1 //! Contains utility functions to generate suggestions.
2 #![deny(clippy::missing_docs_in_private_items)]
4 use crate::utils::{higher, in_macro, snippet, snippet_opt};
7 use rustc::lint::{EarlyContext, LateContext, LintContext};
9 use rustc_errors::Applicability;
12 use std::convert::TryInto;
13 use std::fmt::Display;
15 use syntax::parse::token;
16 use syntax::print::pprust::token_to_string;
17 use syntax::source_map::{CharPos, Span};
18 use syntax::util::parser::AssocOp;
19 use syntax_pos::{BytePos, Pos};
21 /// A helper type to build suggestion correctly handling parenthesis.
23 /// An expression that never needs parenthesis such as `1337` or `[0; 42]`.
24 NonParen(Cow<'a, str>),
25 /// An expression that does not fit in other variants.
26 MaybeParen(Cow<'a, str>),
27 /// A binary operator expression, including `as`-casts and explicit type
29 BinOp(AssocOp, Cow<'a, str>),
32 /// Literal constant `1`, for convenience.
33 pub const ONE: Sugg<'static> = Sugg::NonParen(Cow::Borrowed("1"));
35 impl Display for Sugg<'_> {
36 fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
38 Sugg::NonParen(ref s) | Sugg::MaybeParen(ref s) | Sugg::BinOp(_, ref s) => s.fmt(f),
43 #[allow(clippy::wrong_self_convention)] // ok, because of the function `as_ty` method
45 /// Prepare a suggestion from an expression.
46 pub fn hir_opt(cx: &LateContext<'_, '_>, expr: &hir::Expr) -> Option<Self> {
47 snippet_opt(cx, expr.span).map(|snippet| {
48 let snippet = Cow::Owned(snippet);
50 hir::ExprKind::AddrOf(..)
51 | hir::ExprKind::Box(..)
52 | hir::ExprKind::Closure(.., _)
53 | hir::ExprKind::If(..)
54 | hir::ExprKind::Unary(..)
55 | hir::ExprKind::Match(..) => Sugg::MaybeParen(snippet),
56 hir::ExprKind::Continue(..)
57 | hir::ExprKind::Yield(..)
58 | hir::ExprKind::Array(..)
59 | hir::ExprKind::Block(..)
60 | hir::ExprKind::Break(..)
61 | hir::ExprKind::Call(..)
62 | hir::ExprKind::Field(..)
63 | hir::ExprKind::Index(..)
64 | hir::ExprKind::InlineAsm(..)
65 | hir::ExprKind::Lit(..)
66 | hir::ExprKind::Loop(..)
67 | hir::ExprKind::MethodCall(..)
68 | hir::ExprKind::Path(..)
69 | hir::ExprKind::Repeat(..)
70 | hir::ExprKind::Ret(..)
71 | hir::ExprKind::Struct(..)
72 | hir::ExprKind::Tup(..)
73 | hir::ExprKind::While(..)
74 | hir::ExprKind::Err => Sugg::NonParen(snippet),
75 hir::ExprKind::Assign(..) => Sugg::BinOp(AssocOp::Assign, snippet),
76 hir::ExprKind::AssignOp(op, ..) => Sugg::BinOp(hirbinop2assignop(op), snippet),
77 hir::ExprKind::Binary(op, ..) => Sugg::BinOp(AssocOp::from_ast_binop(higher::binop(op.node)), snippet),
78 hir::ExprKind::Cast(..) => Sugg::BinOp(AssocOp::As, snippet),
79 hir::ExprKind::Type(..) => Sugg::BinOp(AssocOp::Colon, snippet),
84 /// Convenience function around `hir_opt` for suggestions with a default
86 pub fn hir(cx: &LateContext<'_, '_>, expr: &hir::Expr, default: &'a str) -> Self {
87 Self::hir_opt(cx, expr).unwrap_or_else(|| Sugg::NonParen(Cow::Borrowed(default)))
90 /// Same as `hir`, but it adapts the applicability level by following rules:
92 /// - Applicability level `Unspecified` will never be changed.
93 /// - If the span is inside a macro, change the applicability level to `MaybeIncorrect`.
94 /// - If the default value is used and the applicability level is `MachineApplicable`, change it
97 pub fn hir_with_applicability(
98 cx: &LateContext<'_, '_>,
101 applicability: &mut Applicability,
103 if *applicability != Applicability::Unspecified && in_macro(expr.span) {
104 *applicability = Applicability::MaybeIncorrect;
106 Self::hir_opt(cx, expr).unwrap_or_else(|| {
107 if *applicability == Applicability::MachineApplicable {
108 *applicability = Applicability::HasPlaceholders;
110 Sugg::NonParen(Cow::Borrowed(default))
114 /// Prepare a suggestion from an expression.
