RangeLimits::Closed => make_assoc(AssocOp::DotDotEq, &self, end),
245 /// Adds parenthesis to any expression that might need them. Suitable to the
246 /// `self` argument of a method call
247 /// (e.g., to build `bar.foo()` or `(1 + 2).foo()`).
248 pub fn maybe_par(self) -> Self {
250 Sugg::NonParen(..) => self,
251 // `(x)` and `(x).y()` both don't need additional parens.
252 Sugg::MaybeParen(sugg) => {
253 if sugg.starts_with('(') && sugg.ends_with(')') {
254 Sugg::MaybeParen(sugg)
256 Sugg::NonParen(format!("({})", sugg).into())
259 Sugg::BinOp(_, sugg) => Sugg::NonParen(format!("({})", sugg).into()),
264 impl<'a, 'b> std::ops::Add<Sugg<'b>> for Sugg<'a> {
265 type Output = Sugg<'static>;
266 fn add(self, rhs: Sugg<'b>) -> Sugg<'static> {
267 make_binop(ast::BinOpKind::Add, &self, &rhs)
271 impl<'a, 'b> std::ops::Sub<Sugg<'b>> for Sugg<'a> {
272 type Output = Sugg<'static>;
273 fn sub(self, rhs: Sugg<'b>) -> Sugg<'static> {
274 make_binop(ast::BinOpKind::Sub, &self, &rhs)
278 impl<'a> std::ops::Not for Sugg<'a> {
279 type Output = Sugg<'static>;
280 fn not(self) -> Sugg<'static> {
285 /// Helper type to display either `foo` or `(foo)`.
286 struct ParenHelper<T> {
287 /// `true` if parentheses are needed.
289 /// The main thing to display.
293 impl<T> ParenHelper<T> {
294 /// Builds a `ParenHelper`.
295 fn new(paren: bool, wrapped: T) -> Self {
296 Self { paren, wrapped }
300 impl<T: Display> Display for ParenHelper<T> {
301 fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
303 write!(f, "({})", self.wrapped)
310 /// Builds the string for `<op><expr>` adding parenthesis when necessary.
312 /// For convenience, the operator is taken as a string because all unary
313 /// operators have the same
315 pub fn make_unop(op: &str, expr: Sugg<'_>) -> Sugg<'static> {
316 Sugg::MaybeParen(format!("{}{}", op, expr.maybe_par()).into())
319 /// Builds the string for `<lhs> <op> <rhs>` adding parenthesis when necessary.
321 /// Precedence of shift operator relative to other arithmetic operation is
322 /// often confusing so
323 /// parenthesis will always be added for a mix of these.
324 pub fn make_assoc(op: AssocOp, lhs: &Sugg<'_>, rhs: &Sugg<'_>) -> Sugg<'static> {
325 /// Returns `true` if the operator is a shift operator `<<` or `>>`.
326 fn is_shift(op: &AssocOp) -> bool {
327 matches!(*op, AssocOp::ShiftLeft | AssocOp::ShiftRight)
330 /// Returns `true` if the operator is a arithmetic operator
331 /// (i.e., `+`, `-`, `*`, `/`, `%`).
332 fn is_arith(op: &AssocOp) -> bool {
335 AssocOp::Add | AssocOp::Subtract | AssocOp::Multiply | AssocOp::Divide | AssocOp::Modulus
339 /// Returns `true` if the operator `op` needs parenthesis with the operator
340 /// `other` in the direction `dir`.
