1 //! Contains utility functions to generate suggestions.
2 #![deny(missing_docs_in_private_items)]
3 // currently ignores lifetimes and generics
8 use rustc::lint::{EarlyContext, LateContext, LintContext};
11 use std::fmt::Display;
13 use syntax::source_map::{CharPos, Span};
14 use syntax::parse::token;
15 use syntax::print::pprust::token_to_string;
16 use syntax::util::parser::AssocOp;
18 use crate::utils::{higher, snippet, snippet_opt};
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(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(..) => Sugg::NonParen(snippet),
74 hir::ExprKind::Assign(..) => Sugg::BinOp(AssocOp::Assign, snippet),
75 hir::ExprKind::AssignOp(op, ..) => Sugg::BinOp(hirbinop2assignop(op), snippet),
76 hir::ExprKind::Binary(op, ..) => Sugg::BinOp(AssocOp::from_ast_binop(higher::binop(op.node)), snippet),
77 hir::ExprKind::Cast(..) => Sugg::BinOp(AssocOp::As, snippet),
78 hir::ExprKind::Type(..) => Sugg::BinOp(AssocOp::Colon, snippet),
83 /// Convenience function around `hir_opt` for suggestions with a default
85 pub fn hir(cx: &LateContext<'_, '_>, expr: &hir::Expr, default: &'a str) -> Self {
86 Self::hir_opt(cx, expr).unwrap_or_else(|| Sugg::NonParen(Cow::Borrowed(default)))
89 /// Prepare a suggestion from an expression.
90 pub fn ast(cx: &EarlyContext<'_>, expr: &ast::Expr, default: &'a str) -> Self {
91 use syntax::ast::RangeLimits;
93 let snippet = snippet(cx, expr.span, default);
96 ast::ExprKind::AddrOf(..) |
97 ast::ExprKind::Box(..) |
98 ast::ExprKind::Closure(..) |
99 ast::ExprKind::If(..) |
100 ast::ExprKind::IfLet(..) |
101 ast::ExprKind::ObsoleteInPlace(..) |
102 ast::ExprKind::Unary(..) |
103 ast::ExprKind::Match(..) => Sugg::MaybeParen(snippet),
104 ast::ExprKind::Async(..) |
105 ast::ExprKind::Block(..) |
106 ast::ExprKind::Break(..) |
107 ast::ExprKind::Call(..) |
108 ast::ExprKind::Continue(..) |
109 ast::ExprKind::Yield(..) |
110 ast::ExprKind::Field(..) |
111 ast::ExprKind::ForLoop(..) |
112 ast::ExprKind::Index(..) |
113 ast::ExprKind::InlineAsm(..) |
114 ast::ExprKind::Lit(..) |
115 ast::ExprKind::Loop(..) |
116 ast::ExprKind::Mac(..) |
117 ast::ExprKind::MethodCall(..) |
118 ast::ExprKind::Paren(..) |
119 ast::ExprKind::Path(..) |
120 ast::ExprKind::Repeat(..) |
121 ast::ExprKind::Ret(..) |
122 ast::ExprKind::Struct(..) |
123 ast::ExprKind::Try(..) |
124 ast::ExprKind::TryBlock(..) |
125 ast::ExprKind::Tup(..) |
126 ast::ExprKind::Array(..) |
127 ast::ExprKind::While(..) |
128 ast::ExprKind::WhileLet(..) => Sugg::NonParen(snippet),
129 ast::ExprKind::Range(.., RangeLimits::HalfOpen) => Sugg::BinOp(AssocOp::DotDot, snippet),
130 ast::ExprKind::Range(.., RangeLimits::Closed) => Sugg::BinOp(AssocOp::DotDotEq, snippet),
131 ast::ExprKind::Assign(..) => Sugg::BinOp(AssocOp::Assign, snippet),
132 ast::ExprKind::AssignOp(op, ..) => Sugg::BinOp(astbinop2assignop(op), snippet),
133 ast::ExprKind::Binary(op, ..) => Sugg::BinOp(AssocOp::from_ast_binop(op.node), snippet),
134 ast::ExprKind::Cast(..) => Sugg::BinOp(AssocOp::As, snippet),
135 ast::ExprKind::Type(..) => Sugg::BinOp(AssocOp::Colon, snippet),
139 /// Convenience method to create the `<lhs> && <rhs>` suggestion.
