1 //! Contains utility functions to generate suggestions.
2 #![deny(missing_docs_in_private_items)]
3 // currently ignores lifetimes and generics
7 use rustc::lint::{EarlyContext, LateContext, LintContext};
10 use std::fmt::Display;
12 use syntax::codemap::{CharPos, Span};
13 use syntax::parse::token;
14 use syntax::print::pprust::token_to_string;
15 use syntax::util::parser::AssocOp;
17 use utils::{higher, snippet, snippet_opt};
18 use syntax_pos::{BytePos, Pos};
20 /// A helper type to build suggestion correctly handling parenthesis.
22 /// An expression that never needs parenthesis such as `1337` or `[0; 42]`.
23 NonParen(Cow<'a, str>),
24 /// An expression that does not fit in other variants.
25 MaybeParen(Cow<'a, str>),
26 /// A binary operator expression, including `as`-casts and explicit type
28 BinOp(AssocOp, Cow<'a, str>),
31 /// Literal constant `1`, for convenience.
32 pub const ONE: Sugg<'static> = Sugg::NonParen(Cow::Borrowed("1"));
34 impl<'a> Display for Sugg<'a> {
35 fn fmt(&self, f: &mut std::fmt::Formatter) -> Result<(), std::fmt::Error> {
37 Sugg::NonParen(ref s) | Sugg::MaybeParen(ref s) | Sugg::BinOp(_, ref s) => s.fmt(f),
42 #[allow(wrong_self_convention)] // ok, because of the function `as_ty` method
44 /// Prepare a suggestion from an expression.
45 pub fn hir_opt(cx: &LateContext, expr: &hir::Expr) -> Option<Self> {
46 snippet_opt(cx, expr.span).map(|snippet| {
47 let snippet = Cow::Owned(snippet);
51 hir::ExprClosure(.., _) |
54 hir::ExprMatch(..) => Sugg::MaybeParen(snippet),
63 hir::ExprInlineAsm(..) |
66 hir::ExprMethodCall(..) |
72 hir::ExprWhile(..) => Sugg::NonParen(snippet),
73 hir::ExprAssign(..) => Sugg::BinOp(AssocOp::Assign, snippet),
74 hir::ExprAssignOp(op, ..) => Sugg::BinOp(hirbinop2assignop(op), snippet),
75 hir::ExprBinary(op, ..) => Sugg::BinOp(AssocOp::from_ast_binop(higher::binop(op.node)), snippet),
76 hir::ExprCast(..) => Sugg::BinOp(AssocOp::As, snippet),
77 hir::ExprType(..) => Sugg::BinOp(AssocOp::Colon, snippet),
82 /// Convenience function around `hir_opt` for suggestions with a default
84 pub fn hir(cx: &LateContext, expr: &hir::Expr, default: &'a str) -> Self {
85 Self::hir_opt(cx, expr).unwrap_or_else(|| Sugg::NonParen(Cow::Borrowed(default)))
88 /// Prepare a suggestion from an expression.
89 pub fn ast(cx: &EarlyContext, expr: &ast::Expr, default: &'a str) -> Self {
90 use syntax::ast::RangeLimits;
92 let snippet = snippet(cx, expr.span, default);
95 ast::ExprKind::AddrOf(..) |
96 ast::ExprKind::Box(..) |
97 ast::ExprKind::Closure(..) |
98 ast::ExprKind::If(..) |
99 ast::ExprKind::IfLet(..) |
100 ast::ExprKind::Unary(..) |
101 ast::ExprKind::Match(..) => Sugg::MaybeParen(snippet),
102 ast::ExprKind::Block(..) |
103 ast::ExprKind::Break(..) |
104 ast::ExprKind::Call(..) |
105 ast::ExprKind::Catch(..) |
106 ast::ExprKind::Continue(..) |
107 ast::ExprKind::Yield(..) |
108 ast::ExprKind::Field(..) |
109 ast::ExprKind::ForLoop(..) |
110 ast::ExprKind::Index(..) |
111 ast::ExprKind::InlineAsm(..) |
112 ast::ExprKind::Lit(..) |
113 ast::ExprKind::Loop(..) |
114 ast::ExprKind::Mac(..) |
115 ast::ExprKind::MethodCall(..) |
116 ast::ExprKind::Paren(..) |
117 ast::ExprKind::Path(..) |
118 ast::ExprKind::Repeat(..) |
119 ast::ExprKind::Ret(..) |
120 ast::ExprKind::Struct(..) |
121 ast::ExprKind::Try(..) |
122 ast::ExprKind::Tup(..) |
123 ast::ExprKind::Array(..) |
124 ast::ExprKind::While(..) |
125 ast::ExprKind::WhileLet(..) => Sugg::NonParen(snippet),
126 ast::ExprKind::Range(.., RangeLimits::HalfOpen) => Sugg::BinOp(AssocOp::DotDot, snippet),
127 ast::ExprKind::Range(.., RangeLimits::Closed) => Sugg::BinOp(AssocOp::DotDotEq, snippet),
128 ast::ExprKind::Assign(..) => Sugg::BinOp(AssocOp::Assign, snippet),
129 ast::ExprKind::AssignOp(op, ..) => Sugg::BinOp(astbinop2assignop(op), snippet),
130 ast::ExprKind::Binary(op, ..) => Sugg::BinOp(AssocOp::from_ast_binop(op.node), snippet),
131 ast::ExprKind::Cast(..) => Sugg::BinOp(AssocOp::As, snippet),
132 ast::ExprKind::Type(..) => Sugg::BinOp(AssocOp::Colon, snippet),
136 /// Convenience method to create the `<lhs> && <rhs>` suggestion.
