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};
7 use rustc::lint::{EarlyContext, LateContext, LintContext};
8 use rustc_errors::Applicability;
10 use std::convert::TryInto;
11 use std::fmt::Display;
13 use syntax::print::pprust::token_kind_to_string;
14 use syntax::source_map::{CharPos, Span};
16 use syntax::util::parser::AssocOp;
17 use syntax_pos::{BytePos, Pos};
19 pub use crate::literal_representation::format_numeric_literal;
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);
49 Self::hir_from_snippet(cx, expr, snippet)
53 /// Convenience function around `hir_opt` for suggestions with a default
55 pub fn hir(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, default: &'a str) -> Self {
56 Self::hir_opt(cx, expr).unwrap_or_else(|| Sugg::NonParen(Cow::Borrowed(default)))
59 /// Same as `hir`, but it adapts the applicability level by following rules:
61 /// - Applicability level `Unspecified` will never be changed.
62 /// - If the span is inside a macro, change the applicability level to `MaybeIncorrect`.
63 /// - If the default value is used and the applicability level is `MachineApplicable`, change it
66 pub fn hir_with_applicability(
67 cx: &LateContext<'_, '_>,
70 applicability: &mut Applicability,
72 if *applicability != Applicability::Unspecified && expr.span.from_expansion() {
73 *applicability = Applicability::MaybeIncorrect;
75 Self::hir_opt(cx, expr).unwrap_or_else(|| {
76 if *applicability == Applicability::MachineApplicable {
77 *applicability = Applicability::HasPlaceholders;
79 Sugg::NonParen(Cow::Borrowed(default))
83 /// Same as `hir`, but will use the pre expansion span if the `expr` was in a macro.
84 pub fn hir_with_macro_callsite(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, default: &'a str) -> Self {
85 let snippet = snippet_with_macro_callsite(cx, expr.span, default);
87 Self::hir_from_snippet(cx, expr, snippet)
90 /// Generate a suggestion for an expression with the given snippet. This is used by the `hir_*`
91 /// function variants of `Sugg`, since these use different snippet functions.
92 fn hir_from_snippet(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, snippet: Cow<'a, str>) -> Self {
93 if let Some(range) = higher::range(cx, expr) {
94 let op = match range.limits {
95 ast::RangeLimits::HalfOpen => AssocOp::DotDot,
96 ast::RangeLimits::Closed => AssocOp::DotDotEq,
98 return Sugg::BinOp(op, snippet);
102 hir::ExprKind::AddrOf(..)
103 | hir::ExprKind::Box(..)
104 | hir::ExprKind::Closure(..)
105 | hir::ExprKind::Unary(..)
106 | hir::ExprKind::Match(..) => Sugg::MaybeParen(snippet),
107 hir::ExprKind::Continue(..)
108 | hir::ExprKind::Yield(..)
109 | hir::ExprKind::Array(..)
110 | hir::ExprKind::Block(..)
111 | hir::ExprKind::Break(..)
112 | hir::ExprKind::Call(..)
113 | hir::ExprKind::Field(..)
114 | hir::ExprKind::Index(..)
115 | hir::ExprKind::InlineAsm(..)
116 | hir::ExprKind::Lit(..)
117 | hir::ExprKind::Loop(..)
118 | hir::ExprKind::MethodCall(..)
119 | hir::ExprKind::Path(..)
120 | hir::ExprKind::Repeat(..)
121 | hir::ExprKind::Ret(..)
122 | hir::ExprKind::Struct(..)
123 | hir::ExprKind::Tup(..)
124 | hir::ExprKind::DropTemps(_)
125 | hir::ExprKind::Err => Sugg::NonParen(snippet),
126 hir::ExprKind::Assign(..) => Sugg::BinOp(AssocOp::Assign, snippet),
127 hir::ExprKind::AssignOp(op, ..) => Sugg::BinOp(hirbinop2assignop(op), snippet),
128 hir::ExprKind::Binary(op, ..) => Sugg::BinOp(AssocOp::from_ast_binop(higher::binop(op.node)), snippet),
129 hir::ExprKind::Cast(..) => Sugg::BinOp(AssocOp::As, snippet),
130 hir::ExprKind::Type(..) => Sugg::BinOp(AssocOp::Colon, snippet),
134 /// Prepare a suggestion from an expression.
