rust-clippy/clippy_utils/src/higher.rs

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//! This module contains functions that retrieve specific elements.
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#![deny(clippy::missing_docs_in_private_items)]
use crate::consts::{constant_simple, Constant};
use crate::ty::is_type_diagnostic_item;
use crate::{is_expn_of, match_def_path, paths};
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use if_chain::if_chain;
use rustc_ast::ast;
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use rustc_hir as hir;
use rustc_hir::{Arm, Block, Expr, ExprKind, HirId, LoopSource, MatchSource, Node, Pat, QPath};
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use rustc_lint::LateContext;
use rustc_span::{sym, symbol, Span};
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/// The essential nodes of a desugared for loop as well as the entire span:
/// `for pat in arg { body }` becomes `(pat, arg, body)`. Return `(pat, arg, body, span)`.
pub struct ForLoop<'tcx> {
/// `for` loop item
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pub pat: &'tcx hir::Pat<'tcx>,
/// `IntoIterator` argument
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pub arg: &'tcx hir::Expr<'tcx>,
/// `for` loop body
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pub body: &'tcx hir::Expr<'tcx>,
/// Compare this against `hir::Destination.target`
pub loop_id: HirId,
/// entire `for` loop span
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pub span: Span,
}
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impl<'tcx> ForLoop<'tcx> {
/// Parses a desugared `for` loop
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pub fn hir(expr: &Expr<'tcx>) -> Option<Self> {
if_chain! {
if let hir::ExprKind::DropTemps(e) = expr.kind;
if let hir::ExprKind::Match(iterexpr, [arm], hir::MatchSource::ForLoopDesugar) = e.kind;
if let hir::ExprKind::Call(_, [arg]) = iterexpr.kind;
if let hir::ExprKind::Loop(block, ..) = arm.body.kind;
if let [stmt] = block.stmts;
if let hir::StmtKind::Expr(e) = stmt.kind;
if let hir::ExprKind::Match(_, [_, some_arm], _) = e.kind;
if let hir::PatKind::Struct(_, [field], _) = some_arm.pat.kind;
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then {
return Some(Self {
pat: field.pat,
arg,
body: some_arm.body,
loop_id: arm.body.hir_id,
span: expr.span.ctxt().outer_expn_data().call_site,
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});
}
}
None
}
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}
/// An `if` expression without `DropTemps`
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pub struct If<'hir> {
/// `if` condition
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pub cond: &'hir Expr<'hir>,
/// `if` then expression
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pub then: &'hir Expr<'hir>,
/// `else` expression
pub r#else: Option<&'hir Expr<'hir>>,
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}
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impl<'hir> If<'hir> {
#[inline]
/// Parses an `if` expression
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pub const fn hir(expr: &Expr<'hir>) -> Option<Self> {
if let ExprKind::If(
Expr {
kind: ExprKind::DropTemps(cond),
..
},
then,
r#else,
) = expr.kind
{
Some(Self { cond, then, r#else })
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} else {
None
}
}
}
/// An `if let` expression
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pub struct IfLet<'hir> {
/// `if let` pattern
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pub let_pat: &'hir Pat<'hir>,
/// `if let` scrutinee
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pub let_expr: &'hir Expr<'hir>,
/// `if let` then expression
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pub if_then: &'hir Expr<'hir>,
/// `if let` else expression
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pub if_else: Option<&'hir Expr<'hir>>,
}
impl<'hir> IfLet<'hir> {
/// Parses an `if let` expression
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pub fn hir(cx: &LateContext<'_>, expr: &Expr<'hir>) -> Option<Self> {
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if let ExprKind::If(
Expr {
kind:
ExprKind::Let(hir::Let {
pat: let_pat,
init: let_expr,
..
}),
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..
},
if_then,
if_else,
) = expr.kind
{
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let mut iter = cx.tcx.hir().parent_iter(expr.hir_id);
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if let Some((_, Node::Block(Block { stmts: [], .. }))) = iter.next() {
if let Some((
_,
Node::Expr(Expr {
kind: ExprKind::Loop(_, _, LoopSource::While, _),
..
}),
)) = iter.next()
{
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// while loop desugar
return None;
}
}
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return Some(Self {
let_pat,
let_expr,
if_then,
if_else,
});
}
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None
}
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}
/// An `if let` or `match` expression. Useful for lints that trigger on one or the other.
