rust/clippy_utils/src/sugg.rs

1090 lines
42 KiB
Rust

//! Contains utility functions to generate suggestions.
#![deny(clippy::missing_docs_in_private_items)]
use crate::source::{snippet, snippet_opt, snippet_with_applicability, snippet_with_macro_callsite};
use crate::{get_parent_expr_for_hir, higher};
use rustc_ast::util::parser::AssocOp;
use rustc_ast::{ast, token};
use rustc_ast_pretty::pprust::token_kind_to_string;
use rustc_errors::Applicability;
use rustc_hir as hir;
use rustc_hir::{ExprKind, HirId, MutTy, TyKind};
use rustc_infer::infer::TyCtxtInferExt;
use rustc_lint::{EarlyContext, LateContext, LintContext};
use rustc_middle::hir::place::ProjectionKind;
use rustc_middle::mir::{FakeReadCause, Mutability};
use rustc_middle::ty;
use rustc_span::source_map::{BytePos, CharPos, Pos, Span, SyntaxContext};
use rustc_typeck::expr_use_visitor::{Delegate, ExprUseVisitor, PlaceBase, PlaceWithHirId};
use std::borrow::Cow;
use std::convert::TryInto;
use std::fmt::Display;
use std::iter;
use std::ops::{Add, Neg, Not, Sub};
/// A helper type to build suggestion correctly handling parentheses.
#[derive(Clone, PartialEq)]
pub enum Sugg<'a> {
/// An expression that never needs parentheses such as `1337` or `[0; 42]`.
NonParen(Cow<'a, str>),
/// An expression that does not fit in other variants.
MaybeParen(Cow<'a, str>),
/// A binary operator expression, including `as`-casts and explicit type
/// coercion.
BinOp(AssocOp, Cow<'a, str>, Cow<'a, str>),
}
/// Literal constant `0`, for convenience.
pub const ZERO: Sugg<'static> = Sugg::NonParen(Cow::Borrowed("0"));
/// Literal constant `1`, for convenience.
pub const ONE: Sugg<'static> = Sugg::NonParen(Cow::Borrowed("1"));
/// a constant represents an empty string, for convenience.
pub const EMPTY: Sugg<'static> = Sugg::NonParen(Cow::Borrowed(""));
impl Display for Sugg<'_> {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
match *self {
Sugg::NonParen(ref s) | Sugg::MaybeParen(ref s) => s.fmt(f),
Sugg::BinOp(op, ref lhs, ref rhs) => binop_to_string(op, lhs, rhs).fmt(f),
}
}
}
#[allow(clippy::wrong_self_convention)] // ok, because of the function `as_ty` method
impl<'a> Sugg<'a> {
/// Prepare a suggestion from an expression.
pub fn hir_opt(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option<Self> {
let get_snippet = |span| snippet(cx, span, "");
snippet_opt(cx, expr.span).map(|_| Self::hir_from_snippet(expr, get_snippet))
}
/// Convenience function around `hir_opt` for suggestions with a default
/// text.
pub fn hir(cx: &LateContext<'_>, expr: &hir::Expr<'_>, default: &'a str) -> Self {
Self::hir_opt(cx, expr).unwrap_or(Sugg::NonParen(Cow::Borrowed(default)))
}
/// Same as `hir`, but it adapts the applicability level by following rules:
///
/// - Applicability level `Unspecified` will never be changed.
/// - If the span is inside a macro, change the applicability level to `MaybeIncorrect`.
/// - If the default value is used and the applicability level is `MachineApplicable`, change it
/// to
/// `HasPlaceholders`
pub fn hir_with_applicability(
cx: &LateContext<'_>,
expr: &hir::Expr<'_>,
default: &'a str,
applicability: &mut Applicability,
) -> Self {
if *applicability != Applicability::Unspecified && expr.span.from_expansion() {
*applicability = Applicability::MaybeIncorrect;
}
Self::hir_opt(cx, expr).unwrap_or_else(|| {
if *applicability == Applicability::MachineApplicable {
*applicability = Applicability::HasPlaceholders;
}
Sugg::NonParen(Cow::Borrowed(default))
})
}
/// Same as `hir`, but will use the pre expansion span if the `expr` was in a macro.
pub fn hir_with_macro_callsite(cx: &LateContext<'_>, expr: &hir::Expr<'_>, default: &'a str) -> Self {
let get_snippet = |span| snippet_with_macro_callsite(cx, span, default);
Self::hir_from_snippet(expr, get_snippet)
}
/// Same as `hir`, but first walks the span up to the given context. This will result in the
/// macro call, rather then the expansion, if the span is from a child context. If the span is
/// not from a child context, it will be used directly instead.