135 pub fn ast(cx: &EarlyContext<'_>, expr: &ast::Expr, default: &'a str) -> Self {
136 use syntax::ast::RangeLimits;
138 let snippet = snippet(cx, expr.span, default);
141 ast::ExprKind::AddrOf(..)
142 | ast::ExprKind::Box(..)
143 | ast::ExprKind::Closure(..)
144 | ast::ExprKind::If(..)
145 | ast::ExprKind::Let(..)
146 | ast::ExprKind::Unary(..)
147 | ast::ExprKind::Match(..) => Sugg::MaybeParen(snippet),
148 ast::ExprKind::Async(..)
149 | ast::ExprKind::Block(..)
150 | ast::ExprKind::Break(..)
151 | ast::ExprKind::Call(..)
152 | ast::ExprKind::Continue(..)
153 | ast::ExprKind::Yield(..)
154 | ast::ExprKind::Field(..)
155 | ast::ExprKind::ForLoop(..)
156 | ast::ExprKind::Index(..)
157 | ast::ExprKind::InlineAsm(..)
158 | ast::ExprKind::Lit(..)
159 | ast::ExprKind::Loop(..)
160 | ast::ExprKind::Mac(..)
161 | ast::ExprKind::MethodCall(..)
162 | ast::ExprKind::Paren(..)
163 | ast::ExprKind::Path(..)
164 | ast::ExprKind::Repeat(..)
165 | ast::ExprKind::Ret(..)
166 | ast::ExprKind::Struct(..)
167 | ast::ExprKind::Try(..)
168 | ast::ExprKind::TryBlock(..)
169 | ast::ExprKind::Tup(..)
170 | ast::ExprKind::Array(..)
171 | ast::ExprKind::While(..)
172 | ast::ExprKind::Await(..)
173 | ast::ExprKind::Err => Sugg::NonParen(snippet),
174 ast::ExprKind::Range(.., RangeLimits::HalfOpen) => Sugg::BinOp(AssocOp::DotDot, snippet),
175 ast::ExprKind::Range(.., RangeLimits::Closed) => Sugg::BinOp(AssocOp::DotDotEq, snippet),
176 ast::ExprKind::Assign(..) => Sugg::BinOp(AssocOp::Assign, snippet),
177 ast::ExprKind::AssignOp(op, ..) => Sugg::BinOp(astbinop2assignop(op), snippet),
178 ast::ExprKind::Binary(op, ..) => Sugg::BinOp(AssocOp::from_ast_binop(op.node), snippet),
179 ast::ExprKind::Cast(..) => Sugg::BinOp(AssocOp::As, snippet),
180 ast::ExprKind::Type(..) => Sugg::BinOp(AssocOp::Colon, snippet),
184 /// Convenience method to create the `<lhs> && <rhs>` suggestion.
185 pub fn and(self, rhs: &Self) -> Sugg<'static> {
186 make_binop(ast::BinOpKind::And, &self, rhs)
189 /// Convenience method to create the `<lhs> & <rhs>` suggestion.
190 pub fn bit_and(self, rhs: &Self) -> Sugg<'static> {
191 make_binop(ast::BinOpKind::BitAnd, &self, rhs)
194 /// Convenience method to create the `<lhs> as <rhs>` suggestion.
195 pub fn as_ty<R: Display>(self, rhs: R) -> Sugg<'static> {
196 make_assoc(AssocOp::As, &self, &Sugg::NonParen(rhs.to_string().into()))
199 /// Convenience method to create the `&<expr>` suggestion.
200 pub fn addr(self) -> Sugg<'static> {
204 /// Convenience method to create the `&mut <expr>` suggestion.
205 pub fn mut_addr(self) -> Sugg<'static> {
206 make_unop("&mut ", self)
209 /// Convenience method to create the `*<expr>` suggestion.