140 pub fn and(self, rhs: &Self) -> Sugg<'static> {
141 make_binop(ast::BinOpKind::And, &self, rhs)
144 /// Convenience method to create the `<lhs> as <rhs>` suggestion.
145 pub fn as_ty<R: Display>(self, rhs: R) -> Sugg<'static> {
146 make_assoc(AssocOp::As, &self, &Sugg::NonParen(rhs.to_string().into()))
149 /// Convenience method to create the `&<expr>` suggestion.
150 pub fn addr(self) -> Sugg<'static> {
154 /// Convenience method to create the `&mut <expr>` suggestion.
155 pub fn mut_addr(self) -> Sugg<'static> {
156 make_unop("&mut ", self)
159 /// Convenience method to create the `*<expr>` suggestion.
160 pub fn deref(self) -> Sugg<'static> {
164 /// Convenience method to create the `&*<expr>` suggestion. Currently this
165 /// is needed because `sugg.deref().addr()` produces an unnecessary set of
166 /// parentheses around the deref.
167 pub fn addr_deref(self) -> Sugg<'static> {
168 make_unop("&*", self)
171 /// Convenience method to create the `&mut *<expr>` suggestion. Currently
172 /// this is needed because `sugg.deref().mut_addr()` produces an unnecessary
173 /// set of parentheses around the deref.
174 pub fn mut_addr_deref(self) -> Sugg<'static> {
175 make_unop("&mut *", self)
178 /// Convenience method to create the `<lhs>..<rhs>` or `<lhs>...<rhs>`
181 pub fn range(self, end: &Self, limit: ast::RangeLimits) -> Sugg<'static> {
183 ast::RangeLimits::HalfOpen => make_assoc(AssocOp::DotDot, &self, end),
184 ast::RangeLimits::Closed => make_assoc(AssocOp::DotDotEq, &self, end),
188 /// Add parenthesis to any expression that might need them. Suitable to the
189 /// `self` argument of
190 /// a method call (eg. to build `bar.foo()` or `(1 + 2).foo()`).
191 pub fn maybe_par(self) -> Self {
193 Sugg::NonParen(..) => self,
194 // (x) and (x).y() both don't need additional parens
195 Sugg::MaybeParen(sugg) => if sugg.starts_with('(') && sugg.ends_with(')') {
196 Sugg::MaybeParen(sugg)
198 Sugg::NonParen(format!("({})", sugg).into())
200 Sugg::BinOp(_, sugg) => Sugg::NonParen(format!("({})", sugg).into()),
205 impl<'a, 'b> std::ops::Add<Sugg<'b>> for Sugg<'a> {
206 type Output = Sugg<'static>;
207 fn add(self, rhs: Sugg<'b>) -> Sugg<'static> {
208 make_binop(ast::BinOpKind::Add, &self, &rhs)
212 impl<'a, 'b> std::ops::Sub<Sugg<'b>> for Sugg<'a> {
213 type Output = Sugg<'static>;
214 fn sub(self, rhs: Sugg<'b>) -> Sugg<'static> {
215 make_binop(ast::BinOpKind::Sub, &self, &rhs)
219 impl<'a> std::ops::Not for Sugg<'a> {
220 type Output = Sugg<'static>;
221 fn not(self) -> Sugg<'static> {
226 /// Helper type to display either `foo` or `(foo)`.
227 struct ParenHelper<T> {
228 /// Whether parenthesis are needed.
230 /// The main thing to display.
234 impl<T> ParenHelper<T> {
235 /// Build a `ParenHelper`.
236 fn new(paren: bool, wrapped: T) -> Self {
244 impl<T: Display> Display for ParenHelper<T> {
245 fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
247 write!(f, "({})", self.wrapped)
254 /// Build the string for `<op><expr>` adding parenthesis when necessary.
256 /// For convenience, the operator is taken as a string because all unary
257 /// operators have the same
259 pub fn make_unop(op: &str, expr: Sugg<'_>) -> Sugg<'static> {
260 Sugg::MaybeParen(format!("{}{}", op, expr.maybe_par()).into())
263 /// Build the string for `<lhs> <op> <rhs>` adding parenthesis when necessary.
265 /// Precedence of shift operator relative to other arithmetic operation is
266 /// often confusing so
267 /// parenthesis will always be added for a mix of these.
268 pub fn make_assoc(op: AssocOp, lhs: &Sugg<'_>, rhs: &Sugg<'_>) -> Sugg<'static> {
269 /// Whether the operator is a shift operator `<<` or `>>`.