///
/// e.g. Given the expression `&vec![]`, getting a snippet from the span for `vec![]` as a HIR
/// node would result in `box []`. If given the context of the address of expression, this
/// function will correctly get a snippet of `vec![]`.
pub fn hir_with_context(
cx: &LateContext<'_>,
expr: &hir::Expr<'_>,
ctxt: SyntaxContext,
default: &'a str,
applicability: &mut Applicability,
) -> Self {
if expr.span.ctxt() == ctxt {
Self::hir_from_snippet(expr, |span| snippet(cx, span, default))
} else {
let snip = snippet_with_applicability(cx, expr.span, default, applicability);
Sugg::NonParen(snip)
}
}
/// Generate a suggestion for an expression with the given snippet. This is used by the `hir_*`
/// function variants of `Sugg`, since these use different snippet functions.
fn hir_from_snippet(expr: &hir::Expr<'_>, get_snippet: impl Fn(Span) -> Cow<'a, str>) -> Self {
if let Some(range) = higher::Range::hir(expr) {
let op = match range.limits {
ast::RangeLimits::HalfOpen => AssocOp::DotDot,
ast::RangeLimits::Closed => AssocOp::DotDotEq,
};
let start = range.start.map_or("".into(), |expr| get_snippet(expr.span));
let end = range.end.map_or("".into(), |expr| get_snippet(expr.span));
return Sugg::BinOp(op, start, end);
}
match expr.kind {
hir::ExprKind::AddrOf(..)
| hir::ExprKind::Box(..)
| hir::ExprKind::If(..)
| hir::ExprKind::Let(..)
| hir::ExprKind::Closure(..)
| hir::ExprKind::Unary(..)
| hir::ExprKind::Match(..) => Sugg::MaybeParen(get_snippet(expr.span)),
hir::ExprKind::Continue(..)
| hir::ExprKind::Yield(..)
| hir::ExprKind::Array(..)
| hir::ExprKind::Block(..)
| hir::ExprKind::Break(..)
| hir::ExprKind::Call(..)
| hir::ExprKind::Field(..)
| hir::ExprKind::Index(..)
| hir::ExprKind::InlineAsm(..)
| hir::ExprKind::ConstBlock(..)
| hir::ExprKind::Lit(..)
| hir::ExprKind::Loop(..)
| hir::ExprKind::MethodCall(..)
| hir::ExprKind::Path(..)
| hir::ExprKind::Repeat(..)
| hir::ExprKind::Ret(..)
| hir::ExprKind::Struct(..)
| hir::ExprKind::Tup(..)
| hir::ExprKind::DropTemps(_)
| hir::ExprKind::Err => Sugg::NonParen(get_snippet(expr.span)),
hir::ExprKind::Assign(lhs, rhs, _) => {
Sugg::BinOp(AssocOp::Assign, get_snippet(lhs.span), get_snippet(rhs.span))
},
hir::ExprKind::AssignOp(op, lhs, rhs) => {
Sugg::BinOp(hirbinop2assignop(op), get_snippet(lhs.span), get_snippet(rhs.span))
},
hir::ExprKind::Binary(op, lhs, rhs) => Sugg::BinOp(
AssocOp::from_ast_binop(op.node.into()),
get_snippet(lhs.span),
get_snippet(rhs.span),
),
hir::ExprKind::Cast(lhs, ty) => Sugg::BinOp(AssocOp::As, get_snippet(lhs.span), get_snippet(ty.span)),
hir::ExprKind::Type(lhs, ty) => Sugg::BinOp(AssocOp::Colon, get_snippet(lhs.span), get_snippet(ty.span)),
}
}
/// Prepare a suggestion from an expression.
pub fn ast(cx: &EarlyContext<'_>, expr: &ast::Expr, default: &'a str) -> Self {
use rustc_ast::ast::RangeLimits;
let get_whole_snippet = || {
if expr.span.from_expansion() {
snippet_with_macro_callsite(cx, expr.span, default)
} else {
snippet(cx, expr.span, default)
}
};
match expr.kind {
ast::ExprKind::AddrOf(..)
| ast::ExprKind::Box(..)
| ast::ExprKind::Closure(..)
| ast::ExprKind::If(..)
| ast::ExprKind::Let(..)
| ast::ExprKind::Unary(..)
| ast::ExprKind::Match(..) => Sugg::MaybeParen(get_whole_snippet()),
ast::ExprKind::Async(..)
| ast::ExprKind::Block(..)
| ast::ExprKind::Break(..)
| ast::ExprKind::Call(..)
| ast::ExprKind::Continue(..)
| ast::ExprKind::Yield(..)
| ast::ExprKind::Field(..)
| ast::ExprKind::ForLoop(..)
| ast::ExprKind::Index(..)
| ast::ExprKind::InlineAsm(..)
| ast::ExprKind::ConstBlock(..)
| ast::ExprKind::Lit(..)
| ast::ExprKind::Loop(..)
| ast::ExprKind::MacCall(..)
| ast::ExprKind::MethodCall(..)
| ast::ExprKind::Paren(..)
| ast::ExprKind::Underscore
| ast::ExprKind::Path(..)
| ast::ExprKind::Repeat(..)
| ast::ExprKind::Ret(..)
| ast::ExprKind::Struct(..)
| ast::ExprKind::Try(..)
| ast::ExprKind::TryBlock(..)
| ast::ExprKind::Tup(..)
| ast::ExprKind::Array(..)
| ast::ExprKind::While(..)
| ast::ExprKind::Await(..)
