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 crate::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::ObsoleteInPlace(..) |
101 ast::ExprKind::Unary(..) |
102 ast::ExprKind::Match(..) => Sugg::MaybeParen(snippet),
103 ast::ExprKind::Block(..) |
104 ast::ExprKind::Break(..) |
105 ast::ExprKind::Call(..) |
106 ast::ExprKind::Catch(..) |
107 ast::ExprKind::Continue(..) |
108 ast::ExprKind::Yield(..) |
109 ast::ExprKind::Field(..) |
110 ast::ExprKind::ForLoop(..) |
111 ast::ExprKind::Index(..) |
112 ast::ExprKind::InlineAsm(..) |
113 ast::ExprKind::Lit(..) |
114 ast::ExprKind::Loop(..) |
115 ast::ExprKind::Mac(..) |
116 ast::ExprKind::MethodCall(..) |
117 ast::ExprKind::Paren(..) |
118 ast::ExprKind::Path(..) |
119 ast::ExprKind::Repeat(..) |
120 ast::ExprKind::Ret(..) |
121 ast::ExprKind::Struct(..) |
122 ast::ExprKind::Try(..) |
123 ast::ExprKind::Tup(..) |
124 ast::ExprKind::Array(..) |
125 ast::ExprKind::While(..) |
126 ast::ExprKind::WhileLet(..) => Sugg::NonParen(snippet),
127 ast::ExprKind::Range(.., RangeLimits::HalfOpen) => Sugg::BinOp(AssocOp::DotDot, snippet),
128 ast::ExprKind::Range(.., RangeLimits::Closed) => Sugg::BinOp(AssocOp::DotDotEq, snippet),
129 ast::ExprKind::Assign(..) => Sugg::BinOp(AssocOp::Assign, snippet),
130 ast::ExprKind::AssignOp(op, ..) => Sugg::BinOp(astbinop2assignop(op), snippet),
131 ast::ExprKind::Binary(op, ..) => Sugg::BinOp(AssocOp::from_ast_binop(op.node), snippet),
132 ast::ExprKind::Cast(..) => Sugg::BinOp(AssocOp::As, snippet),
133 ast::ExprKind::Type(..) => Sugg::BinOp(AssocOp::Colon, snippet),
137 /// Convenience method to create the `<lhs> && <rhs>` suggestion.
138 pub fn and(self, rhs: &Self) -> Sugg<'static> {
139 make_binop(ast::BinOpKind::And, &self, rhs)
142 /// Convenience method to create the `<lhs> as <rhs>` suggestion.
143 pub fn as_ty<R: Display>(self, rhs: R) -> Sugg<'static> {
144 make_assoc(AssocOp::As, &self, &Sugg::NonParen(rhs.to_string().into()))
147 /// Convenience method to create the `&<expr>` suggestion.
148 pub fn addr(self) -> Sugg<'static> {
152 /// Convenience method to create the `&mut <expr>` suggestion.
153 pub fn mut_addr(self) -> Sugg<'static> {
154 make_unop("&mut ", self)
157 /// Convenience method to create the `*<expr>` suggestion.
158 pub fn deref(self) -> Sugg<'static> {
162 /// Convenience method to create the `&*<expr>` suggestion. Currently this
163 /// is needed because `sugg.deref().addr()` produces an unnecessary set of
164 /// parentheses around the deref.
165 pub fn addr_deref(self) -> Sugg<'static> {
166 make_unop("&*", self)
169 /// Convenience method to create the `&mut *<expr>` suggestion. Currently
170 /// this is needed because `sugg.deref().mut_addr()` produces an unnecessary
171 /// set of parentheses around the deref.
172 pub fn mut_addr_deref(self) -> Sugg<'static> {
173 make_unop("&mut *", self)
176 /// Convenience method to create the `<lhs>..<rhs>` or `<lhs>...<rhs>`
178 pub fn range(self, end: &Self, limit: ast::RangeLimits) -> Sugg<'static> {
180 ast::RangeLimits::HalfOpen => make_assoc(AssocOp::DotDot, &self, end),
181 ast::RangeLimits::Closed => make_assoc(AssocOp::DotDotEq, &self, end),
185 /// Add parenthesis to any expression that might need them. Suitable to the
186 /// `self` argument of
187 /// a method call (eg. to build `bar.foo()` or `(1 + 2).foo()`).
188 pub fn maybe_par(self) -> Self {
190 Sugg::NonParen(..) => self,
191 // (x) and (x).y() both don't need additional parens
192 Sugg::MaybeParen(sugg) => if sugg.starts_with('(') && sugg.ends_with(')') {
193 Sugg::MaybeParen(sugg)
195 Sugg::NonParen(format!("({})", sugg).into())
197 Sugg::BinOp(_, sugg) => Sugg::NonParen(format!("({})", sugg).into()),
202 impl<'a, 'b> std::ops::Add<Sugg<'b>> for Sugg<'a> {
203 type Output = Sugg<'static>;
204 fn add(self, rhs: Sugg<'b>) -> Sugg<'static> {
205 make_binop(ast::BinOpKind::Add, &self, &rhs)
209 impl<'a, 'b> std::ops::Sub<Sugg<'b>> for Sugg<'a> {
210 type Output = Sugg<'static>;
211 fn sub(self, rhs: Sugg<'b>) -> Sugg<'static> {
212 make_binop(ast::BinOpKind::Sub, &self, &rhs)
216 impl<'a> std::ops::Not for Sugg<'a> {
217 type Output = Sugg<'static>;
218 fn not(self) -> Sugg<'static> {
223 /// Helper type to display either `foo` or `(foo)`.