115 pub fn ast(cx: &EarlyContext<'_>, expr: &ast::Expr, default: &'a str) -> Self {
116 use syntax::ast::RangeLimits;
118 let snippet = snippet(cx, expr.span, default);
121 ast::ExprKind::AddrOf(..)
122 | ast::ExprKind::Box(..)
123 | ast::ExprKind::Closure(..)
124 | ast::ExprKind::If(..)
125 | ast::ExprKind::IfLet(..)
126 | ast::ExprKind::ObsoleteInPlace(..)
127 | ast::ExprKind::Unary(..)
128 | ast::ExprKind::Match(..) => Sugg::MaybeParen(snippet),
129 ast::ExprKind::Async(..)
130 | ast::ExprKind::Block(..)
131 | ast::ExprKind::Break(..)
132 | ast::ExprKind::Call(..)
133 | ast::ExprKind::Continue(..)
134 | ast::ExprKind::Yield(..)
135 | ast::ExprKind::Field(..)
136 | ast::ExprKind::ForLoop(..)
137 | ast::ExprKind::Index(..)
138 | ast::ExprKind::InlineAsm(..)
139 | ast::ExprKind::Lit(..)
140 | ast::ExprKind::Loop(..)
141 | ast::ExprKind::Mac(..)
142 | ast::ExprKind::MethodCall(..)
143 | ast::ExprKind::Paren(..)
144 | ast::ExprKind::Path(..)
145 | ast::ExprKind::Repeat(..)
146 | ast::ExprKind::Ret(..)
147 | ast::ExprKind::Struct(..)
148 | ast::ExprKind::Try(..)
149 | ast::ExprKind::TryBlock(..)
150 | ast::ExprKind::Tup(..)
151 | ast::ExprKind::Array(..)
152 | ast::ExprKind::While(..)
153 | ast::ExprKind::WhileLet(..)
154 | ast::ExprKind::Err => Sugg::NonParen(snippet),
155 ast::ExprKind::Range(.., RangeLimits::HalfOpen) => Sugg::BinOp(AssocOp::DotDot, snippet),
156 ast::ExprKind::Range(.., RangeLimits::Closed) => Sugg::BinOp(AssocOp::DotDotEq, snippet),
157 ast::ExprKind::Assign(..) => Sugg::BinOp(AssocOp::Assign, snippet),
158 ast::ExprKind::AssignOp(op, ..) => Sugg::BinOp(astbinop2assignop(op), snippet),
159 ast::ExprKind::Binary(op, ..) => Sugg::BinOp(AssocOp::from_ast_binop(op.node), snippet),
160 ast::ExprKind::Cast(..) => Sugg::BinOp(AssocOp::As, snippet),
161 ast::ExprKind::Type(..) => Sugg::BinOp(AssocOp::Colon, snippet),
165 /// Convenience method to create the `<lhs> && <rhs>` suggestion.
166 pub fn and(self, rhs: &Self) -> Sugg<'static> {
167 make_binop(ast::BinOpKind::And, &self, rhs)
170 /// Convenience method to create the `<lhs> & <rhs>` suggestion.
171 pub fn bit_and(self, rhs: &Self) -> Sugg<'static> {
172 make_binop(ast::BinOpKind::BitAnd, &self, rhs)
175 /// Convenience method to create the `<lhs> as <rhs>` suggestion.
176 pub fn as_ty<R: Display>(self, rhs: R) -> Sugg<'static> {
177 make_assoc(AssocOp::As, &self, &Sugg::NonParen(rhs.to_string().into()))
180 /// Convenience method to create the `&<expr>` suggestion.
181 pub fn addr(self) -> Sugg<'static> {
185 /// Convenience method to create the `&mut <expr>` suggestion.
186 pub fn mut_addr(self) -> Sugg<'static> {
187 make_unop("&mut ", self)
190 /// Convenience method to create the `*<expr>` suggestion.
191 pub fn deref(self) -> Sugg<'static> {
195 /// Convenience method to create the `&*<expr>` suggestion. Currently this
196 /// is needed because `sugg.deref().addr()` produces an unnecessary set of
197 /// parentheses around the deref.