270 fn is_shift(op: &AssocOp) -> bool {
271 matches!(*op, AssocOp::ShiftLeft | AssocOp::ShiftRight)
274 /// Whether the operator is a arithmetic operator (`+`, `-`, `*`, `/`, `%`).
275 fn is_arith(op: &AssocOp) -> bool {
278 AssocOp::Add | AssocOp::Subtract | AssocOp::Multiply | AssocOp::Divide | AssocOp::Modulus
282 /// Whether the operator `op` needs parenthesis with the operator `other`
285 fn needs_paren(op: &AssocOp, other: &AssocOp, dir: Associativity) -> bool {
286 other.precedence() < op.precedence()
287 || (other.precedence() == op.precedence()
288 && ((op != other && associativity(op) != dir)
289 || (op == other && associativity(op) != Associativity::Both)))
290 || is_shift(op) && is_arith(other) || is_shift(other) && is_arith(op)
293 let lhs_paren = if let Sugg::BinOp(ref lop, _) = *lhs {
294 needs_paren(&op, lop, Associativity::Left)
299 let rhs_paren = if let Sugg::BinOp(ref rop, _) = *rhs {
300 needs_paren(&op, rop, Associativity::Right)
305 let lhs = ParenHelper::new(lhs_paren, lhs);
306 let rhs = ParenHelper::new(rhs_paren, rhs);
307 let sugg = match op {
315 AssocOp::GreaterEqual |
324 AssocOp::ShiftRight |
325 AssocOp::Subtract => format!("{} {} {}", lhs, op.to_ast_binop().expect("Those are AST ops").to_string(), rhs),
326 AssocOp::Assign => format!("{} = {}", lhs, rhs),
327 AssocOp::ObsoleteInPlace => format!("in ({}) {}", lhs, rhs),
328 AssocOp::AssignOp(op) => format!("{} {}= {}", lhs, token_to_string(&token::BinOp(op)), rhs),
329 AssocOp::As => format!("{} as {}", lhs, rhs),
330 AssocOp::DotDot => format!("{}..{}", lhs, rhs),
331 AssocOp::DotDotEq => format!("{}..={}", lhs, rhs),
332 AssocOp::Colon => format!("{}: {}", lhs, rhs),
335 Sugg::BinOp(op, sugg.into())
338 /// Convenience wrapper around `make_assoc` and `AssocOp::from_ast_binop`.
339 pub fn make_binop(op: ast::BinOpKind, lhs: &Sugg<'_>, rhs: &Sugg<'_>) -> Sugg<'static> {
340 make_assoc(AssocOp::from_ast_binop(op), lhs, rhs)
343 #[derive(PartialEq, Eq, Clone, Copy)]
344 /// Operator associativity.
346 /// The operator is both left-associative and right-associative.
348 /// The operator is left-associative.
350 /// The operator is not associative.
352 /// The operator is right-associative.
356 /// Return the associativity/fixity of an operator. The difference with
357 /// `AssocOp::fixity` is that
358 /// an operator can be both left and right associative (such as `+`:
359 /// `a + b + c == (a + b) + c == a + (b + c)`.
361 /// Chained `as` and explicit `:` type coercion never need inner parenthesis so
362 /// they are considered
364 fn associativity(op: &AssocOp) -> Associativity {
365 use syntax::util::parser::AssocOp::*;
368 ObsoleteInPlace | Assign | AssignOp(_) => Associativity::Right,
369 Add | BitAnd | BitOr | BitXor | LAnd | LOr | Multiply | As | Colon => Associativity::Both,
380 Subtract => Associativity::Left,
381 DotDot | DotDotEq => Associativity::None,
385 /// Convert a `hir::BinOp` to the corresponding assigning binary operator.
386 fn hirbinop2assignop(op: hir::BinOp) -> AssocOp {
387 use syntax::parse::token::BinOpToken::*;
389 AssocOp::AssignOp(match op.node {
390 hir::BinOpKind::Add => Plus,
391 hir::BinOpKind::BitAnd => And,
392 hir::BinOpKind::BitOr => Or,
393 hir::BinOpKind::BitXor => Caret,
394 hir::BinOpKind::Div => Slash,
395 hir::BinOpKind::Mul => Star,
396 hir::BinOpKind::Rem => Percent,
397 hir::BinOpKind::Shl => Shl,
398 hir::BinOpKind::Shr => Shr,
399 hir::BinOpKind::Sub => Minus,
401 | hir::BinOpKind::And
409 => panic!("This operator does not exist"),
413 /// Convert an `ast::BinOp` to the corresponding assigning binary operator.