224 struct ParenHelper<T> {
225 /// Whether parenthesis are needed.
227 /// The main thing to display.
231 impl<T> ParenHelper<T> {
232 /// Build a `ParenHelper`.
233 fn new(paren: bool, wrapped: T) -> Self {
241 impl<T: Display> Display for ParenHelper<T> {
242 fn fmt(&self, f: &mut std::fmt::Formatter) -> Result<(), std::fmt::Error> {
244 write!(f, "({})", self.wrapped)
251 /// Build the string for `<op><expr>` adding parenthesis when necessary.
253 /// For convenience, the operator is taken as a string because all unary
254 /// operators have the same
256 pub fn make_unop(op: &str, expr: Sugg) -> Sugg<'static> {
257 Sugg::MaybeParen(format!("{}{}", op, expr.maybe_par()).into())
260 /// Build the string for `<lhs> <op> <rhs>` adding parenthesis when necessary.
262 /// Precedence of shift operator relative to other arithmetic operation is
263 /// often confusing so
264 /// parenthesis will always be added for a mix of these.
265 pub fn make_assoc(op: AssocOp, lhs: &Sugg, rhs: &Sugg) -> Sugg<'static> {
266 /// Whether the operator is a shift operator `<<` or `>>`.
267 fn is_shift(op: &AssocOp) -> bool {
268 matches!(*op, AssocOp::ShiftLeft | AssocOp::ShiftRight)
271 /// Whether the operator is a arithmetic operator (`+`, `-`, `*`, `/`, `%`).
272 fn is_arith(op: &AssocOp) -> bool {
275 AssocOp::Add | AssocOp::Subtract | AssocOp::Multiply | AssocOp::Divide | AssocOp::Modulus
279 /// Whether the operator `op` needs parenthesis with the operator `other`
282 fn needs_paren(op: &AssocOp, other: &AssocOp, dir: Associativity) -> bool {
283 other.precedence() < op.precedence()
284 || (other.precedence() == op.precedence()
285 && ((op != other && associativity(op) != dir)
286 || (op == other && associativity(op) != Associativity::Both)))
287 || is_shift(op) && is_arith(other) || is_shift(other) && is_arith(op)
290 let lhs_paren = if let Sugg::BinOp(ref lop, _) = *lhs {
291 needs_paren(&op, lop, Associativity::Left)
296 let rhs_paren = if let Sugg::BinOp(ref rop, _) = *rhs {
297 needs_paren(&op, rop, Associativity::Right)
302 let lhs = ParenHelper::new(lhs_paren, lhs);
303 let rhs = ParenHelper::new(rhs_paren, rhs);
304 let sugg = match op {
312 AssocOp::GreaterEqual |
321 AssocOp::ShiftRight |
322 AssocOp::Subtract => format!("{} {} {}", lhs, op.to_ast_binop().expect("Those are AST ops").to_string(), rhs),
323 AssocOp::Assign => format!("{} = {}", lhs, rhs),
324 AssocOp::ObsoleteInPlace => format!("in ({}) {}", lhs, rhs),
325 AssocOp::AssignOp(op) => format!("{} {}= {}", lhs, token_to_string(&token::BinOp(op)), rhs),
326 AssocOp::As => format!("{} as {}", lhs, rhs),
327 AssocOp::DotDot => format!("{}..{}", lhs, rhs),
328 AssocOp::DotDotEq => format!("{}..={}", lhs, rhs),
329 AssocOp::Colon => format!("{}: {}", lhs, rhs),
332 Sugg::BinOp(op, sugg.into())
335 /// Convinience wrapper arround `make_assoc` and `AssocOp::from_ast_binop`.
336 pub fn make_binop(op: ast::BinOpKind, lhs: &Sugg, rhs: &Sugg) -> Sugg<'static> {
337 make_assoc(AssocOp::from_ast_binop(op), lhs, rhs)
340 #[derive(PartialEq, Eq, Clone, Copy)]
341 /// Operator associativity.
343 /// The operator is both left-associative and right-associative.
345 /// The operator is left-associative.
347 /// The operator is not associative.
349 /// The operator is right-associative.
353 /// Return the associativity/fixity of an operator. The difference with
354 /// `AssocOp::fixity` is that
355 /// an operator can be both left and right associative (such as `+`:
356 /// `a + b + c == (a + b) + c == a + (b + c)`.