210 pub fn deref(self) -> Sugg<'static> {
214 /// Convenience method to create the `&*<expr>` suggestion. Currently this
215 /// is needed because `sugg.deref().addr()` produces an unnecessary set of
216 /// parentheses around the deref.
217 pub fn addr_deref(self) -> Sugg<'static> {
218 make_unop("&*", self)
221 /// Convenience method to create the `&mut *<expr>` suggestion. Currently
222 /// this is needed because `sugg.deref().mut_addr()` produces an unnecessary
223 /// set of parentheses around the deref.
224 pub fn mut_addr_deref(self) -> Sugg<'static> {
225 make_unop("&mut *", self)
228 /// Convenience method to transform suggestion into a return call
229 pub fn make_return(self) -> Sugg<'static> {
230 Sugg::NonParen(Cow::Owned(format!("return {}", self)))
233 /// Convenience method to transform suggestion into a block
234 /// where the suggestion is a trailing expression
235 pub fn blockify(self) -> Sugg<'static> {
236 Sugg::NonParen(Cow::Owned(format!("{{ {} }}", self)))
239 /// Convenience method to create the `<lhs>..<rhs>` or `<lhs>...<rhs>`
242 pub fn range(self, end: &Self, limit: ast::RangeLimits) -> Sugg<'static> {
244 ast::RangeLimits::HalfOpen => make_assoc(AssocOp::DotDot, &self, end),
245 ast::RangeLimits::Closed => make_assoc(AssocOp::DotDotEq, &self, end),
249 /// Adds parenthesis to any expression that might need them. Suitable to the
250 /// `self` argument of a method call
251 /// (e.g., to build `bar.foo()` or `(1 + 2).foo()`).
252 pub fn maybe_par(self) -> Self {
254 Sugg::NonParen(..) => self,
255 // `(x)` and `(x).y()` both don't need additional parens.
256 Sugg::MaybeParen(sugg) => {
257 if sugg.starts_with('(') && sugg.ends_with(')') {
258 Sugg::MaybeParen(sugg)
260 Sugg::NonParen(format!("({})", sugg).into())
263 Sugg::BinOp(_, sugg) => Sugg::NonParen(format!("({})", sugg).into()),
268 impl<'a, 'b> std::ops::Add<Sugg<'b>> for Sugg<'a> {
269 type Output = Sugg<'static>;
270 fn add(self, rhs: Sugg<'b>) -> Sugg<'static> {
271 make_binop(ast::BinOpKind::Add, &self, &rhs)
275 impl<'a, 'b> std::ops::Sub<Sugg<'b>> for Sugg<'a> {
276 type Output = Sugg<'static>;
277 fn sub(self, rhs: Sugg<'b>) -> Sugg<'static> {
278 make_binop(ast::BinOpKind::Sub, &self, &rhs)
282 impl<'a> std::ops::Not for Sugg<'a> {
283 type Output = Sugg<'static>;
284 fn not(self) -> Sugg<'static> {
289 /// Helper type to display either `foo` or `(foo)`.
290 struct ParenHelper<T> {
291 /// `true` if parentheses are needed.
293 /// The main thing to display.
297 impl<T> ParenHelper<T> {
298 /// Builds a `ParenHelper`.
299 fn new(paren: bool, wrapped: T) -> Self {
300 Self { paren, wrapped }
304 impl<T: Display> Display for ParenHelper<T> {
305 fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
307 write!(f, "({})", self.wrapped)
314 /// Builds the string for `<op><expr>` adding parenthesis when necessary.
316 /// For convenience, the operator is taken as a string because all unary
317 /// operators have the same
319 pub fn make_unop(op: &str, expr: Sugg<'_>) -> Sugg<'static> {
320 Sugg::MaybeParen(format!("{}{}", op, expr.maybe_par()).into())
323 /// Builds the string for `<lhs> <op> <rhs>` adding parenthesis when necessary.
325 /// Precedence of shift operator relative to other arithmetic operation is
326 /// often confusing so
327 /// parenthesis will always be added for a mix of these.