pub enum IfLetOrMatch<'hir> {
/// Any `match` expression
Match(&'hir Expr<'hir>, &'hir [Arm<'hir>], MatchSource),
/// scrutinee, pattern, then block, else block
IfLet(
&'hir Expr<'hir>,
&'hir Pat<'hir>,
&'hir Expr<'hir>,
Option<&'hir Expr<'hir>>,
),
}
impl<'hir> IfLetOrMatch<'hir> {
/// Parses an `if let` or `match` expression
pub fn parse(cx: &LateContext<'_>, expr: &Expr<'hir>) -> Option<Self> {
match expr.kind {
ExprKind::Match(expr, arms, source) => Some(Self::Match(expr, arms, source)),
_ => IfLet::hir(cx, expr).map(
|IfLet {
let_expr,
let_pat,
if_then,
if_else,
}| { Self::IfLet(let_expr, let_pat, if_then, if_else) },
),
}
}
}
/// An `if` or `if let` expression
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pub struct IfOrIfLet<'hir> {
/// `if` condition that is maybe a `let` expression
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pub cond: &'hir Expr<'hir>,
/// `if` then expression
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pub then: &'hir Expr<'hir>,
/// `else` expression
pub r#else: Option<&'hir Expr<'hir>>,
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}
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impl<'hir> IfOrIfLet<'hir> {
#[inline]
/// Parses an `if` or `if let` expression
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pub const fn hir(expr: &Expr<'hir>) -> Option<Self> {
if let ExprKind::If(cond, then, r#else) = expr.kind {
if let ExprKind::DropTemps(new_cond) = cond.kind {
return Some(Self {
cond: new_cond,
r#else,
then,
});
}
if let ExprKind::Let(..) = cond.kind {
return Some(Self { cond, then, r#else });
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}
}
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None
}
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}
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/// Represent a range akin to `ast::ExprKind::Range`.
#[derive(Debug, Copy, Clone)]
pub struct Range<'a> {
/// The lower bound of the range, or `None` for ranges such as `..X`.
pub start: Option<&'a hir::Expr<'a>>,
/// The upper bound of the range, or `None` for ranges such as `X..`.
pub end: Option<&'a hir::Expr<'a>>,
/// Whether the interval is open or closed.
pub limits: ast::RangeLimits,
}
impl<'a> Range<'a> {
/// Higher a `hir` range to something similar to `ast::ExprKind::Range`.
pub fn hir(expr: &'a hir::Expr<'_>) -> Option<Range<'a>> {
/// Finds the field named `name` in the field. Always return `Some` for
/// convenience.
fn get_field<'c>(name: &str, fields: &'c [hir::ExprField<'_>]) -> Option<&'c hir::Expr<'c>> {
let expr = &fields.iter().find(|field| field.ident.name.as_str() == name)?.expr;
Some(expr)
}
match expr.kind {
hir::ExprKind::Call(path, args)
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if matches!(
path.kind,
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hir::ExprKind::Path(hir::QPath::LangItem(hir::LangItem::RangeInclusiveNew, ..))
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) =>
{
Some(Range {
start: Some(&args[0]),
end: Some(&args[1]),
limits: ast::RangeLimits::Closed,
})
},
hir::ExprKind::Struct(path, fields, None) => match &path {
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hir::QPath::LangItem(hir::LangItem::RangeFull, ..) => Some(Range {
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start: None,
end: None,
limits: ast::RangeLimits::HalfOpen,
}),
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hir::QPath::LangItem(hir::LangItem::RangeFrom, ..) => Some(Range {
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start: Some(get_field("start", fields)?),
end: None,
limits: ast::RangeLimits::HalfOpen,
}),
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hir::QPath::LangItem(hir::LangItem::Range, ..) => Some(Range {
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start: Some(get_field("start", fields)?),
end: Some(get_field("end", fields)?),
limits: ast::RangeLimits::HalfOpen,
}),
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hir::QPath::LangItem(hir::LangItem::RangeToInclusive, ..) => Some(Range {
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start: None,
end: Some(get_field("end", fields)?),
limits: ast::RangeLimits::Closed,
}),
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hir::QPath::LangItem(hir::LangItem::RangeTo, ..) => Some(Range {
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start: None,
end: Some(get_field("end", fields)?),
limits: ast::RangeLimits::HalfOpen,
}),
_ => None,
},
_ => None,
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}
}
}
/// Represent the pre-expansion arguments of a `vec!` invocation.
pub enum VecArgs<'a> {
/// `vec![elem; len]`
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Repeat(&'a hir::Expr<'a>, &'a hir::Expr<'a>),
/// `vec![a, b, c]`
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Vec(&'a [hir::Expr<'a>]),
}
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impl<'a> VecArgs<'a> {
/// Returns the arguments of the `vec!` macro if this expression was expanded
/// from `vec!`.
pub fn hir(cx: &LateContext<'_>, expr: &'a hir::Expr<'_>) -> Option<VecArgs<'a>> {
if_chain! {
if let hir::ExprKind::Call(fun, args) = expr.kind;
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if let hir::ExprKind::Path(ref qpath) = fun.kind;
if is_expn_of(fun.span, "vec").is_some();
if let Some(fun_def_id) = cx.qpath_res(qpath, fun.hir_id).opt_def_id();
then {
return if match_def_path(cx, fun_def_id, &paths::VEC_FROM_ELEM) && args.len() == 2 {
// `vec![elem; size]` case
Some(VecArgs::Repeat(&args[0], &args[1]))
} else if match_def_path(cx, fun_def_id, &paths::SLICE_INTO_VEC) && args.len() == 1 {
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// `vec![a, b, c]` case
if let hir::ExprKind::Call(_, [arg]) = &args[0].kind
&& let hir::ExprKind::Array(args) = arg.kind {
Some(VecArgs::Vec(args))
} else {
None
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}
} else if match_def_path(cx, fun_def_id, &paths::VEC_NEW) && args.is_empty() {
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Some(VecArgs::Vec(&[]))
} else {
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None
};
}
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}
None
}
}
/// A desugared `while` loop
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pub struct While<'hir> {
/// `while` loop condition
pub condition: &'hir Expr<'hir>,
/// `while` loop body
pub body: &'hir Expr<'hir>,
/// Span of the loop header
pub span: Span,
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}
impl<'hir> While<'hir> {
#[inline]
/// Parses a desugared `while` loop
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pub const fn hir(expr: &Expr<'hir>) -> Option<Self> {
if let ExprKind::Loop(
Block {
expr:
Some(Expr {
kind:
ExprKind::If(
Expr {
kind: ExprKind::DropTemps(condition),
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..