341 fn needs_paren(op: &AssocOp, other: &AssocOp, dir: Associativity) -> bool {
342 other.precedence() < op.precedence()
343 || (other.precedence() == op.precedence()
344 && ((op != other && associativity(op) != dir)
345 || (op == other && associativity(op) != Associativity::Both)))
346 || is_shift(op) && is_arith(other)
347 || is_shift(other) && is_arith(op)
350 let lhs_paren = if let Sugg::BinOp(ref lop, _) = *lhs {
351 needs_paren(&op, lop, Associativity::Left)
356 let rhs_paren = if let Sugg::BinOp(ref rop, _) = *rhs {
357 needs_paren(&op, rop, Associativity::Right)
362 let lhs = ParenHelper::new(lhs_paren, lhs);
363 let rhs = ParenHelper::new(rhs_paren, rhs);
364 let sugg = match op {
372 | AssocOp::GreaterEqual
381 | AssocOp::ShiftRight
382 | AssocOp::Subtract => format!(
385 op.to_ast_binop().expect("Those are AST ops").to_string(),
388 AssocOp::Assign => format!("{} = {}", lhs, rhs),
389 AssocOp::AssignOp(op) => format!("{} {}= {}", lhs, token_kind_to_string(&token::BinOp(op)), rhs),
390 AssocOp::As => format!("{} as {}", lhs, rhs),
391 AssocOp::DotDot => format!("{}..{}", lhs, rhs),
392 AssocOp::DotDotEq => format!("{}..={}", lhs, rhs),
393 AssocOp::Colon => format!("{}: {}", lhs, rhs),
396 Sugg::BinOp(op, sugg.into())
399 /// Convenience wrapper around `make_assoc` and `AssocOp::from_ast_binop`.
400 pub fn make_binop(op: ast::BinOpKind, lhs: &Sugg<'_>, rhs: &Sugg<'_>) -> Sugg<'static> {
401 make_assoc(AssocOp::from_ast_binop(op), lhs, rhs)
404 #[derive(PartialEq, Eq, Clone, Copy)]
405 /// Operator associativity.
407 /// The operator is both left-associative and right-associative.
409 /// The operator is left-associative.
411 /// The operator is not associative.
413 /// The operator is right-associative.
417 /// Returns the associativity/fixity of an operator. The difference with
418 /// `AssocOp::fixity` is that an operator can be both left and right associative
419 /// (such as `+`: `a + b + c == (a + b) + c == a + (b + c)`.
421 /// Chained `as` and explicit `:` type coercion never need inner parenthesis so
422 /// they are considered
425 fn associativity(op: &AssocOp) -> Associativity {
426 use rustc_ast::util::parser::AssocOp::{
427 Add, As, Assign, AssignOp, BitAnd, BitOr, BitXor, Colon, Divide, DotDot, DotDotEq, Equal, Greater,
428 GreaterEqual, LAnd, LOr, Less, LessEqual, Modulus, Multiply, NotEqual, ShiftLeft, ShiftRight, Subtract,
432 Assign | AssignOp(_) => Associativity::Right,
433 Add | BitAnd | BitOr | BitXor | LAnd | LOr | Multiply | As | Colon => Associativity::Both,
434 Divide | Equal | Greater | GreaterEqual | Less | LessEqual | Modulus | NotEqual | ShiftLeft | ShiftRight
435 | Subtract => Associativity::Left,
436 DotDot | DotDotEq => Associativity::None,
440 /// Converts a `hir::BinOp` to the corresponding assigning binary operator.
441 fn hirbinop2assignop(op: hir::BinOp) -> AssocOp {
442 use rustc_ast::token::BinOpToken::{And, Caret, Minus, Or, Percent, Plus, Shl, Shr, Slash, Star};
444 AssocOp::AssignOp(match op.node {
445 hir::BinOpKind::Add => Plus,
446 hir::BinOpKind::BitAnd => And,
447 hir::BinOpKind::BitOr => Or,
448 hir::BinOpKind::BitXor => Caret,
449 hir::BinOpKind::Div => Slash,
450 hir::BinOpKind::Mul => Star,
451 hir::BinOpKind::Rem => Percent,
452 hir::BinOpKind::Shl => Shl,
453 hir::BinOpKind::Shr => Shr,
454 hir::BinOpKind::Sub => Minus,
463 | hir::BinOpKind::Or => panic!("This operator does not exist"),
467 /// Converts an `ast::BinOp` to the corresponding assigning binary operator.
468 fn astbinop2assignop(op: ast::BinOp) -> AssocOp {
469 use rustc_ast::ast::BinOpKind::{
470 Add, And, BitAnd, BitOr, BitXor, Div, Eq, Ge, Gt, Le, Lt, Mul, Ne, Or, Rem, Shl, Shr, Sub,
472 use rustc_ast::token::BinOpToken;
474 AssocOp::AssignOp(match op.node {
475 Add => BinOpToken::Plus,
476 BitAnd => BinOpToken::And,
477 BitOr => BinOpToken::Or,
478 BitXor => BinOpToken::Caret,
479 Div => BinOpToken::Slash,
480 Mul => BinOpToken::Star,
481 Rem => BinOpToken::Percent,
482 Shl => BinOpToken::Shl,
483 Shr => BinOpToken::Shr,
484 Sub => BinOpToken::Minus,
485 And | Eq | Ge | Gt | Le | Lt | Ne | Or => panic!("This operator does not exist"),
489 /// Returns the indentation before `span` if there are nothing but `[ \t]`
490 /// before it on its line.