137 pub fn and(self, rhs: &Self) -> Sugg<'static> {
138 make_binop(ast::BinOpKind::And, &self, rhs)
141 /// Convenience method to create the `<lhs> as <rhs>` suggestion.
142 pub fn as_ty<R: Display>(self, rhs: R) -> Sugg<'static> {
143 make_assoc(AssocOp::As, &self, &Sugg::NonParen(rhs.to_string().into()))
146 /// Convenience method to create the `&<expr>` suggestion.
147 pub fn addr(self) -> Sugg<'static> {
151 /// Convenience method to create the `&mut <expr>` suggestion.
152 pub fn mut_addr(self) -> Sugg<'static> {
153 make_unop("&mut ", self)
156 /// Convenience method to create the `*<expr>` suggestion.
157 pub fn deref(self) -> Sugg<'static> {
161 /// Convenience method to create the `&*<expr>` suggestion. Currently this
162 /// is needed because `sugg.deref().addr()` produces an unnecessary set of
163 /// parentheses around the deref.
164 pub fn addr_deref(self) -> Sugg<'static> {
165 make_unop("&*", self)
168 /// Convenience method to create the `&mut *<expr>` suggestion. Currently
169 /// this is needed because `sugg.deref().mut_addr()` produces an unnecessary
170 /// set of parentheses around the deref.
171 pub fn mut_addr_deref(self) -> Sugg<'static> {
172 make_unop("&mut *", self)
175 /// Convenience method to create the `<lhs>..<rhs>` or `<lhs>...<rhs>`
177 pub fn range(self, end: &Self, limit: ast::RangeLimits) -> Sugg<'static> {
179 ast::RangeLimits::HalfOpen => make_assoc(AssocOp::DotDot, &self, end),
180 ast::RangeLimits::Closed => make_assoc(AssocOp::DotDotEq, &self, end),
184 /// Add parenthesis to any expression that might need them. Suitable to the
185 /// `self` argument of
186 /// a method call (eg. to build `bar.foo()` or `(1 + 2).foo()`).
187 pub fn maybe_par(self) -> Self {
189 Sugg::NonParen(..) => self,
190 // (x) and (x).y() both don't need additional parens
191 Sugg::MaybeParen(sugg) => if sugg.starts_with('(') && sugg.ends_with(')') {
192 Sugg::MaybeParen(sugg)
194 Sugg::NonParen(format!("({})", sugg).into())
196 Sugg::BinOp(_, sugg) => Sugg::NonParen(format!("({})", sugg).into()),
201 impl<'a, 'b> std::ops::Add<Sugg<'b>> for Sugg<'a> {
202 type Output = Sugg<'static>;
203 fn add(self, rhs: Sugg<'b>) -> Sugg<'static> {
204 make_binop(ast::BinOpKind::Add, &self, &rhs)
208 impl<'a, 'b> std::ops::Sub<Sugg<'b>> for Sugg<'a> {
209 type Output = Sugg<'static>;
210 fn sub(self, rhs: Sugg<'b>) -> Sugg<'static> {
211 make_binop(ast::BinOpKind::Sub, &self, &rhs)
215 impl<'a> std::ops::Not for Sugg<'a> {
216 type Output = Sugg<'static>;
217 fn not(self) -> Sugg<'static> {
222 /// Helper type to display either `foo` or `(foo)`.
223 struct ParenHelper<T> {
224 /// Whether parenthesis are needed.
226 /// The main thing to display.
230 impl<T> ParenHelper<T> {
231 /// Build a `ParenHelper`.
