291 lines
10 KiB
Rust
291 lines
10 KiB
Rust
//! This module contains functions for retrieve the original AST from lowered
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//! `hir`.
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#![deny(clippy::missing_docs_in_private_items)]
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use crate::utils::{is_expn_of, match_def_path, match_qpath, paths};
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use if_chain::if_chain;
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use rustc_ast::ast;
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use rustc_hir as hir;
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use rustc_lint::LateContext;
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use rustc_middle::ty;
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/// Converts a hir binary operator to the corresponding `ast` type.
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#[must_use]
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pub fn binop(op: hir::BinOpKind) -> ast::BinOpKind {
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match op {
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hir::BinOpKind::Eq => ast::BinOpKind::Eq,
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hir::BinOpKind::Ge => ast::BinOpKind::Ge,
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hir::BinOpKind::Gt => ast::BinOpKind::Gt,
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hir::BinOpKind::Le => ast::BinOpKind::Le,
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hir::BinOpKind::Lt => ast::BinOpKind::Lt,
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hir::BinOpKind::Ne => ast::BinOpKind::Ne,
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hir::BinOpKind::Or => ast::BinOpKind::Or,
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hir::BinOpKind::Add => ast::BinOpKind::Add,
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hir::BinOpKind::And => ast::BinOpKind::And,
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hir::BinOpKind::BitAnd => ast::BinOpKind::BitAnd,
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hir::BinOpKind::BitOr => ast::BinOpKind::BitOr,
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hir::BinOpKind::BitXor => ast::BinOpKind::BitXor,
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hir::BinOpKind::Div => ast::BinOpKind::Div,
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hir::BinOpKind::Mul => ast::BinOpKind::Mul,
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hir::BinOpKind::Rem => ast::BinOpKind::Rem,
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hir::BinOpKind::Shl => ast::BinOpKind::Shl,
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hir::BinOpKind::Shr => ast::BinOpKind::Shr,
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hir::BinOpKind::Sub => ast::BinOpKind::Sub,
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}
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}
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/// Represent a range akin to `ast::ExprKind::Range`.
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#[derive(Debug, Copy, Clone)]
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pub struct Range<'a> {
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/// The lower bound of the range, or `None` for ranges such as `..X`.
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pub start: Option<&'a hir::Expr<'a>>,
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/// The upper bound of the range, or `None` for ranges such as `X..`.
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pub end: Option<&'a hir::Expr<'a>>,
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/// Whether the interval is open or closed.
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pub limits: ast::RangeLimits,
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}
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/// Higher a `hir` range to something similar to `ast::ExprKind::Range`.
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pub fn range<'a, 'b, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'b hir::Expr<'_>) -> Option<Range<'b>> {
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/// Finds the field named `name` in the field. Always return `Some` for
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/// convenience.
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fn get_field<'c>(name: &str, fields: &'c [hir::Field<'_>]) -> Option<&'c hir::Expr<'c>> {
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let expr = &fields.iter().find(|field| field.ident.name.as_str() == name)?.expr;
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Some(expr)
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}
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let def_path = match cx.tables.expr_ty(expr).kind {
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ty::Adt(def, _) => cx.tcx.def_path(def.did),
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_ => return None,
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};
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// sanity checks for std::ops::RangeXXXX
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if def_path.data.len() != 3 {
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return None;
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}
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if def_path.data.get(0)?.data.as_symbol() != sym!(ops) {
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return None;
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}
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if def_path.data.get(1)?.data.as_symbol() != sym!(range) {
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return None;
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}
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let type_name = def_path.data.get(2)?.data.as_symbol();
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let range_types = [
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"RangeFrom",
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"RangeFull",
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"RangeInclusive",
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"Range",
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"RangeTo",
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"RangeToInclusive",
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];
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if !range_types.contains(&&*type_name.as_str()) {
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return None;
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}
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// The range syntax is expanded to literal paths starting with `core` or `std`
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// depending on
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// `#[no_std]`. Testing both instead of resolving the paths.
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match expr.kind {
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hir::ExprKind::Path(ref path) => {
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if match_qpath(path, &paths::RANGE_FULL_STD) || match_qpath(path, &paths::RANGE_FULL) {
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Some(Range {
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start: None,
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end: None,
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limits: ast::RangeLimits::HalfOpen,
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})
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} else {
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None
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}
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},
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hir::ExprKind::Call(ref path, ref args) => {
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if let hir::ExprKind::Path(ref path) = path.kind {
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if match_qpath(path, &paths::RANGE_INCLUSIVE_STD_NEW) || match_qpath(path, &paths::RANGE_INCLUSIVE_NEW)
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{
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Some(Range {
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start: Some(&args[0]),
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end: Some(&args[1]),
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limits: ast::RangeLimits::Closed,
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})
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} else {
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None
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}
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} else {
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None
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}
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},
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hir::ExprKind::Struct(ref path, ref fields, None) => {
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if match_qpath(path, &paths::RANGE_FROM_STD) || match_qpath(path, &paths::RANGE_FROM) {
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Some(Range {
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start: Some(get_field("start", fields)?),
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end: None,
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limits: ast::RangeLimits::HalfOpen,
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})
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} else if match_qpath(path, &paths::RANGE_STD) || match_qpath(path, &paths::RANGE) {
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Some(Range {
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start: Some(get_field("start", fields)?),
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end: Some(get_field("end", fields)?),
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limits: ast::RangeLimits::HalfOpen,
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})
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} else if match_qpath(path, &paths::RANGE_TO_INCLUSIVE_STD) || match_qpath(path, &paths::RANGE_TO_INCLUSIVE)
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{
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Some(Range {
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start: None,
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end: Some(get_field("end", fields)?),
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limits: ast::RangeLimits::Closed,
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})
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} else if match_qpath(path, &paths::RANGE_TO_STD) || match_qpath(path, &paths::RANGE_TO) {
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Some(Range {
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start: None,
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end: Some(get_field("end", fields)?),
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limits: ast::RangeLimits::HalfOpen,
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})
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} else {
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None
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}
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},
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_ => None,
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}
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}
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/// Checks if a `let` statement is from a `for` loop desugaring.