| ast::ExprKind::Err => Sugg::NonParen(get_whole_snippet()),
ast::ExprKind::Range(ref lhs, ref rhs, RangeLimits::HalfOpen) => Sugg::BinOp(
AssocOp::DotDot,
lhs.as_ref().map_or("".into(), |lhs| snippet(cx, lhs.span, default)),
rhs.as_ref().map_or("".into(), |rhs| snippet(cx, rhs.span, default)),
),
ast::ExprKind::Range(ref lhs, ref rhs, RangeLimits::Closed) => Sugg::BinOp(
AssocOp::DotDotEq,
lhs.as_ref().map_or("".into(), |lhs| snippet(cx, lhs.span, default)),
rhs.as_ref().map_or("".into(), |rhs| snippet(cx, rhs.span, default)),
),
ast::ExprKind::Assign(ref lhs, ref rhs, _) => Sugg::BinOp(
AssocOp::Assign,
snippet(cx, lhs.span, default),
snippet(cx, rhs.span, default),
),
ast::ExprKind::AssignOp(op, ref lhs, ref rhs) => Sugg::BinOp(
astbinop2assignop(op),
snippet(cx, lhs.span, default),
snippet(cx, rhs.span, default),
),
ast::ExprKind::Binary(op, ref lhs, ref rhs) => Sugg::BinOp(
AssocOp::from_ast_binop(op.node),
snippet(cx, lhs.span, default),
snippet(cx, rhs.span, default),
),
ast::ExprKind::Cast(ref lhs, ref ty) => Sugg::BinOp(
AssocOp::As,
snippet(cx, lhs.span, default),
snippet(cx, ty.span, default),
),
ast::ExprKind::Type(ref lhs, ref ty) => Sugg::BinOp(
AssocOp::Colon,
snippet(cx, lhs.span, default),
snippet(cx, ty.span, default),
),
}
}
/// Convenience method to create the `<lhs> && <rhs>` suggestion.
pub fn and(self, rhs: &Self) -> Sugg<'static> {
make_binop(ast::BinOpKind::And, &self, rhs)
}
/// Convenience method to create the `<lhs> & <rhs>` suggestion.
pub fn bit_and(self, rhs: &Self) -> Sugg<'static> {
make_binop(ast::BinOpKind::BitAnd, &self, rhs)
}
/// Convenience method to create the `<lhs> as <rhs>` suggestion.
pub fn as_ty<R: Display>(self, rhs: R) -> Sugg<'static> {
make_assoc(AssocOp::As, &self, &Sugg::NonParen(rhs.to_string().into()))
}
/// Convenience method to create the `&<expr>` suggestion.
pub fn addr(self) -> Sugg<'static> {
make_unop("&", self)
}
/// Convenience method to create the `&mut <expr>` suggestion.
pub fn mut_addr(self) -> Sugg<'static> {
make_unop("&mut ", self)
}
/// Convenience method to create the `*<expr>` suggestion.
pub fn deref(self) -> Sugg<'static> {
make_unop("*", self)
}
/// Convenience method to create the `&*<expr>` suggestion. Currently this
/// is needed because `sugg.deref().addr()` produces an unnecessary set of
/// parentheses around the deref.
pub fn addr_deref(self) -> Sugg<'static> {
make_unop("&*", self)
}
/// Convenience method to create the `&mut *<expr>` suggestion. Currently
/// this is needed because `sugg.deref().mut_addr()` produces an unnecessary
/// set of parentheses around the deref.
pub fn mut_addr_deref(self) -> Sugg<'static> {
make_unop("&mut *", self)
}
/// Convenience method to transform suggestion into a return call
pub fn make_return(self) -> Sugg<'static> {
Sugg::NonParen(Cow::Owned(format!("return {}", self)))
}
/// Convenience method to transform suggestion into a block
/// where the suggestion is a trailing expression
pub fn blockify(self) -> Sugg<'static> {
Sugg::NonParen(Cow::Owned(format!("{{ {} }}", self)))
}
/// Convenience method to create the `<lhs>..<rhs>` or `<lhs>...<rhs>`
/// suggestion.
#[allow(dead_code)]
pub fn range(self, end: &Self, limit: ast::RangeLimits) -> Sugg<'static> {
match limit {
ast::RangeLimits::HalfOpen => make_assoc(AssocOp::DotDot, &self, end),
ast::RangeLimits::Closed => make_assoc(AssocOp::DotDotEq, &self, end),
}
}
/// Adds parentheses to any expression that might need them. Suitable to the
/// `self` argument of a method call
/// (e.g., to build `bar.foo()` or `(1 + 2).foo()`).
#[must_use]
pub fn maybe_par(self) -> Self {
match self {
Sugg::NonParen(..) => self,
// `(x)` and `(x).y()` both don't need additional parens.
Sugg::MaybeParen(sugg) => {
if has_enclosing_paren(&sugg) {
Sugg::MaybeParen(sugg)
} else {
Sugg::NonParen(format!("({})", sugg).into())
}
},
Sugg::BinOp(op, lhs, rhs) => {
let sugg = binop_to_string(op, &lhs, &rhs);
Sugg::NonParen(format!("({})", sugg).into())
},
}
}
}
/// Generates a string from the operator and both sides.