232 fn new(paren: bool, wrapped: T) -> Self {
240 impl<T: Display> Display for ParenHelper<T> {
241 fn fmt(&self, f: &mut std::fmt::Formatter) -> Result<(), std::fmt::Error> {
243 write!(f, "({})", self.wrapped)
250 /// Build the string for `<op><expr>` adding parenthesis when necessary.
252 /// For convenience, the operator is taken as a string because all unary
253 /// operators have the same
255 pub fn make_unop(op: &str, expr: Sugg) -> Sugg<'static> {
256 Sugg::MaybeParen(format!("{}{}", op, expr.maybe_par()).into())
259 /// Build the string for `<lhs> <op> <rhs>` adding parenthesis when necessary.
261 /// Precedence of shift operator relative to other arithmetic operation is
262 /// often confusing so
263 /// parenthesis will always be added for a mix of these.
264 pub fn make_assoc(op: AssocOp, lhs: &Sugg, rhs: &Sugg) -> Sugg<'static> {
265 /// Whether the operator is a shift operator `<<` or `>>`.
266 fn is_shift(op: &AssocOp) -> bool {
267 matches!(*op, AssocOp::ShiftLeft | AssocOp::ShiftRight)
270 /// Whether the operator is a arithmetic operator (`+`, `-`, `*`, `/`, `%`).
271 fn is_arith(op: &AssocOp) -> bool {
274 AssocOp::Add | AssocOp::Subtract | AssocOp::Multiply | AssocOp::Divide | AssocOp::Modulus
278 /// Whether the operator `op` needs parenthesis with the operator `other`
281 fn needs_paren(op: &AssocOp, other: &AssocOp, dir: Associativity) -> bool {
282 other.precedence() < op.precedence()
283 || (other.precedence() == op.precedence()
284 && ((op != other && associativity(op) != dir)
285 || (op == other && associativity(op) != Associativity::Both)))
286 || is_shift(op) && is_arith(other) || is_shift(other) && is_arith(op)
289 let lhs_paren = if let Sugg::BinOp(ref lop, _) = *lhs {
290 needs_paren(&op, lop, Associativity::Left)
295 let rhs_paren = if let Sugg::BinOp(ref rop, _) = *rhs {
296 needs_paren(&op, rop, Associativity::Right)
301 let lhs = ParenHelper::new(lhs_paren, lhs);
302 let rhs = ParenHelper::new(rhs_paren, rhs);
303 let sugg = match op {
311 AssocOp::GreaterEqual |
320 AssocOp::ShiftRight |
321 AssocOp::Subtract => format!("{} {} {}", lhs, op.to_ast_binop().expect("Those are AST ops").to_string(), rhs),
322 AssocOp::Assign => format!("{} = {}", lhs, rhs),
323 AssocOp::AssignOp(op) => format!("{} {}= {}", lhs, token_to_string(&token::BinOp(op)), rhs),
324 AssocOp::As => format!("{} as {}", lhs, rhs),
325 AssocOp::DotDot => format!("{}..{}", lhs, rhs),
326 AssocOp::DotDotEq => format!("{}..={}", lhs, rhs),
327 AssocOp::Colon => format!("{}: {}", lhs, rhs),
330 Sugg::BinOp(op, sugg.into())
333 /// Convinience wrapper arround `make_assoc` and `AssocOp::from_ast_binop`.
334 pub fn make_binop(op: ast::BinOpKind, lhs: &Sugg, rhs: &Sugg) -> Sugg<'static> {
335 make_assoc(AssocOp::from_ast_binop(op), lhs, rhs)
338 #[derive(PartialEq, Eq, Clone, Copy)]
339 /// Operator associativity.
341 /// The operator is both left-associative and right-associative.
343 /// The operator is left-associative.
345 /// The operator is not associative.
347 /// The operator is right-associative.
351 /// Return the associativity/fixity of an operator. The difference with
352 /// `AssocOp::fixity` is that
353 /// an operator can be both left and right associative (such as `+`:
354 /// `a + b + c == (a + b) + c == a + (b + c)`.
356 /// Chained `as` and explicit `:` type coercion never need inner parenthesis so
357 /// they are considered
359 fn associativity(op: &AssocOp) -> Associativity {
360 use syntax::util::parser::AssocOp::*;
363 Assign | AssignOp(_) => Associativity::Right,
364 Add | BitAnd | BitOr | BitXor | LAnd | LOr | Multiply | As | Colon => Associativity::Both,
375 Subtract => Associativity::Left,
376 DotDot | DotDotEq => Associativity::None,
380 /// Convert a `hir::BinOp` to the corresponding assigning binary operator.