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pub fn is_from_for_desugar(local: &hir::Local<'_>) -> bool {
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// This will detect plain for-loops without an actual variable binding:
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//
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// ```
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// for x in some_vec {
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// // do stuff
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// }
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// ```
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if_chain! {
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if let Some(ref expr) = local.init;
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if let hir::ExprKind::Match(_, _, hir::MatchSource::ForLoopDesugar) = expr.kind;
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then {
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return true;
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}
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}
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// This detects a variable binding in for loop to avoid `let_unit_value`
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// lint (see issue #1964).
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//
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// ```
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// for _ in vec![()] {
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// // anything
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// }
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// ```
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if let hir::LocalSource::ForLoopDesugar = local.source {
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return true;
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}
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false
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}
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/// Recover the essential nodes of a desugared for loop:
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/// `for pat in arg { body }` becomes `(pat, arg, body)`.
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pub fn for_loop<'tcx>(
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expr: &'tcx hir::Expr<'tcx>,
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) -> Option<(&hir::Pat<'_>, &'tcx hir::Expr<'tcx>, &'tcx hir::Expr<'tcx>)> {
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if_chain! {
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if let hir::ExprKind::Match(ref iterexpr, ref arms, hir::MatchSource::ForLoopDesugar) = expr.kind;
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if let hir::ExprKind::Call(_, ref iterargs) = iterexpr.kind;
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if iterargs.len() == 1 && arms.len() == 1 && arms[0].guard.is_none();
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if let hir::ExprKind::Loop(ref block, _, _) = arms[0].body.kind;
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if block.expr.is_none();
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if let [ _, _, ref let_stmt, ref body ] = *block.stmts;
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if let hir::StmtKind::Local(ref local) = let_stmt.kind;
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if let hir::StmtKind::Expr(ref expr) = body.kind;
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then {
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return Some((&*local.pat, &iterargs[0], expr));
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}
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}
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None
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}
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/// Recover the essential nodes of a desugared while loop:
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/// `while cond { body }` becomes `(cond, body)`.
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pub fn while_loop<'tcx>(expr: &'tcx hir::Expr<'tcx>) -> Option<(&'tcx hir::Expr<'tcx>, &'tcx hir::Expr<'tcx>)> {
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if_chain! {
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if let hir::ExprKind::Loop(block, _, hir::LoopSource::While) = &expr.kind;
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if let hir::Block { expr: Some(expr), .. } = &**block;
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if let hir::ExprKind::Match(cond, arms, hir::MatchSource::WhileDesugar) = &expr.kind;
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if let hir::ExprKind::DropTemps(cond) = &cond.kind;
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if let [arm, ..] = &arms[..];
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if let hir::Arm { body, .. } = arm;
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then {
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return Some((cond, body));
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}
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}
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None
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}
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/// Recover the essential nodes of a desugared if block
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/// `if cond { then } else { els }` becomes `(cond, then, Some(els))`
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pub fn if_block<'tcx>(
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expr: &'tcx hir::Expr<'tcx>,
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) -> Option<(
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&'tcx hir::Expr<'tcx>,
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&'tcx hir::Expr<'tcx>,
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Option<&'tcx hir::Expr<'tcx>>,
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)> {
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if let hir::ExprKind::Match(ref cond, ref arms, hir::MatchSource::IfDesugar { contains_else_clause }) = expr.kind {
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let cond = if let hir::ExprKind::DropTemps(ref cond) = cond.kind {
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cond
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} else {
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panic!("If block desugar must contain DropTemps");
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};
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let then = &arms[0].body;
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let els = if contains_else_clause {
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Some(&*arms[1].body)
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} else {
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None
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};
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Some((cond, then, els))
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} else {
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None
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}
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}
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/// Represent the pre-expansion arguments of a `vec!` invocation.
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pub enum VecArgs<'a> {
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/// `vec![elem; len]`
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Repeat(&'a hir::Expr<'a>, &'a hir::Expr<'a>),
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/// `vec![a, b, c]`
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Vec(&'a [hir::Expr<'a>]),
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}
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/// Returns the arguments of the `vec!` macro if this expression was expanded
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/// from `vec!`.
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pub fn vec_macro<'e>(cx: &LateContext<'_, '_>, expr: &'e hir::Expr<'_>) -> Option<VecArgs<'e>> {
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if_chain! {
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if let hir::ExprKind::Call(ref fun, ref args) = expr.kind;
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if let hir::ExprKind::Path(ref qpath) = fun.kind;
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if is_expn_of(fun.span, "vec").is_some();
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if let Some(fun_def_id) = cx.tables.qpath_res(qpath, fun.hir_id).opt_def_id();
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then {
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return if match_def_path(cx, fun_def_id, &paths::VEC_FROM_ELEM) && args.len() == 2 {
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// `vec![elem; size]` case
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Some(VecArgs::Repeat(&args[0], &args[1]))
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}
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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
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if_chain! {
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if let hir::ExprKind::Box(ref boxed) = args[0].kind;
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if let hir::ExprKind::Array(ref args) = boxed.kind;
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then {
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return Some(VecArgs::Vec(&*args));
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}
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}
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None
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}
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else {
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None
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};
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}
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}
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None
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}
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