328 pub fn make_assoc(op: AssocOp, lhs: &Sugg<'_>, rhs: &Sugg<'_>) -> Sugg<'static> {
329 /// Returns `true` if the operator is a shift operator `<<` or `>>`.
330 fn is_shift(op: &AssocOp) -> bool {
331 matches!(*op, AssocOp::ShiftLeft | AssocOp::ShiftRight)
334 /// Returns `true` if the operator is a arithmetic operator
335 /// (i.e., `+`, `-`, `*`, `/`, `%`).
336 fn is_arith(op: &AssocOp) -> bool {
339 AssocOp::Add | AssocOp::Subtract | AssocOp::Multiply | AssocOp::Divide | AssocOp::Modulus
343 /// Returns `true` if the operator `op` needs parenthesis with the operator
344 /// `other` in the direction `dir`.
345 fn needs_paren(op: &AssocOp, other: &AssocOp, dir: Associativity) -> bool {
346 other.precedence() < op.precedence()
347 || (other.precedence() == op.precedence()
348 && ((op != other && associativity(op) != dir)
349 || (op == other && associativity(op) != Associativity::Both)))
350 || is_shift(op) && is_arith(other)
351 || is_shift(other) && is_arith(op)
354 let lhs_paren = if let Sugg::BinOp(ref lop, _) = *lhs {
355 needs_paren(&op, lop, Associativity::Left)
360 let rhs_paren = if let Sugg::BinOp(ref rop, _) = *rhs {
361 needs_paren(&op, rop, Associativity::Right)
366 let lhs = ParenHelper::new(lhs_paren, lhs);
367 let rhs = ParenHelper::new(rhs_paren, rhs);
368 let sugg = match op {
376 | AssocOp::GreaterEqual
385 | AssocOp::ShiftRight
386 | AssocOp::Subtract => format!(
389 op.to_ast_binop().expect("Those are AST ops").to_string(),
392 AssocOp::Assign => format!("{} = {}", lhs, rhs),
393 AssocOp::AssignOp(op) => format!("{} {}= {}", lhs, token_kind_to_string(&token::BinOp(op)), rhs),
394 AssocOp::As => format!("{} as {}", lhs, rhs),
395 AssocOp::DotDot => format!("{}..{}", lhs, rhs),
396 AssocOp::DotDotEq => format!("{}..={}", lhs, rhs),
397 AssocOp::Colon => format!("{}: {}", lhs, rhs),
400 Sugg::BinOp(op, sugg.into())
403 /// Convenience wrapper around `make_assoc` and `AssocOp::from_ast_binop`.
404 pub fn make_binop(op: ast::BinOpKind, lhs: &Sugg<'_>, rhs: &Sugg<'_>) -> Sugg<'static> {
405 make_assoc(AssocOp::from_ast_binop(op), lhs, rhs)
408 #[derive(PartialEq, Eq, Clone, Copy)]
409 /// Operator associativity.
411 /// The operator is both left-associative and right-associative.
413 /// The operator is left-associative.
415 /// The operator is not associative.
417 /// The operator is right-associative.
421 /// Returns the associativity/fixity of an operator. The difference with
422 /// `AssocOp::fixity` is that an operator can be both left and right associative
423 /// (such as `+`: `a + b + c == (a + b) + c == a + (b + c)`.
425 /// Chained `as` and explicit `:` type coercion never need inner parenthesis so
426 /// they are considered
429 fn associativity(op: &AssocOp) -> Associativity {
430 use syntax::util::parser::AssocOp::*;
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 syntax::token::BinOpToken::*;
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 syntax::ast::BinOpKind::*;
471 use syntax::token::BinOpToken;
473 AssocOp::AssignOp(match op.node {
474 Add => BinOpToken::Plus,
475 BitAnd => BinOpToken::And,
476 BitOr => BinOpToken::Or,
477 BitXor => BinOpToken::Caret,
478 Div => BinOpToken::Slash,
479 Mul => BinOpToken::Star,
480 Rem => BinOpToken::Percent,
481 Shl => BinOpToken::Shl,
482 Shr => BinOpToken::Shr,
483 Sub => BinOpToken::Minus,
484 And | Eq | Ge | Gt | Le | Lt | Ne | Or => panic!("This operator does not exist"),
488 /// Returns the indentation before `span` if there are nothing but `[ \t]`
489 /// before it on its line.