414 fn astbinop2assignop(op: ast::BinOp) -> AssocOp {
415 use syntax::ast::BinOpKind::*;
416 use syntax::parse::token::BinOpToken;
418 AssocOp::AssignOp(match op.node {
419 Add => BinOpToken::Plus,
420 BitAnd => BinOpToken::And,
421 BitOr => BinOpToken::Or,
422 BitXor => BinOpToken::Caret,
423 Div => BinOpToken::Slash,
424 Mul => BinOpToken::Star,
425 Rem => BinOpToken::Percent,
426 Shl => BinOpToken::Shl,
427 Shr => BinOpToken::Shr,
428 Sub => BinOpToken::Minus,
429 And | Eq | Ge | Gt | Le | Lt | Ne | Or => panic!("This operator does not exist"),
433 /// Return the indentation before `span` if there are nothing but `[ \t]`
434 /// before it on its line.
435 fn indentation<'a, T: LintContext<'a>>(cx: &T, span: Span) -> Option<String> {
436 let lo = cx.sess().source_map().lookup_char_pos(span.lo());
437 if let Some(line) = lo.file
438 .get_line(lo.line - 1 /* line numbers in `Loc` are 1-based */)
440 if let Some((pos, _)) = line.char_indices().find(|&(_, c)| c != ' ' && c != '\t') {
441 // we can mix char and byte positions here because we only consider `[ \t]`
442 if lo.col == CharPos(pos) {
443 Some(line[..pos].into())
455 /// Convenience extension trait for `DiagnosticBuilder`.
456 pub trait DiagnosticBuilderExt<'a, T: LintContext<'a>> {
457 /// Suggests to add an attribute to an item.
459 /// Correctly handles indentation of the attribute and item.
464 /// db.suggest_item_with_attr(cx, item, "#[derive(Default)]");
466 fn suggest_item_with_attr<D: Display + ?Sized>(&mut self, cx: &T, item: Span, msg: &str, attr: &D);
468 /// Suggest to add an item before another.
470 /// The item should not be indented (expect for inner indentation).
475 /// db.suggest_prepend_item(cx, item,
480 fn suggest_prepend_item(&mut self, cx: &T, item: Span, msg: &str, new_item: &str);
482 /// Suggest to completely remove an item.
484 /// This will remove an item and all following whitespace until the next non-whitespace
485 /// character. This should work correctly if item is on the same indentation level as the
491 /// db.suggest_remove_item(cx, item, "remove this")
493 fn suggest_remove_item(&mut self, cx: &T, item: Span, msg: &str);
496 impl<'a, 'b, 'c, T: LintContext<'c>> DiagnosticBuilderExt<'c, T> for rustc_errors::DiagnosticBuilder<'b> {
497 fn suggest_item_with_attr<D: Display + ?Sized>(&mut self, cx: &T, item: Span, msg: &str, attr: &D) {
498 if let Some(indent) = indentation(cx, item) {
499 let span = item.with_hi(item.lo());
501 self.span_suggestion(span, msg, format!("{}\n{}", attr, indent));
505 fn suggest_prepend_item(&mut self, cx: &T, item: Span, msg: &str, new_item: &str) {
506 if let Some(indent) = indentation(cx, item) {
507 let span = item.with_hi(item.lo());
509 let mut first = true;
510 let new_item = new_item
517 format!("{}{}\n", indent, l)
520 .collect::<String>();
522 self.span_suggestion(span, msg, format!("{}\n{}", new_item, indent));
526 fn suggest_remove_item(&mut self, cx: &T, item: Span, msg: &str) {
527 let mut remove_span = item;
528 let hi = cx.sess().source_map().next_point(remove_span).hi();
529 let fmpos = cx.sess().source_map().lookup_byte_offset(hi);
531 if let Some(ref src) = fmpos.fm.src {
532 let non_whitespace_offset = src[fmpos.pos.to_usize()..].find(|c| c != ' ' && c != '\t' && c != '\n');
534 if let Some(non_whitespace_offset) = non_whitespace_offset {
535 remove_span = remove_span.with_hi(remove_span.hi() + BytePos(non_whitespace_offset as u32))
539 self.span_suggestion(remove_span, msg, String::new());