fn binop_to_string(op: AssocOp, lhs: &str, rhs: &str) -> String {
match op {
AssocOp::Add
| AssocOp::Subtract
| AssocOp::Multiply
| AssocOp::Divide
| AssocOp::Modulus
| AssocOp::LAnd
| AssocOp::LOr
| AssocOp::BitXor
| AssocOp::BitAnd
| AssocOp::BitOr
| AssocOp::ShiftLeft
| AssocOp::ShiftRight
| AssocOp::Equal
| AssocOp::Less
| AssocOp::LessEqual
| AssocOp::NotEqual
| AssocOp::Greater
| AssocOp::GreaterEqual => format!(
"{} {} {}",
lhs,
op.to_ast_binop().expect("Those are AST ops").to_string(),
rhs
),
AssocOp::Assign => format!("{} = {}", lhs, rhs),
AssocOp::AssignOp(op) => {
format!("{} {}= {}", lhs, token_kind_to_string(&token::BinOp(op)), rhs)
},
AssocOp::As => format!("{} as {}", lhs, rhs),
AssocOp::DotDot => format!("{}..{}", lhs, rhs),
AssocOp::DotDotEq => format!("{}..={}", lhs, rhs),
AssocOp::Colon => format!("{}: {}", lhs, rhs),
}
}
/// Return `true` if `sugg` is enclosed in parenthesis.
pub fn has_enclosing_paren(sugg: impl AsRef<str>) -> bool {
let mut chars = sugg.as_ref().chars();
if chars.next() == Some('(') {
let mut depth = 1;
for c in &mut chars {
if c == '(' {
depth += 1;
} else if c == ')' {
depth -= 1;
}
if depth == 0 {
break;
}
}
chars.next().is_none()
} else {
false
}
}
/// Copied from the rust standard library, and then edited
macro_rules! forward_binop_impls_to_ref {
(impl $imp:ident, $method:ident for $t:ty, type Output = $o:ty) => {
impl $imp<$t> for &$t {
type Output = $o;
fn $method(self, other: $t) -> $o {
$imp::$method(self, &other)
}
}
impl $imp<&$t> for $t {
type Output = $o;
fn $method(self, other: &$t) -> $o {
$imp::$method(&self, other)
}
}
impl $imp for $t {
type Output = $o;
fn $method(self, other: $t) -> $o {
$imp::$method(&self, &other)
}
}
};
}
impl Add for &Sugg<'_> {
type Output = Sugg<'static>;
fn add(self, rhs: &Sugg<'_>) -> Sugg<'static> {
make_binop(ast::BinOpKind::Add, self, rhs)
}
}
impl Sub for &Sugg<'_> {
type Output = Sugg<'static>;
fn sub(self, rhs: &Sugg<'_>) -> Sugg<'static> {
make_binop(ast::BinOpKind::Sub, self, rhs)
}
}
forward_binop_impls_to_ref!(impl Add, add for Sugg<'_>, type Output = Sugg<'static>);
forward_binop_impls_to_ref!(impl Sub, sub for Sugg<'_>, type Output = Sugg<'static>);
impl Neg for Sugg<'_> {
type Output = Sugg<'static>;
fn neg(self) -> Sugg<'static> {
make_unop("-", self)
}
}
impl<'a> Not for Sugg<'a> {
type Output = Sugg<'a>;
fn not(self) -> Sugg<'a> {
use AssocOp::{Equal, Greater, GreaterEqual, Less, LessEqual, NotEqual};
if let Sugg::BinOp(op, lhs, rhs) = self {
let to_op = match op {
Equal => NotEqual,
NotEqual => Equal,
Less => GreaterEqual,
GreaterEqual => Less,
Greater => LessEqual,
LessEqual => Greater,
_ => return make_unop("!", Sugg::BinOp(op, lhs, rhs)),
};
Sugg::BinOp(to_op, lhs, rhs)
} else {
make_unop("!", self)
}
}
}
/// Helper type to display either `foo` or `(foo)`.
struct ParenHelper<T> {
/// `true` if parentheses are needed.
paren: bool,
/// The main thing to display.
wrapped: T,
}
impl<T> ParenHelper<T> {
/// Builds a `ParenHelper`.
fn new(paren: bool, wrapped: T) -> Self {
Self { paren, wrapped }
}
}
impl<T: Display> Display for ParenHelper<T> {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
if self.paren {
write!(f, "({})", self.wrapped)
} else {
self.wrapped.fmt(f)
}
}
}
/// Builds the string for `<op><expr>` adding parenthesis when necessary.
///
/// For convenience, the operator is taken as a string because all unary
/// operators have the same
/// precedence.
pub fn make_unop(op: &str, expr: Sugg<'_>) -> Sugg<'static> {
Sugg::MaybeParen(format!("{}{}", op, expr.maybe_par()).into())
}
/// Builds the string for `<lhs> <op> <rhs>` adding parenthesis when necessary.