},
body,
_,
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),
..
}),
..
},
_,
LoopSource::While,
span,
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) = expr.kind
{
return Some(Self { condition, body, span });
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}
None
}
}
/// A desugared `while let` loop
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pub struct WhileLet<'hir> {
/// `while let` loop item pattern
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pub let_pat: &'hir Pat<'hir>,
/// `while let` loop scrutinee
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pub let_expr: &'hir Expr<'hir>,
/// `while let` loop body
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pub if_then: &'hir Expr<'hir>,
}
impl<'hir> WhileLet<'hir> {
#[inline]
/// Parses a desugared `while let` loop
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pub const fn hir(expr: &Expr<'hir>) -> Option<Self> {
if let ExprKind::Loop(
Block {
expr:
Some(Expr {
kind:
ExprKind::If(
Expr {
kind:
ExprKind::Let(hir::Let {
pat: let_pat,
init: let_expr,
..
}),
..
},
if_then,
_,
),
..
}),
..
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},
_,
LoopSource::While,
_,
) = expr.kind
{
return Some(Self {
let_pat,
let_expr,
if_then,
});
}
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None
}
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}
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/// Converts a hir binary operator to the corresponding `ast` type.
#[must_use]
pub fn binop(op: hir::BinOpKind) -> ast::BinOpKind {
match op {
hir::BinOpKind::Eq => ast::BinOpKind::Eq,
hir::BinOpKind::Ge => ast::BinOpKind::Ge,
hir::BinOpKind::Gt => ast::BinOpKind::Gt,
hir::BinOpKind::Le => ast::BinOpKind::Le,
hir::BinOpKind::Lt => ast::BinOpKind::Lt,
hir::BinOpKind::Ne => ast::BinOpKind::Ne,
hir::BinOpKind::Or => ast::BinOpKind::Or,
hir::BinOpKind::Add => ast::BinOpKind::Add,
hir::BinOpKind::And => ast::BinOpKind::And,
hir::BinOpKind::BitAnd => ast::BinOpKind::BitAnd,
hir::BinOpKind::BitOr => ast::BinOpKind::BitOr,
hir::BinOpKind::BitXor => ast::BinOpKind::BitXor,
hir::BinOpKind::Div => ast::BinOpKind::Div,
hir::BinOpKind::Mul => ast::BinOpKind::Mul,
hir::BinOpKind::Rem => ast::BinOpKind::Rem,
hir::BinOpKind::Shl => ast::BinOpKind::Shl,
hir::BinOpKind::Shr => ast::BinOpKind::Shr,
hir::BinOpKind::Sub => ast::BinOpKind::Sub,
}
}
/// A parsed `Vec` initialization expression
#[derive(Clone, Copy)]
pub enum VecInitKind {
/// `Vec::new()`
New,
/// `Vec::default()` or `Default::default()`
Default,
/// `Vec::with_capacity(123)`
WithConstCapacity(u128),
/// `Vec::with_capacity(slice.len())`
WithExprCapacity(HirId),
}
/// Checks if given expression is an initialization of `Vec` and returns its kind.
pub fn get_vec_init_kind<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) -> Option<VecInitKind> {
if let ExprKind::Call(func, args) = expr.kind {
match func.kind {
ExprKind::Path(QPath::TypeRelative(ty, name))
if is_type_diagnostic_item(cx, cx.typeck_results().node_type(ty.hir_id), sym::Vec) =>
{
if name.ident.name == sym::new {
return Some(VecInitKind::New);
} else if name.ident.name == symbol::kw::Default {
return Some(VecInitKind::Default);
} else if name.ident.name.as_str() == "with_capacity" {
let arg = args.get(0)?;
return match constant_simple(cx, cx.typeck_results(), arg) {
Some(Constant::Int(num)) => Some(VecInitKind::WithConstCapacity(num)),
_ => Some(VecInitKind::WithExprCapacity(arg.hir_id)),
};
};
},
ExprKind::Path(QPath::Resolved(_, path))
if match_def_path(cx, path.res.opt_def_id()?, &paths::DEFAULT_TRAIT_METHOD)
&& is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(expr), sym::Vec) =>
{
return Some(VecInitKind::Default);
},
_ => (),
}
}
None
}