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};
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_kind_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);
49 Self::hir_from_snippet(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(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(expr: &hir::Expr, snippet: Cow<'a, str>) -> Self {
94 hir::ExprKind::AddrOf(..)
95 | hir::ExprKind::Box(..)
96 | hir::ExprKind::Closure(.., _)
97 | hir::ExprKind::Unary(..)
98 | hir::ExprKind::Match(..) => Sugg::MaybeParen(snippet),
99 hir::ExprKind::Continue(..)
100 | hir::ExprKind::Yield(..)
101 | hir::ExprKind::Array(..)
102 | hir::ExprKind::Block(..)
103 | hir::ExprKind::Break(..)
104 | hir::ExprKind::Call(..)
105 | hir::ExprKind::Field(..)
106 | hir::ExprKind::Index(..)
107 | hir::ExprKind::InlineAsm(..)
108 | hir::ExprKind::Lit(..)
109 | hir::ExprKind::Loop(..)
110 | hir::ExprKind::MethodCall(..)
111 | hir::ExprKind::Path(..)
112 | hir::ExprKind::Repeat(..)
113 | hir::ExprKind::Ret(..)
114 | hir::ExprKind::Struct(..)
115 | hir::ExprKind::Tup(..)
116 | hir::ExprKind::DropTemps(_)
117 | hir::ExprKind::Err => Sugg::NonParen(snippet),
118 hir::ExprKind::Assign(..) => Sugg::BinOp(AssocOp::Assign, snippet),
119 hir::ExprKind::AssignOp(op, ..) => Sugg::BinOp(hirbinop2assignop(op), snippet),
120 hir::ExprKind::Binary(op, ..) => Sugg::BinOp(AssocOp::from_ast_binop(higher::binop(op.node)), snippet),
121 hir::ExprKind::Cast(..) => Sugg::BinOp(AssocOp::As, snippet),
122 hir::ExprKind::Type(..) => Sugg::BinOp(AssocOp::Colon, snippet),
126 /// Prepare a suggestion from an expression.
127 pub fn ast(cx: &EarlyContext<'_>, expr: &ast::Expr, default: &'a str) -> Self {
128 use syntax::ast::RangeLimits;
130 let snippet = snippet(cx, expr.span, default);
133 ast::ExprKind::AddrOf(..)
134 | ast::ExprKind::Box(..)
135 | ast::ExprKind::Closure(..)
136 | ast::ExprKind::If(..)
137 | ast::ExprKind::Let(..)
138 | ast::ExprKind::Unary(..)
139 | ast::ExprKind::Match(..) => Sugg::MaybeParen(snippet),
140 ast::ExprKind::Async(..)
141 | ast::ExprKind::Block(..)
142 | ast::ExprKind::Break(..)
143 | ast::ExprKind::Call(..)
144 | ast::ExprKind::Continue(..)
145 | ast::ExprKind::Yield(..)
146 | ast::ExprKind::Field(..)
147 | ast::ExprKind::ForLoop(..)
148 | ast::ExprKind::Index(..)
149 | ast::ExprKind::InlineAsm(..)
150 | ast::ExprKind::Lit(..)
151 | ast::ExprKind::Loop(..)
152 | ast::ExprKind::Mac(..)
153 | ast::ExprKind::MethodCall(..)
154 | ast::ExprKind::Paren(..)
155 | ast::ExprKind::Path(..)
156 | ast::ExprKind::Repeat(..)
157 | ast::ExprKind::Ret(..)
158 | ast::ExprKind::Struct(..)
159 | ast::ExprKind::Try(..)
160 | ast::ExprKind::TryBlock(..)
161 | ast::ExprKind::Tup(..)
162 | ast::ExprKind::Array(..)
163 | ast::ExprKind::While(..)
164 | ast::ExprKind::Await(..)