///
/// Precedence of shift operator relative to other arithmetic operation is
/// often confusing so
/// parenthesis will always be added for a mix of these.
pub fn make_assoc(op: AssocOp, lhs: &Sugg<'_>, rhs: &Sugg<'_>) -> Sugg<'static> {
/// Returns `true` if the operator is a shift operator `<<` or `>>`.
fn is_shift(op: AssocOp) -> bool {
matches!(op, AssocOp::ShiftLeft | AssocOp::ShiftRight)
}
/// Returns `true` if the operator is an arithmetic operator
/// (i.e., `+`, `-`, `*`, `/`, `%`).
fn is_arith(op: AssocOp) -> bool {
matches!(
op,
AssocOp::Add | AssocOp::Subtract | AssocOp::Multiply | AssocOp::Divide | AssocOp::Modulus
)
}
/// Returns `true` if the operator `op` needs parenthesis with the operator
/// `other` in the direction `dir`.
fn needs_paren(op: AssocOp, other: AssocOp, dir: Associativity) -> bool {
other.precedence() < op.precedence()
|| (other.precedence() == op.precedence()
&& ((op != other && associativity(op) != dir)
|| (op == other && associativity(op) != Associativity::Both)))
|| is_shift(op) && is_arith(other)
|| is_shift(other) && is_arith(op)
}
let lhs_paren = if let Sugg::BinOp(lop, _, _) = *lhs {
needs_paren(op, lop, Associativity::Left)
} else {
false
};
let rhs_paren = if let Sugg::BinOp(rop, _, _) = *rhs {
needs_paren(op, rop, Associativity::Right)
} else {
false
};
let lhs = ParenHelper::new(lhs_paren, lhs).to_string();
let rhs = ParenHelper::new(rhs_paren, rhs).to_string();
Sugg::BinOp(op, lhs.into(), rhs.into())
}
/// Convenience wrapper around `make_assoc` and `AssocOp::from_ast_binop`.
pub fn make_binop(op: ast::BinOpKind, lhs: &Sugg<'_>, rhs: &Sugg<'_>) -> Sugg<'static> {
make_assoc(AssocOp::from_ast_binop(op), lhs, rhs)
}
#[derive(PartialEq, Eq, Clone, Copy)]
/// Operator associativity.
enum Associativity {
/// The operator is both left-associative and right-associative.
Both,
/// The operator is left-associative.
Left,
/// The operator is not associative.
None,
/// The operator is right-associative.
Right,
}
/// Returns the associativity/fixity of an operator. The difference with
/// `AssocOp::fixity` is that an operator can be both left and right associative
/// (such as `+`: `a + b + c == (a + b) + c == a + (b + c)`.
///
/// Chained `as` and explicit `:` type coercion never need inner parenthesis so
/// they are considered
/// associative.
#[must_use]
fn associativity(op: AssocOp) -> Associativity {
use rustc_ast::util::parser::AssocOp::{
Add, As, Assign, AssignOp, BitAnd, BitOr, BitXor, Colon, Divide, DotDot, DotDotEq, Equal, Greater,
GreaterEqual, LAnd, LOr, Less, LessEqual, Modulus, Multiply, NotEqual, ShiftLeft, ShiftRight, Subtract,
};
match op {
Assign | AssignOp(_) => Associativity::Right,
Add | BitAnd | BitOr | BitXor | LAnd | LOr | Multiply | As | Colon => Associativity::Both,
Divide | Equal | Greater | GreaterEqual | Less | LessEqual | Modulus | NotEqual | ShiftLeft | ShiftRight
| Subtract => Associativity::Left,
DotDot | DotDotEq => Associativity::None,
}
}
/// Converts a `hir::BinOp` to the corresponding assigning binary operator.
fn hirbinop2assignop(op: hir::BinOp) -> AssocOp {
use rustc_ast::token::BinOpToken::{And, Caret, Minus, Or, Percent, Plus, Shl, Shr, Slash, Star};
AssocOp::AssignOp(match op.node {
hir::BinOpKind::Add => Plus,
hir::BinOpKind::BitAnd => And,
hir::BinOpKind::BitOr => Or,
hir::BinOpKind::BitXor => Caret,
hir::BinOpKind::Div => Slash,
hir::BinOpKind::Mul => Star,
hir::BinOpKind::Rem => Percent,
hir::BinOpKind::Shl => Shl,
hir::BinOpKind::Shr => Shr,
hir::BinOpKind::Sub => Minus,
hir::BinOpKind::And
| hir::BinOpKind::Eq
| hir::BinOpKind::Ge
| hir::BinOpKind::Gt
| hir::BinOpKind::Le
| hir::BinOpKind::Lt
| hir::BinOpKind::Ne
| hir::BinOpKind::Or => panic!("This operator does not exist"),
})
}
/// Converts an `ast::BinOp` to the corresponding assigning binary operator.
fn astbinop2assignop(op: ast::BinOp) -> AssocOp {
use rustc_ast::ast::BinOpKind::{
Add, And, BitAnd, BitOr, BitXor, Div, Eq, Ge, Gt, Le, Lt, Mul, Ne, Or, Rem, Shl, Shr, Sub,
};
use rustc_ast::token::BinOpToken;
AssocOp::AssignOp(match op.node {
Add => BinOpToken::Plus,
BitAnd => BinOpToken::And,
BitOr => BinOpToken::Or,
BitXor => BinOpToken::Caret,
Div => BinOpToken::Slash,
Mul => BinOpToken::Star,
Rem => BinOpToken::Percent,
Shl => BinOpToken::Shl,
Shr => BinOpToken::Shr,
Sub => BinOpToken::Minus,
And | Eq | Ge | Gt | Le | Lt | Ne | Or => panic!("This operator does not exist"),
})
}
/// Returns the indentation before `span` if there are nothing but `[ \t]`
/// before it on its line.
fn indentation<T: LintContext>(cx: &T, span: Span) -> Option<String> {
let lo = cx.sess().source_map().lookup_char_pos(span.lo());
lo.file
.get_line(lo.line - 1 /* line numbers in `Loc` are 1-based */)
.and_then(|line| {
if let Some((pos, _)) = line.char_indices().find(|&(_, c)| c != ' ' && c != '\t') {
// We can mix char and byte positions here because we only consider `[ \t]`.
if lo.col == CharPos(pos) {
Some(line[..pos].into())
} else {
None
}
} else {
None
}
})
}
/// Convenience extension trait for `Diagnostic`.
pub trait DiagnosticExt<T: LintContext> {
/// Suggests to add an attribute to an item.