358 /// Chained `as` and explicit `:` type coercion never need inner parenthesis so
359 /// they are considered
361 fn associativity(op: &AssocOp) -> Associativity {
362 use syntax::util::parser::AssocOp::*;
365 ObsoleteInPlace | Assign | AssignOp(_) => Associativity::Right,
366 Add | BitAnd | BitOr | BitXor | LAnd | LOr | Multiply | As | Colon => Associativity::Both,
377 Subtract => Associativity::Left,
378 DotDot | DotDotEq => Associativity::None,
382 /// Convert a `hir::BinOp` to the corresponding assigning binary operator.
383 fn hirbinop2assignop(op: hir::BinOp) -> AssocOp {
384 use rustc::hir::BinOp_::*;
385 use syntax::parse::token::BinOpToken::*;
387 AssocOp::AssignOp(match op.node {
398 BiAnd | BiEq | BiGe | BiGt | BiLe | BiLt | BiNe | BiOr => panic!("This operator does not exist"),
402 /// Convert an `ast::BinOp` to the corresponding assigning binary operator.
403 fn astbinop2assignop(op: ast::BinOp) -> AssocOp {
404 use syntax::ast::BinOpKind::*;
405 use syntax::parse::token::BinOpToken;
407 AssocOp::AssignOp(match op.node {
408 Add => BinOpToken::Plus,
409 BitAnd => BinOpToken::And,
410 BitOr => BinOpToken::Or,
411 BitXor => BinOpToken::Caret,
412 Div => BinOpToken::Slash,
413 Mul => BinOpToken::Star,
414 Rem => BinOpToken::Percent,
415 Shl => BinOpToken::Shl,
416 Shr => BinOpToken::Shr,
417 Sub => BinOpToken::Minus,
418 And | Eq | Ge | Gt | Le | Lt | Ne | Or => panic!("This operator does not exist"),
422 /// Return the indentation before `span` if there are nothing but `[ \t]`
423 /// before it on its line.
424 fn indentation<'a, T: LintContext<'a>>(cx: &T, span: Span) -> Option<String> {
425 let lo = cx.sess().codemap().lookup_char_pos(span.lo());
426 if let Some(line) = lo.file
427 .get_line(lo.line - 1 /* line numbers in `Loc` are 1-based */)
429 if let Some((pos, _)) = line.char_indices().find(|&(_, c)| c != ' ' && c != '\t') {
430 // we can mix char and byte positions here because we only consider `[ \t]`
431 if lo.col == CharPos(pos) {
432 Some(line[..pos].into())
444 /// Convenience extension trait for `DiagnosticBuilder`.
445 pub trait DiagnosticBuilderExt<'a, T: LintContext<'a>> {
446 /// Suggests to add an attribute to an item.
448 /// Correctly handles indentation of the attribute and item.
453 /// db.suggest_item_with_attr(cx, item, "#[derive(Default)]");
455 fn suggest_item_with_attr<D: Display + ?Sized>(&mut self, cx: &T, item: Span, msg: &str, attr: &D);
457 /// Suggest to add an item before another.
459 /// The item should not be indented (expect for inner indentation).
464 /// db.suggest_prepend_item(cx, item,
469 fn suggest_prepend_item(&mut self, cx: &T, item: Span, msg: &str, new_item: &str);
471 /// Suggest to completely remove an item.
473 /// This will remove an item and all following whitespace until the next non-whitespace
474 /// character. This should work correctly if item is on the same indentation level as the
480 /// db.suggest_remove_item(cx, item, "remove this")
482 fn suggest_remove_item(&mut self, cx: &T, item: Span, msg: &str);
485 impl<'a, 'b, 'c, T: LintContext<'c>> DiagnosticBuilderExt<'c, T> for rustc_errors::DiagnosticBuilder<'b> {
486 fn suggest_item_with_attr<D: Display + ?Sized>(&mut self, cx: &T, item: Span, msg: &str, attr: &D) {
487 if let Some(indent) = indentation(cx, item) {
488 let span = item.with_hi(item.lo());
490 self.span_suggestion(span, msg, format!("{}\n{}", attr, indent));
494 fn suggest_prepend_item(&mut self, cx: &T, item: Span, msg: &str, new_item: &str) {
495 if let Some(indent) = indentation(cx, item) {
496 let span = item.with_hi(item.lo());
498 let mut first = true;
499 let new_item = new_item
506 format!("{}{}\n", indent, l)
509 .collect::<String>();
511 self.span_suggestion(span, msg, format!("{}\n{}", new_item, indent));
515 fn suggest_remove_item(&mut self, cx: &T, item: Span, msg: &str) {
516 let mut remove_span = item;
517 let hi = cx.sess().codemap().next_point(remove_span).hi();
518 let fmpos = cx.sess().codemap().lookup_byte_offset(hi);
520 if let Some(ref src) = fmpos.fm.src {
521 let non_whitespace_offset = src[fmpos.pos.to_usize()..].find(|c| c != ' ' && c != '\t' && c != '\n');
523 if let Some(non_whitespace_offset) = non_whitespace_offset {
524 remove_span = remove_span.with_hi(remove_span.hi() + BytePos(non_whitespace_offset as u32))
528 self.span_suggestion(remove_span, msg, String::new());