165 | ast::ExprKind::Err => Sugg::NonParen(snippet),
166 ast::ExprKind::Range(.., RangeLimits::HalfOpen) => Sugg::BinOp(AssocOp::DotDot, snippet),
167 ast::ExprKind::Range(.., RangeLimits::Closed) => Sugg::BinOp(AssocOp::DotDotEq, snippet),
168 ast::ExprKind::Assign(..) => Sugg::BinOp(AssocOp::Assign, snippet),
169 ast::ExprKind::AssignOp(op, ..) => Sugg::BinOp(astbinop2assignop(op), snippet),
170 ast::ExprKind::Binary(op, ..) => Sugg::BinOp(AssocOp::from_ast_binop(op.node), snippet),
171 ast::ExprKind::Cast(..) => Sugg::BinOp(AssocOp::As, snippet),
172 ast::ExprKind::Type(..) => Sugg::BinOp(AssocOp::Colon, snippet),
176 /// Convenience method to create the `<lhs> && <rhs>` suggestion.
177 pub fn and(self, rhs: &Self) -> Sugg<'static> {
178 make_binop(ast::BinOpKind::And, &self, rhs)
181 /// Convenience method to create the `<lhs> & <rhs>` suggestion.
182 pub fn bit_and(self, rhs: &Self) -> Sugg<'static> {
183 make_binop(ast::BinOpKind::BitAnd, &self, rhs)
186 /// Convenience method to create the `<lhs> as <rhs>` suggestion.
187 pub fn as_ty<R: Display>(self, rhs: R) -> Sugg<'static> {
188 make_assoc(AssocOp::As, &self, &Sugg::NonParen(rhs.to_string().into()))
191 /// Convenience method to create the `&<expr>` suggestion.
192 pub fn addr(self) -> Sugg<'static> {
196 /// Convenience method to create the `&mut <expr>` suggestion.
197 pub fn mut_addr(self) -> Sugg<'static> {
198 make_unop("&mut ", self)
201 /// Convenience method to create the `*<expr>` suggestion.
202 pub fn deref(self) -> Sugg<'static> {
206 /// Convenience method to create the `&*<expr>` suggestion. Currently this
207 /// is needed because `sugg.deref().addr()` produces an unnecessary set of
208 /// parentheses around the deref.
209 pub fn addr_deref(self) -> Sugg<'static> {
210 make_unop("&*", self)
213 /// Convenience method to create the `&mut *<expr>` suggestion. Currently
214 /// this is needed because `sugg.deref().mut_addr()` produces an unnecessary
215 /// set of parentheses around the deref.
216 pub fn mut_addr_deref(self) -> Sugg<'static> {
217 make_unop("&mut *", self)
220 /// Convenience method to transform suggestion into a return call
221 pub fn make_return(self) -> Sugg<'static> {
222 Sugg::NonParen(Cow::Owned(format!("return {}", self)))
225 /// Convenience method to transform suggestion into a block
226 /// where the suggestion is a trailing expression
227 pub fn blockify(self) -> Sugg<'static> {
228 Sugg::NonParen(Cow::Owned(format!("{{ {} }}", self)))
231 /// Convenience method to create the `<lhs>..<rhs>` or `<lhs>...<rhs>`
234 pub fn range(self, end: &Self, limit: ast::RangeLimits) -> Sugg<'static> {
236 ast::RangeLimits::HalfOpen => make_assoc(AssocOp::DotDot, &self, end),
237 ast::RangeLimits::Closed => make_assoc(AssocOp::DotDotEq, &self, end),
241 /// Adds parenthesis to any expression that might need them. Suitable to the
242 /// `self` argument of a method call
243 /// (e.g., to build `bar.foo()` or `(1 + 2).foo()`).
244 pub fn maybe_par(self) -> Self {
246 Sugg::NonParen(..) => self,
247 // `(x)` and `(x).y()` both don't need additional parens.