///
/// Correctly handles indentation of the attribute and item.
///
/// # Example
///
/// ```rust,ignore
/// diag.suggest_item_with_attr(cx, item, "#[derive(Default)]");
/// ```
fn suggest_item_with_attr<D: Display + ?Sized>(
&mut self,
cx: &T,
item: Span,
msg: &str,
attr: &D,
applicability: Applicability,
);
/// Suggest to add an item before another.
///
/// The item should not be indented (except for inner indentation).
///
/// # Example
///
/// ```rust,ignore
/// diag.suggest_prepend_item(cx, item,
/// "fn foo() {
/// bar();
/// }");
/// ```
fn suggest_prepend_item(&mut self, cx: &T, item: Span, msg: &str, new_item: &str, applicability: Applicability);
/// Suggest to completely remove an item.
///
/// This will remove an item and all following whitespace until the next non-whitespace
/// character. This should work correctly if item is on the same indentation level as the
/// following item.
///
/// # Example
///
/// ```rust,ignore
/// diag.suggest_remove_item(cx, item, "remove this")
/// ```
fn suggest_remove_item(&mut self, cx: &T, item: Span, msg: &str, applicability: Applicability);
}
impl<T: LintContext> DiagnosticExt<T> for rustc_errors::Diagnostic {
fn suggest_item_with_attr<D: Display + ?Sized>(
&mut self,
cx: &T,
item: Span,
msg: &str,
attr: &D,
applicability: Applicability,
) {
if let Some(indent) = indentation(cx, item) {
let span = item.with_hi(item.lo());
self.span_suggestion(span, msg, format!("{}\n{}", attr, indent), applicability);
}
}
fn suggest_prepend_item(&mut self, cx: &T, item: Span, msg: &str, new_item: &str, applicability: Applicability) {
if let Some(indent) = indentation(cx, item) {
let span = item.with_hi(item.lo());
let mut first = true;
let new_item = new_item
.lines()
.map(|l| {
if first {
first = false;
format!("{}\n", l)
} else {
format!("{}{}\n", indent, l)
}
})
.collect::<String>();
self.span_suggestion(span, msg, format!("{}\n{}", new_item, indent), applicability);
}
}
fn suggest_remove_item(&mut self, cx: &T, item: Span, msg: &str, applicability: Applicability) {
let mut remove_span = item;
let hi = cx.sess().source_map().next_point(remove_span).hi();
let fmpos = cx.sess().source_map().lookup_byte_offset(hi);
if let Some(ref src) = fmpos.sf.src {
let non_whitespace_offset = src[fmpos.pos.to_usize()..].find(|c| c != ' ' && c != '\t' && c != '\n');
if let Some(non_whitespace_offset) = non_whitespace_offset {
remove_span = remove_span
.with_hi(remove_span.hi() + BytePos(non_whitespace_offset.try_into().expect("offset too large")));
}
}
self.span_suggestion(remove_span, msg, String::new(), applicability);
}
}
/// Suggestion results for handling closure
/// args dereferencing and borrowing
pub struct DerefClosure {
/// confidence on the built suggestion
pub applicability: Applicability,
/// gradually built suggestion
pub suggestion: String,
}
/// Build suggestion gradually by handling closure arg specific usages,
/// such as explicit deref and borrowing cases.
/// Returns `None` if no such use cases have been triggered in closure body
///
/// note: this only works on single line immutable closures with exactly one input parameter.