198 pub fn addr_deref(self) -> Sugg<'static> {
199 make_unop("&*", self)
202 /// Convenience method to create the `&mut *<expr>` suggestion. Currently
203 /// this is needed because `sugg.deref().mut_addr()` produces an unnecessary
204 /// set of parentheses around the deref.
205 pub fn mut_addr_deref(self) -> Sugg<'static> {
206 make_unop("&mut *", self)
209 /// Convenience method to transform suggestion into a return call
210 pub fn make_return(self) -> Sugg<'static> {
211 Sugg::NonParen(Cow::Owned(format!("return {}", self)))
214 /// Convenience method to transform suggestion into a block
215 /// where the suggestion is a trailing expression
216 pub fn blockify(self) -> Sugg<'static> {
217 Sugg::NonParen(Cow::Owned(format!("{{ {} }}", self)))
220 /// Convenience method to create the `<lhs>..<rhs>` or `<lhs>...<rhs>`
223 pub fn range(self, end: &Self, limit: ast::RangeLimits) -> Sugg<'static> {
225 ast::RangeLimits::HalfOpen => make_assoc(AssocOp::DotDot, &self, end),
226 ast::RangeLimits::Closed => make_assoc(AssocOp::DotDotEq, &self, end),
230 /// Add parenthesis to any expression that might need them. Suitable to the
231 /// `self` argument of
232 /// a method call (eg. to build `bar.foo()` or `(1 + 2).foo()`).
233 pub fn maybe_par(self) -> Self {
235 Sugg::NonParen(..) => self,
236 // (x) and (x).y() both don't need additional parens
237 Sugg::MaybeParen(sugg) => {
238 if sugg.starts_with('(') && sugg.ends_with(')') {
239 Sugg::MaybeParen(sugg)
241 Sugg::NonParen(format!("({})", sugg).into())
244 Sugg::BinOp(_, sugg) => Sugg::NonParen(format!("({})", sugg).into()),
249 impl<'a, 'b> std::ops::Add<Sugg<'b>> for Sugg<'a> {
250 type Output = Sugg<'static>;
251 fn add(self, rhs: Sugg<'b>) -> Sugg<'static> {
252 make_binop(ast::BinOpKind::Add, &self, &rhs)
256 impl<'a, 'b> std::ops::Sub<Sugg<'b>> for Sugg<'a> {
257 type Output = Sugg<'static>;
258 fn sub(self, rhs: Sugg<'b>) -> Sugg<'static> {
259 make_binop(ast::BinOpKind::Sub, &self, &rhs)
263 impl<'a> std::ops::Not for Sugg<'a> {
264 type Output = Sugg<'static>;
265 fn not(self) -> Sugg<'static> {
270 /// Helper type to display either `foo` or `(foo)`.
271 struct ParenHelper<T> {
272 /// Whether parenthesis are needed.
274 /// The main thing to display.
278 impl<T> ParenHelper<T> {
279 /// Build a `ParenHelper`.
280 fn new(paren: bool, wrapped: T) -> Self {
281 Self { paren, wrapped }
285 impl<T: Display> Display for ParenHelper<T> {
286 fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
288 write!(f, "({})", self.wrapped)
295 /// Build the string for `<op><expr>` adding parenthesis when necessary.
297 /// For convenience, the operator is taken as a string because all unary
298 /// operators have the same
300 pub fn make_unop(op: &str, expr: Sugg<'_>) -> Sugg<'static> {
301 Sugg::MaybeParen(format!("{}{}", op, expr.maybe_par()).into())
304 /// Build the string for `<lhs> <op> <rhs>` adding parenthesis when necessary.
306 /// Precedence of shift operator relative to other arithmetic operation is
307 /// often confusing so
308 /// parenthesis will always be added for a mix of these.
309 pub fn make_assoc(op: AssocOp, lhs: &Sugg<'_>, rhs: &Sugg<'_>) -> Sugg<'static> {
310 /// Whether the operator is a shift operator `<<` or `>>`.
311 fn is_shift(op: &AssocOp) -> bool {
312 matches!(*op, AssocOp::ShiftLeft | AssocOp::ShiftRight)
315 /// Whether the operator is a arithmetic operator (`+`, `-`, `*`, `/`, `%`).