381 fn hirbinop2assignop(op: hir::BinOp) -> AssocOp {
382 use rustc::hir::BinOp_::*;
383 use syntax::parse::token::BinOpToken::*;
385 AssocOp::AssignOp(match op.node {
396 BiAnd | BiEq | BiGe | BiGt | BiLe | BiLt | BiNe | BiOr => panic!("This operator does not exist"),
400 /// Convert an `ast::BinOp` to the corresponding assigning binary operator.
401 fn astbinop2assignop(op: ast::BinOp) -> AssocOp {
402 use syntax::ast::BinOpKind::*;
403 use syntax::parse::token::BinOpToken;
405 AssocOp::AssignOp(match op.node {
406 Add => BinOpToken::Plus,
407 BitAnd => BinOpToken::And,
408 BitOr => BinOpToken::Or,
409 BitXor => BinOpToken::Caret,
410 Div => BinOpToken::Slash,
411 Mul => BinOpToken::Star,
412 Rem => BinOpToken::Percent,
413 Shl => BinOpToken::Shl,
414 Shr => BinOpToken::Shr,
415 Sub => BinOpToken::Minus,
416 And | Eq | Ge | Gt | Le | Lt | Ne | Or => panic!("This operator does not exist"),
420 /// Return the indentation before `span` if there are nothing but `[ \t]`
421 /// before it on its line.
422 fn indentation<'a, T: LintContext<'a>>(cx: &T, span: Span) -> Option<String> {
423 let lo = cx.sess().codemap().lookup_char_pos(span.lo());
424 if let Some(line) = lo.file
425 .get_line(lo.line - 1 /* line numbers in `Loc` are 1-based */)
427 if let Some((pos, _)) = line.char_indices().find(|&(_, c)| c != ' ' && c != '\t') {
428 // we can mix char and byte positions here because we only consider `[ \t]`
429 if lo.col == CharPos(pos) {
430 Some(line[..pos].into())
442 /// Convenience extension trait for `DiagnosticBuilder`.
443 pub trait DiagnosticBuilderExt<'a, T: LintContext<'a>> {
444 /// Suggests to add an attribute to an item.
446 /// Correctly handles indentation of the attribute and item.
451 /// db.suggest_item_with_attr(cx, item, "#[derive(Default)]");
453 fn suggest_item_with_attr<D: Display + ?Sized>(&mut self, cx: &T, item: Span, msg: &str, attr: &D);
455 /// Suggest to add an item before another.
457 /// The item should not be indented (expect for inner indentation).
462 /// db.suggest_prepend_item(cx, item,
467 fn suggest_prepend_item(&mut self, cx: &T, item: Span, msg: &str, new_item: &str);
469 /// Suggest to completely remove an item.
471 /// This will remove an item and all following whitespace until the next non-whitespace
472 /// character. This should work correctly if item is on the same indentation level as the
478 /// db.suggest_remove_item(cx, item, "remove this")
480 fn suggest_remove_item(&mut self, cx: &T, item: Span, msg: &str);
483 impl<'a, 'b, 'c, T: LintContext<'c>> DiagnosticBuilderExt<'c, T> for rustc_errors::DiagnosticBuilder<'b> {
484 fn suggest_item_with_attr<D: Display + ?Sized>(&mut self, cx: &T, item: Span, msg: &str, attr: &D) {
485 if let Some(indent) = indentation(cx, item) {
486 let span = item.with_hi(item.lo());
488 self.span_suggestion(span, msg, format!("{}\n{}", attr, indent));
492 fn suggest_prepend_item(&mut self, cx: &T, item: Span, msg: &str, new_item: &str) {
493 if let Some(indent) = indentation(cx, item) {
494 let span = item.with_hi(item.lo());
496 let mut first = true;
497 let new_item = new_item
504 format!("{}{}\n", indent, l)
507 .collect::<String>();
509 self.span_suggestion(span, msg, format!("{}\n{}", new_item, indent));
513 fn suggest_remove_item(&mut self, cx: &T, item: Span, msg: &str) {
514 let mut remove_span = item;
515 let hi = cx.sess().codemap().next_point(remove_span).hi();
516 let fmpos = cx.sess().codemap().lookup_byte_offset(hi);
518 if let Some(ref src) = fmpos.fm.src {
519 let non_whitespace_offset = src[fmpos.pos.to_usize()..].find(|c| c != ' ' && c != '\t' && c != '\n');
521 if let Some(non_whitespace_offset) = non_whitespace_offset {
522 remove_span = remove_span.with_hi(remove_span.hi() + BytePos(non_whitespace_offset as u32))
526 self.span_suggestion(remove_span, msg, String::new());