pub fn deref_closure_args<'tcx>(cx: &LateContext<'_>, closure: &'tcx hir::Expr<'_>) -> Option<DerefClosure> {
if let hir::ExprKind::Closure(_, fn_decl, body_id, ..) = closure.kind {
let closure_body = cx.tcx.hir().body(body_id);
// is closure arg a type annotated double reference (i.e.: `|x: &&i32| ...`)
// a type annotation is present if param `kind` is different from `TyKind::Infer`
let closure_arg_is_type_annotated_double_ref = if let TyKind::Rptr(_, MutTy { ty, .. }) = fn_decl.inputs[0].kind
{
matches!(ty.kind, TyKind::Rptr(_, MutTy { .. }))
} else {
false
};
let mut visitor = DerefDelegate {
cx,
closure_span: closure.span,
closure_arg_is_type_annotated_double_ref,
next_pos: closure.span.lo(),
suggestion_start: String::new(),
applicability: Applicability::MachineApplicable,
};
let fn_def_id = cx.tcx.hir().local_def_id(closure.hir_id);
cx.tcx.infer_ctxt().enter(|infcx| {
ExprUseVisitor::new(&mut visitor, &infcx, fn_def_id, cx.param_env, cx.typeck_results())
.consume_body(closure_body);
});
if !visitor.suggestion_start.is_empty() {
return Some(DerefClosure {
applicability: visitor.applicability,
suggestion: visitor.finish(),
});
}
}
None
}
/// Visitor struct used for tracking down
/// dereferencing and borrowing of closure's args
struct DerefDelegate<'a, 'tcx> {
/// The late context of the lint
cx: &'a LateContext<'tcx>,
/// The span of the input closure to adapt
closure_span: Span,
/// Indicates if the arg of the closure is a type annotated double reference
closure_arg_is_type_annotated_double_ref: bool,
/// last position of the span to gradually build the suggestion
next_pos: BytePos,
/// starting part of the gradually built suggestion
suggestion_start: String,
/// confidence on the built suggestion
applicability: Applicability,
}
impl<'tcx> DerefDelegate<'_, 'tcx> {
/// build final suggestion:
/// - create the ending part of suggestion
/// - concatenate starting and ending parts
/// - potentially remove needless borrowing
pub fn finish(&mut self) -> String {
let end_span = Span::new(self.next_pos, self.closure_span.hi(), self.closure_span.ctxt(), None);
let end_snip = snippet_with_applicability(self.cx, end_span, "..", &mut self.applicability);
let sugg = format!("{}{}", self.suggestion_start, end_snip);
if self.closure_arg_is_type_annotated_double_ref {
sugg.replacen('&', "", 1)
} else {
sugg
}
}
/// indicates whether the function from `parent_expr` takes its args by double reference
fn func_takes_arg_by_double_ref(&self, parent_expr: &'tcx hir::Expr<'_>, cmt_hir_id: HirId) -> bool {
let (call_args, inputs) = match parent_expr.kind {
ExprKind::MethodCall(_, call_args, _) => {
if let Some(method_did) = self.cx.typeck_results().type_dependent_def_id(parent_expr.hir_id) {
(call_args, self.cx.tcx.fn_sig(method_did).skip_binder().inputs())
} else {
return false;
}
},
ExprKind::Call(func, call_args) => {
let typ = self.cx.typeck_results().expr_ty(func);
(call_args, typ.fn_sig(self.cx.tcx).skip_binder().inputs())
},
_ => return false,
};
iter::zip(call_args, inputs)
.any(|(arg, ty)| arg.hir_id == cmt_hir_id && matches!(ty.kind(), ty::Ref(_, inner, _) if inner.is_ref()))
}
}
impl<'tcx> Delegate<'tcx> for DerefDelegate<'_, 'tcx> {
fn consume(&mut self, _: &PlaceWithHirId<'tcx>, _: HirId) {}
#[allow(clippy::too_many_lines)]
fn borrow(&mut self, cmt: &PlaceWithHirId<'tcx>, _: HirId, _: ty::BorrowKind) {
if let PlaceBase::Local(id) = cmt.place.base {
let map = self.cx.tcx.hir();
let span = map.span(cmt.hir_id);
let start_span = Span::new(self.next_pos, span.lo(), span.ctxt(), None);
let mut start_snip = snippet_with_applicability(self.cx, start_span, "..", &mut self.applicability);
// identifier referring to the variable currently triggered (i.e.: `fp`)
let ident_str = map.name(id).to_string();
// full identifier that includes projection (i.e.: `fp.field`)
let ident_str_with_proj = snippet(self.cx, span, "..").to_string();
if cmt.place.projections.is_empty() {
// handle item without any projection, that needs an explicit borrowing
// i.e.: suggest `&x` instead of `x`
self.suggestion_start.push_str(&format!("{}&{}", start_snip, ident_str));
} else {
// cases where a parent `Call` or `MethodCall` is using the item
// i.e.: suggest `.contains(&x)` for `.find(|x| [1, 2, 3].contains(x)).is_none()`
//
// Note about method calls:
// - compiler automatically dereference references if the target type is a reference (works also for
// function call)
// - `self` arguments in the case of `x.is_something()` are also automatically (de)referenced, and
// no projection should be suggested
if let Some(parent_expr) = get_parent_expr_for_hir(self.cx, cmt.hir_id) {
match &parent_expr.kind {
// given expression is the self argument and will be handled completely by the compiler
// i.e.: `|x| x.is_something()`
ExprKind::MethodCall(_, [self_expr, ..], _) if self_expr.hir_id == cmt.hir_id => {
self.suggestion_start
.push_str(&format!("{}{}", start_snip, ident_str_with_proj));
self.next_pos = span.hi();
return;
},
// item is used in a call