316 fn is_arith(op: &AssocOp) -> bool {
319 AssocOp::Add | AssocOp::Subtract | AssocOp::Multiply | AssocOp::Divide | AssocOp::Modulus
323 /// Whether the operator `op` needs parenthesis with the operator `other`
326 fn needs_paren(op: &AssocOp, other: &AssocOp, dir: Associativity) -> bool {
327 other.precedence() < op.precedence()
328 || (other.precedence() == op.precedence()
329 && ((op != other && associativity(op) != dir)
330 || (op == other && associativity(op) != Associativity::Both)))
331 || is_shift(op) && is_arith(other)
332 || is_shift(other) && is_arith(op)
335 let lhs_paren = if let Sugg::BinOp(ref lop, _) = *lhs {
336 needs_paren(&op, lop, Associativity::Left)
341 let rhs_paren = if let Sugg::BinOp(ref rop, _) = *rhs {
342 needs_paren(&op, rop, Associativity::Right)
347 let lhs = ParenHelper::new(lhs_paren, lhs);
348 let rhs = ParenHelper::new(rhs_paren, rhs);
349 let sugg = match op {
357 | AssocOp::GreaterEqual
366 | AssocOp::ShiftRight
367 | AssocOp::Subtract => format!(
370 op.to_ast_binop().expect("Those are AST ops").to_string(),
373 AssocOp::Assign => format!("{} = {}", lhs, rhs),
374 AssocOp::ObsoleteInPlace => format!("in ({}) {}", lhs, rhs),
375 AssocOp::AssignOp(op) => format!("{} {}= {}", lhs, token_to_string(&token::BinOp(op)), rhs),
376 AssocOp::As => format!("{} as {}", lhs, rhs),
377 AssocOp::DotDot => format!("{}..{}", lhs, rhs),
378 AssocOp::DotDotEq => format!("{}..={}", lhs, rhs),
379 AssocOp::Colon => format!("{}: {}", lhs, rhs),
382 Sugg::BinOp(op, sugg.into())
385 /// Convenience wrapper around `make_assoc` and `AssocOp::from_ast_binop`.
386 pub fn make_binop(op: ast::BinOpKind, lhs: &Sugg<'_>, rhs: &Sugg<'_>) -> Sugg<'static> {
387 make_assoc(AssocOp::from_ast_binop(op), lhs, rhs)
390 #[derive(PartialEq, Eq, Clone, Copy)]
391 /// Operator associativity.
393 /// The operator is both left-associative and right-associative.
395 /// The operator is left-associative.
397 /// The operator is not associative.
399 /// The operator is right-associative.
403 /// Return the associativity/fixity of an operator. The difference with
404 /// `AssocOp::fixity` is that
405 /// an operator can be both left and right associative (such as `+`:
406 /// `a + b + c == (a + b) + c == a + (b + c)`.
408 /// Chained `as` and explicit `:` type coercion never need inner parenthesis so
409 /// they are considered
411 fn associativity(op: &AssocOp) -> Associativity {
412 use syntax::util::parser::AssocOp::*;
415 ObsoleteInPlace | Assign | AssignOp(_) => Associativity::Right,
416 Add | BitAnd | BitOr | BitXor | LAnd | LOr | Multiply | As | Colon => Associativity::Both,
417 Divide | Equal | Greater | GreaterEqual | Less | LessEqual | Modulus | NotEqual | ShiftLeft | ShiftRight
418 | Subtract => Associativity::Left,
419 DotDot | DotDotEq => Associativity::None,
423 /// Convert a `hir::BinOp` to the corresponding assigning binary operator.
424 fn hirbinop2assignop(op: hir::BinOp) -> AssocOp {
425 use syntax::parse::token::BinOpToken::*;
427 AssocOp::AssignOp(match op.node {
428 hir::BinOpKind::Add => Plus,
429 hir::BinOpKind::BitAnd => And,
430 hir::BinOpKind::BitOr => Or,
431 hir::BinOpKind::BitXor => Caret,
432 hir::BinOpKind::Div => Slash,
433 hir::BinOpKind::Mul => Star,
434 hir::BinOpKind::Rem => Percent,
435 hir::BinOpKind::Shl => Shl,
436 hir::BinOpKind::Shr => Shr,
437 hir::BinOpKind::Sub => Minus,
446 | hir::BinOpKind::Or => panic!("This operator does not exist"),
450 /// Convert an `ast::BinOp` to the corresponding assigning binary operator.