248 Sugg::MaybeParen(sugg) => {
249 if sugg.starts_with('(') && sugg.ends_with(')') {
250 Sugg::MaybeParen(sugg)
252 Sugg::NonParen(format!("({})", sugg).into())
255 Sugg::BinOp(_, sugg) => Sugg::NonParen(format!("({})", sugg).into()),
260 impl<'a, 'b> std::ops::Add<Sugg<'b>> for Sugg<'a> {
261 type Output = Sugg<'static>;
262 fn add(self, rhs: Sugg<'b>) -> Sugg<'static> {
263 make_binop(ast::BinOpKind::Add, &self, &rhs)
267 impl<'a, 'b> std::ops::Sub<Sugg<'b>> for Sugg<'a> {
268 type Output = Sugg<'static>;
269 fn sub(self, rhs: Sugg<'b>) -> Sugg<'static> {
270 make_binop(ast::BinOpKind::Sub, &self, &rhs)
274 impl<'a> std::ops::Not for Sugg<'a> {
275 type Output = Sugg<'static>;
276 fn not(self) -> Sugg<'static> {
281 /// Helper type to display either `foo` or `(foo)`.
282 struct ParenHelper<T> {
283 /// `true` if parentheses are needed.
285 /// The main thing to display.
289 impl<T> ParenHelper<T> {
290 /// Builds a `ParenHelper`.
291 fn new(paren: bool, wrapped: T) -> Self {
292 Self { paren, wrapped }
296 impl<T: Display> Display for ParenHelper<T> {
297 fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
299 write!(f, "({})", self.wrapped)
306 /// Builds the string for `<op><expr>` adding parenthesis when necessary.
308 /// For convenience, the operator is taken as a string because all unary
309 /// operators have the same
311 pub fn make_unop(op: &str, expr: Sugg<'_>) -> Sugg<'static> {
312 Sugg::MaybeParen(format!("{}{}", op, expr.maybe_par()).into())
315 /// Builds the string for `<lhs> <op> <rhs>` adding parenthesis when necessary.
317 /// Precedence of shift operator relative to other arithmetic operation is
318 /// often confusing so
319 /// parenthesis will always be added for a mix of these.
320 pub fn make_assoc(op: AssocOp, lhs: &Sugg<'_>, rhs: &Sugg<'_>) -> Sugg<'static> {
321 /// Returns `true` if the operator is a shift operator `<<` or `>>`.
322 fn is_shift(op: &AssocOp) -> bool {
323 matches!(*op, AssocOp::ShiftLeft | AssocOp::ShiftRight)
326 /// Returns `true` if the operator is a arithmetic operator
327 /// (i.e., `+`, `-`, `*`, `/`, `%`).
328 fn is_arith(op: &AssocOp) -> bool {
331 AssocOp::Add | AssocOp::Subtract | AssocOp::Multiply | AssocOp::Divide | AssocOp::Modulus
335 /// Returns `true` if the operator `op` needs parenthesis with the operator
336 /// `other` in the direction `dir`.
337 fn needs_paren(op: &AssocOp, other: &AssocOp, dir: Associativity) -> bool {
338 other.precedence() < op.precedence()
339 || (other.precedence() == op.precedence()
340 && ((op != other && associativity(op) != dir)
341 || (op == other && associativity(op) != Associativity::Both)))
342 || is_shift(op) && is_arith(other)
343 || is_shift(other) && is_arith(op)
346 let lhs_paren = if let Sugg::BinOp(ref lop, _) = *lhs {
347 needs_paren(&op, lop, Associativity::Left)
352 let rhs_paren = if let Sugg::BinOp(ref rop, _) = *rhs {
353 needs_paren(&op, rop, Associativity::Right)
358 let lhs = ParenHelper::new(lhs_paren, lhs);
359 let rhs = ParenHelper::new(rhs_paren, rhs);
360 let sugg = match op {
368 | AssocOp::GreaterEqual
377 | AssocOp::ShiftRight
378 | AssocOp::Subtract => format!(
381 op.to_ast_binop().expect("Those are AST ops").to_string(),
384 AssocOp::Assign => format!("{} = {}", lhs, rhs),
385 AssocOp::AssignOp(op) => format!("{} {}= {}", lhs, token_kind_to_string(&token::BinOp(op)), rhs),
386 AssocOp::As => format!("{} as {}", lhs, rhs),
387 AssocOp::DotDot => format!("{}..{}", lhs, rhs),
388 AssocOp::DotDotEq => format!("{}..={}", lhs, rhs),
389 AssocOp::Colon => format!("{}: {}", lhs, rhs),
392 Sugg::BinOp(op, sugg.into())
395 /// Convenience wrapper around `make_assoc` and `AssocOp::from_ast_binop`.