// i.e.: `Call`: `|x| please(x)` or `MethodCall`: `|x| [1, 2, 3].contains(x)`
ExprKind::Call(_, [call_args @ ..]) | ExprKind::MethodCall(_, [_, call_args @ ..], _) => {
let expr = self.cx.tcx.hir().expect_expr(cmt.hir_id);
let arg_ty_kind = self.cx.typeck_results().expr_ty(expr).kind();
if matches!(arg_ty_kind, ty::Ref(_, _, Mutability::Not)) {
// suggest ampersand if call function is taking args by double reference
let takes_arg_by_double_ref =
self.func_takes_arg_by_double_ref(parent_expr, cmt.hir_id);
// compiler will automatically dereference field or index projection, so no need
// to suggest ampersand, but full identifier that includes projection is required
let has_field_or_index_projection =
cmt.place.projections.iter().any(|proj| {
matches!(proj.kind, ProjectionKind::Field(..) | ProjectionKind::Index)
});
// no need to bind again if the function doesn't take arg by double ref
// and if the item is already a double ref
let ident_sugg = if !call_args.is_empty()
&& !takes_arg_by_double_ref
&& (self.closure_arg_is_type_annotated_double_ref || has_field_or_index_projection)
{
let ident = if has_field_or_index_projection {
ident_str_with_proj
} else {
ident_str
};
format!("{}{}", start_snip, ident)
} else {
format!("{}&{}", start_snip, ident_str)
};
self.suggestion_start.push_str(&ident_sugg);
self.next_pos = span.hi();
return;
}
self.applicability = Applicability::Unspecified;
},
_ => (),
}
}
let mut replacement_str = ident_str;
let mut projections_handled = false;
cmt.place.projections.iter().enumerate().for_each(|(i, proj)| {
match proj.kind {
// Field projection like `|v| v.foo`
// no adjustment needed here, as field projections are handled by the compiler
ProjectionKind::Field(..) => match cmt.place.ty_before_projection(i).kind() {
ty::Adt(..) | ty::Tuple(_) => {
replacement_str = ident_str_with_proj.clone();
projections_handled = true;
},
_ => (),
},
// Index projection like `|x| foo[x]`
// the index is dropped so we can't get it to build the suggestion,
// so the span is set-up again to get more code, using `span.hi()` (i.e.: `foo[x]`)
// instead of `span.lo()` (i.e.: `foo`)
ProjectionKind::Index => {
let start_span = Span::new(self.next_pos, span.hi(), span.ctxt(), None);
start_snip = snippet_with_applicability(self.cx, start_span, "..", &mut self.applicability);
replacement_str.clear();
projections_handled = true;
},
// note: unable to trigger `Subslice` kind in tests
ProjectionKind::Subslice => (),
ProjectionKind::Deref => {
// Explicit derefs are typically handled later on, but
// some items do not need explicit deref, such as array accesses,
// so we mark them as already processed
// i.e.: don't suggest `*sub[1..4].len()` for `|sub| sub[1..4].len() == 3`
if let ty::Ref(_, inner, _) = cmt.place.ty_before_projection(i).kind() {
if matches!(inner.kind(), ty::Ref(_, innermost, _) if innermost.is_array()) {
projections_handled = true;
}
}
},
}
});
// handle `ProjectionKind::Deref` by removing one explicit deref
// if no special case was detected (i.e.: suggest `*x` instead of `**x`)
if !projections_handled {
let last_deref = cmt
.place
.projections
.iter()
.rposition(|proj| proj.kind == ProjectionKind::Deref);
if let Some(pos) = last_deref {
let mut projections = cmt.place.projections.clone();
projections.truncate(pos);
for item in projections {
if item.kind == ProjectionKind::Deref {
replacement_str = format!("*{}", replacement_str);
}
}
}
}
self.suggestion_start
.push_str(&format!("{}{}", start_snip, replacement_str));
}
self.next_pos = span.hi();
}
}
fn mutate(&mut self, _: &PlaceWithHirId<'tcx>, _: HirId) {}
fn fake_read(&mut self, _: rustc_typeck::expr_use_visitor::Place<'tcx>, _: FakeReadCause, _: HirId) {}
}
#[cfg(test)]
mod test {
use super::Sugg;
use rustc_ast::util::parser::AssocOp;
use std::borrow::Cow;
const SUGGESTION: Sugg<'static> = Sugg::NonParen(Cow::Borrowed("function_call()"));
#[test]
fn make_return_transform_sugg_into_a_return_call() {
assert_eq!("return function_call()", SUGGESTION.make_return().to_string());
}
#[test]
fn blockify_transforms_sugg_into_a_block() {
assert_eq!("{ function_call() }", SUGGESTION.blockify().to_string());
}
#[test]
fn binop_maybe_par() {
let sugg = Sugg::BinOp(AssocOp::Add, "1".into(), "1".into());
assert_eq!("(1 + 1)", sugg.maybe_par().to_string());
let sugg = Sugg::BinOp(AssocOp::Add, "(1 + 1)".into(), "(1 + 1)".into());
assert_eq!("((1 + 1) + (1 + 1))", sugg.maybe_par().to_string());
}
#[test]
fn not_op() {
use AssocOp::{Add, Equal, Greater, GreaterEqual, LAnd, LOr, Less, LessEqual, NotEqual};
fn test_not(op: AssocOp, correct: &str) {
let sugg = Sugg::BinOp(op, "x".into(), "y".into());
assert_eq!((!sugg).to_string(), correct);
}
// Invert the comparison operator.
test_not(Equal, "x != y");
test_not(NotEqual, "x == y");
test_not(Less, "x >= y");
test_not(LessEqual, "x > y");
test_not(Greater, "x <= y");
test_not(GreaterEqual, "x < y");
// Other operators are inverted like !(..).
test_not(Add, "!(x + y)");
test_not(LAnd, "!(x && y)");
test_not(LOr, "!(x || y)");
}
}