451 fn astbinop2assignop(op: ast::BinOp) -> AssocOp {
452 use syntax::ast::BinOpKind::*;
453 use syntax::parse::token::BinOpToken;
455 AssocOp::AssignOp(match op.node {
456 Add => BinOpToken::Plus,
457 BitAnd => BinOpToken::And,
458 BitOr => BinOpToken::Or,
459 BitXor => BinOpToken::Caret,
460 Div => BinOpToken::Slash,
461 Mul => BinOpToken::Star,
462 Rem => BinOpToken::Percent,
463 Shl => BinOpToken::Shl,
464 Shr => BinOpToken::Shr,
465 Sub => BinOpToken::Minus,
466 And | Eq | Ge | Gt | Le | Lt | Ne | Or => panic!("This operator does not exist"),
470 /// Return the indentation before `span` if there are nothing but `[ \t]`
471 /// before it on its line.
472 fn indentation<'a, T: LintContext<'a>>(cx: &T, span: Span) -> Option<String> {
473 let lo = cx.sess().source_map().lookup_char_pos(span.lo());
474 if let Some(line) = lo.file.get_line(lo.line - 1 /* line numbers in `Loc` are 1-based */) {
475 if let Some((pos, _)) = line.char_indices().find(|&(_, c)| c != ' ' && c != '\t') {
476 // we can mix char and byte positions here because we only consider `[ \t]`
477 if lo.col == CharPos(pos) {
478 Some(line[..pos].into())
490 /// Convenience extension trait for `DiagnosticBuilder`.
491 pub trait DiagnosticBuilderExt<'a, T: LintContext<'a>> {
492 /// Suggests to add an attribute to an item.
494 /// Correctly handles indentation of the attribute and item.
499 /// db.suggest_item_with_attr(cx, item, "#[derive(Default)]");
501 fn suggest_item_with_attr<D: Display + ?Sized>(
507 applicability: Applicability,
510 /// Suggest to add an item before another.
512 /// The item should not be indented (expect for inner indentation).
517 /// db.suggest_prepend_item(cx, item,
522 fn suggest_prepend_item(&mut self, cx: &T, item: Span, msg: &str, new_item: &str, applicability: Applicability);
524 /// Suggest to completely remove an item.
526 /// This will remove an item and all following whitespace until the next non-whitespace
527 /// character. This should work correctly if item is on the same indentation level as the
533 /// db.suggest_remove_item(cx, item, "remove this")
535 fn suggest_remove_item(&mut self, cx: &T, item: Span, msg: &str, applicability: Applicability);
538 impl<'a, 'b, 'c, T: LintContext<'c>> DiagnosticBuilderExt<'c, T> for rustc_errors::DiagnosticBuilder<'b> {
539 fn suggest_item_with_attr<D: Display + ?Sized>(
545 applicability: Applicability,
547 if let Some(indent) = indentation(cx, item) {
548 let span = item.with_hi(item.lo());
550 self.span_suggestion_with_applicability(span, msg, format!("{}\n{}", attr, indent), applicability);
554 fn suggest_prepend_item(&mut self, cx: &T, item: Span, msg: &str, new_item: &str, applicability: Applicability) {
555 if let Some(indent) = indentation(cx, item) {
556 let span = item.with_hi(item.lo());
558 let mut first = true;
559 let new_item = new_item
566 format!("{}{}\n", indent, l)
569 .collect::<String>();
571 self.span_suggestion_with_applicability(span, msg, format!("{}\n{}", new_item, indent), applicability);
575 fn suggest_remove_item(&mut self, cx: &T, item: Span, msg: &str, applicability: Applicability) {
576 let mut remove_span = item;
577 let hi = cx.sess().source_map().next_point(remove_span).hi();
578 let fmpos = cx.sess().source_map().lookup_byte_offset(hi);
580 if let Some(ref src) = fmpos.sf.src {
581 let non_whitespace_offset = src[fmpos.pos.to_usize()..].find(|c| c != ' ' && c != '\t' && c != '\n');
583 if let Some(non_whitespace_offset) = non_whitespace_offset {
584 remove_span = remove_span
585 .with_hi(remove_span.hi() + BytePos(non_whitespace_offset.try_into().expect("offset too large")))
589 self.span_suggestion_with_applicability(remove_span, msg, String::new(), applicability);
596 use std::borrow::Cow;
598 const SUGGESTION: Sugg<'static> = Sugg::NonParen(Cow::Borrowed("function_call()"));
601 fn make_return_transform_sugg_into_a_return_call() {
602 assert_eq!("return function_call()", SUGGESTION.make_return().to_string());
606 fn blockify_transforms_sugg_into_a_block() {
607 assert_eq!("{ function_call() }", SUGGESTION.blockify().to_string());