490 fn indentation<T: LintContext>(cx: &T, span: Span) -> Option<String> {
491 let lo = cx.sess().source_map().lookup_char_pos(span.lo());
492 if let Some(line) = lo.file.get_line(lo.line - 1 /* line numbers in `Loc` are 1-based */) {
493 if let Some((pos, _)) = line.char_indices().find(|&(_, c)| c != ' ' && c != '\t') {
494 // We can mix char and byte positions here because we only consider `[ \t]`.
495 if lo.col == CharPos(pos) {
496 Some(line[..pos].into())
508 /// Convenience extension trait for `DiagnosticBuilder`.
509 pub trait DiagnosticBuilderExt<'a, T: LintContext> {
510 /// Suggests to add an attribute to an item.
512 /// Correctly handles indentation of the attribute and item.
517 /// db.suggest_item_with_attr(cx, item, "#[derive(Default)]");
519 fn suggest_item_with_attr<D: Display + ?Sized>(
525 applicability: Applicability,
528 /// Suggest to add an item before another.
530 /// The item should not be indented (expect for inner indentation).
535 /// db.suggest_prepend_item(cx, item,
540 fn suggest_prepend_item(&mut self, cx: &T, item: Span, msg: &str, new_item: &str, applicability: Applicability);
542 /// Suggest to completely remove an item.
544 /// This will remove an item and all following whitespace until the next non-whitespace
545 /// character. This should work correctly if item is on the same indentation level as the
551 /// db.suggest_remove_item(cx, item, "remove this")
553 fn suggest_remove_item(&mut self, cx: &T, item: Span, msg: &str, applicability: Applicability);
556 impl<'a, 'b, 'c, T: LintContext> DiagnosticBuilderExt<'c, T> for rustc_errors::DiagnosticBuilder<'b> {
557 fn suggest_item_with_attr<D: Display + ?Sized>(
563 applicability: Applicability,
565 if let Some(indent) = indentation(cx, item) {
566 let span = item.with_hi(item.lo());
568 self.span_suggestion(span, msg, format!("{}\n{}", attr, indent), applicability);
572 fn suggest_prepend_item(&mut self, cx: &T, item: Span, msg: &str, new_item: &str, applicability: Applicability) {
573 if let Some(indent) = indentation(cx, item) {
574 let span = item.with_hi(item.lo());
576 let mut first = true;
577 let new_item = new_item
584 format!("{}{}\n", indent, l)
587 .collect::<String>();
589 self.span_suggestion(span, msg, format!("{}\n{}", new_item, indent), applicability);
593 fn suggest_remove_item(&mut self, cx: &T, item: Span, msg: &str, applicability: Applicability) {
594 let mut remove_span = item;
595 let hi = cx.sess().source_map().next_point(remove_span).hi();
596 let fmpos = cx.sess().source_map().lookup_byte_offset(hi);
598 if let Some(ref src) = fmpos.sf.src {
599 let non_whitespace_offset = src[fmpos.pos.to_usize()..].find(|c| c != ' ' && c != '\t' && c != '\n');
601 if let Some(non_whitespace_offset) = non_whitespace_offset {
602 remove_span = remove_span
603 .with_hi(remove_span.hi() + BytePos(non_whitespace_offset.try_into().expect("offset too large")))
607 self.span_suggestion(remove_span, msg, String::new(), applicability);
614 use std::borrow::Cow;
616 const SUGGESTION: Sugg<'static> = Sugg::NonParen(Cow::Borrowed("function_call()"));
619 fn make_return_transform_sugg_into_a_return_call() {
620 assert_eq!("return function_call()", SUGGESTION.make_return().to_string());
624 fn blockify_transforms_sugg_into_a_block() {
625 assert_eq!("{ function_call() }", SUGGESTION.blockify().to_string());