491 fn indentation<T: LintContext>(cx: &T, span: Span) -> Option<String> {
492 let lo = cx.sess().source_map().lookup_char_pos(span.lo());
493 if let Some(line) = lo.file.get_line(lo.line - 1 /* line numbers in `Loc` are 1-based */) {
494 if let Some((pos, _)) = line.char_indices().find(|&(_, c)| c != ' ' && c != '\t') {
495 // We can mix char and byte positions here because we only consider `[ \t]`.
496 if lo.col == CharPos(pos) {
497 Some(line[..pos].into())
509 /// Convenience extension trait for `DiagnosticBuilder`.
510 pub trait DiagnosticBuilderExt<'a, T: LintContext> {
511 /// Suggests to add an attribute to an item.
513 /// Correctly handles indentation of the attribute and item.
518 /// db.suggest_item_with_attr(cx, item, "#[derive(Default)]");
520 fn suggest_item_with_attr<D: Display + ?Sized>(
526 applicability: Applicability,
529 /// Suggest to add an item before another.
531 /// The item should not be indented (expect for inner indentation).
536 /// db.suggest_prepend_item(cx, item,
541 fn suggest_prepend_item(&mut self, cx: &T, item: Span, msg: &str, new_item: &str, applicability: Applicability);
543 /// Suggest to completely remove an item.
545 /// This will remove an item and all following whitespace until the next non-whitespace
546 /// character. This should work correctly if item is on the same indentation level as the
552 /// db.suggest_remove_item(cx, item, "remove this")
554 fn suggest_remove_item(&mut self, cx: &T, item: Span, msg: &str, applicability: Applicability);
557 impl<'a, 'b, 'c, T: LintContext> DiagnosticBuilderExt<'c, T> for rustc_errors::DiagnosticBuilder<'b> {
558 fn suggest_item_with_attr<D: Display + ?Sized>(
564 applicability: Applicability,
566 if let Some(indent) = indentation(cx, item) {
567 let span = item.with_hi(item.lo());
569 self.span_suggestion(span, msg, format!("{}\n{}", attr, indent), applicability);
573 fn suggest_prepend_item(&mut self, cx: &T, item: Span, msg: &str, new_item: &str, applicability: Applicability) {
574 if let Some(indent) = indentation(cx, item) {
575 let span = item.with_hi(item.lo());
577 let mut first = true;
578 let new_item = new_item
585 format!("{}{}\n", indent, l)
588 .collect::<String>();
590 self.span_suggestion(span, msg, format!("{}\n{}", new_item, indent), applicability);
594 fn suggest_remove_item(&mut self, cx: &T, item: Span, msg: &str, applicability: Applicability) {
595 let mut remove_span = item;
596 let hi = cx.sess().source_map().next_point(remove_span).hi();
597 let fmpos = cx.sess().source_map().lookup_byte_offset(hi);
599 if let Some(ref src) = fmpos.sf.src {
600 let non_whitespace_offset = src[fmpos.pos.to_usize()..].find(|c| c != ' ' && c != '\t' && c != '\n');
602 if let Some(non_whitespace_offset) = non_whitespace_offset {
603 remove_span = remove_span
604 .with_hi(remove_span.hi() + BytePos(non_whitespace_offset.try_into().expect("offset too large")))
608 self.span_suggestion(remove_span, msg, String::new(), applicability);
615 use std::borrow::Cow;
617 const SUGGESTION: Sugg<'static> = Sugg::NonParen(Cow::Borrowed("function_call()"));
620 fn make_return_transform_sugg_into_a_return_call() {
621 assert_eq!("return function_call()", SUGGESTION.make_return().to_string());
625 fn blockify_transforms_sugg_into_a_block() {
626 assert_eq!("{ function_call() }", SUGGESTION.blockify().to_string());