396 pub fn make_binop(op: ast::BinOpKind, lhs: &Sugg<'_>, rhs: &Sugg<'_>) -> Sugg<'static> {
397 make_assoc(AssocOp::from_ast_binop(op), lhs, rhs)
400 #[derive(PartialEq, Eq, Clone, Copy)]
401 /// Operator associativity.
403 /// The operator is both left-associative and right-associative.
405 /// The operator is left-associative.
407 /// The operator is not associative.
409 /// The operator is right-associative.
413 /// Returns the associativity/fixity of an operator. The difference with
414 /// `AssocOp::fixity` is that an operator can be both left and right associative
415 /// (such as `+`: `a + b + c == (a + b) + c == a + (b + c)`.
417 /// Chained `as` and explicit `:` type coercion never need inner parenthesis so
418 /// they are considered
420 fn associativity(op: &AssocOp) -> Associativity {
421 use syntax::util::parser::AssocOp::*;
424 Assign | AssignOp(_) => Associativity::Right,
425 Add | BitAnd | BitOr | BitXor | LAnd | LOr | Multiply | As | Colon => Associativity::Both,
426 Divide | Equal | Greater | GreaterEqual | Less | LessEqual | Modulus | NotEqual | ShiftLeft | ShiftRight
427 | Subtract => Associativity::Left,
428 DotDot | DotDotEq => Associativity::None,
432 /// Converts a `hir::BinOp` to the corresponding assigning binary operator.
433 fn hirbinop2assignop(op: hir::BinOp) -> AssocOp {
434 use syntax::parse::token::BinOpToken::*;
436 AssocOp::AssignOp(match op.node {
437 hir::BinOpKind::Add => Plus,
438 hir::BinOpKind::BitAnd => And,
439 hir::BinOpKind::BitOr => Or,
440 hir::BinOpKind::BitXor => Caret,
441 hir::BinOpKind::Div => Slash,
442 hir::BinOpKind::Mul => Star,
443 hir::BinOpKind::Rem => Percent,
444 hir::BinOpKind::Shl => Shl,
445 hir::BinOpKind::Shr => Shr,
446 hir::BinOpKind::Sub => Minus,
455 | hir::BinOpKind::Or => panic!("This operator does not exist"),
459 /// Converts an `ast::BinOp` to the corresponding assigning binary operator.
460 fn astbinop2assignop(op: ast::BinOp) -> AssocOp {
461 use syntax::ast::BinOpKind::*;
462 use syntax::parse::token::BinOpToken;
464 AssocOp::AssignOp(match op.node {
465 Add => BinOpToken::Plus,
466 BitAnd => BinOpToken::And,
467 BitOr => BinOpToken::Or,
468 BitXor => BinOpToken::Caret,
469 Div => BinOpToken::Slash,
470 Mul => BinOpToken::Star,
471 Rem => BinOpToken::Percent,
472 Shl => BinOpToken::Shl,
473 Shr => BinOpToken::Shr,
474 Sub => BinOpToken::Minus,
475 And | Eq | Ge | Gt | Le | Lt | Ne | Or => panic!("This operator does not exist"),
479 /// Returns the indentation before `span` if there are nothing but `[ \t]`
480 /// before it on its line.
481 fn indentation<T: LintContext>(cx: &T, span: Span) -> Option<String> {
482 let lo = cx.sess().source_map().lookup_char_pos(span.lo());
483 if let Some(line) = lo.file.get_line(lo.line - 1 /* line numbers in `Loc` are 1-based */) {
484 if let Some((pos, _)) = line.char_indices().find(|&(_, c)| c != ' ' && c != '\t') {
485 // We can mix char and byte positions here because we only consider `[ \t]`.
486 if lo.col == CharPos(pos) {
487 Some(line[..pos].into())
499 /// Convenience extension trait for `DiagnosticBuilder`.
500 pub trait DiagnosticBuilderExt<'a, T: LintContext> {
501 /// Suggests to add an attribute to an item.
503 /// Correctly handles indentation of the attribute and item.
508 /// db.suggest_item_with_attr(cx, item, "#[derive(Default)]");
510 fn suggest_item_with_attr<D: Display + ?Sized>(
516 applicability: Applicability,
519 /// Suggest to add an item before another.
521 /// The item should not be indented (expect for inner indentation).
526 /// db.suggest_prepend_item(cx, item,
531 fn suggest_prepend_item(&mut self, cx: &T, item: Span, msg: &str, new_item: &str, applicability: Applicability);
533 /// Suggest to completely remove an item.
535 /// This will remove an item and all following whitespace until the next non-whitespace
536 /// character. This should work correctly if item is on the same indentation level as the
542 /// db.suggest_remove_item(cx, item, "remove this")
544 fn suggest_remove_item(&mut self, cx: &T, item: Span, msg: &str, applicability: Applicability);
547 impl<'a, 'b, 'c, T: LintContext> DiagnosticBuilderExt<'c, T> for rustc_errors::DiagnosticBuilder<'b> {
548 fn suggest_item_with_attr<D: Display + ?Sized>(
554 applicability: Applicability,
556 if let Some(indent) = indentation(cx, item) {
557 let span = item.with_hi(item.lo());
559 self.span_suggestion(span, msg, format!("{}\n{}", attr, indent), applicability);
563 fn suggest_prepend_item(&mut self, cx: &T, item: Span, msg: &str, new_item: &str, applicability: Applicability) {
564 if let Some(indent) = indentation(cx, item) {
565 let span = item.with_hi(item.lo());
567 let mut first = true;
568 let new_item = new_item
575 format!("{}{}\n", indent, l)
578 .collect::<String>();
580 self.span_suggestion(span, msg, format!("{}\n{}", new_item, indent), applicability);
584 fn suggest_remove_item(&mut self, cx: &T, item: Span, msg: &str, applicability: Applicability) {
585 let mut remove_span = item;
586 let hi = cx.sess().source_map().next_point(remove_span).hi();
587 let fmpos = cx.sess().source_map().lookup_byte_offset(hi);
589 if let Some(ref src) = fmpos.sf.src {
590 let non_whitespace_offset = src[fmpos.pos.to_usize()..].find(|c| c != ' ' && c != '\t' && c != '\n');
592 if let Some(non_whitespace_offset) = non_whitespace_offset {
593 remove_span = remove_span
594 .with_hi(remove_span.hi() + BytePos(non_whitespace_offset.try_into().expect("offset too large")))
598 self.span_suggestion(remove_span, msg, String::new(), applicability);
605 use std::borrow::Cow;
607 const SUGGESTION: Sugg<'static> = Sugg::NonParen(Cow::Borrowed("function_call()"));
610 fn make_return_transform_sugg_into_a_return_call() {
611 assert_eq!("return function_call()", SUGGESTION.make_return().to_string());
615 fn blockify_transforms_sugg_into_a_block() {
616 assert_eq!("{ function_call() }", SUGGESTION.blockify().to_string());