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//! This module provides a pass that removes parts of MIR that are no longer relevant after
//! analysis phase and borrowck. In particular, it removes false edges, user type annotations and
//! replaces following statements with [`Nop`]s:
//!
//! - [`AscribeUserType`]
//! - [`FakeRead`]
//! - [`Assign`] statements with a [`Shallow`] borrow
//!
//! [`AscribeUserType`]: rustc_middle::mir::StatementKind::AscribeUserType
//! [`Assign`]: rustc_middle::mir::StatementKind::Assign
//! [`FakeRead`]: rustc_middle::mir::StatementKind::FakeRead
//! [`Nop`]: rustc_middle::mir::StatementKind::Nop
//! [`Shallow`]: rustc_middle::mir::BorrowKind::Shallow
use crate::MirPass;
use rustc_middle::mir::{Body, BorrowKind, Rvalue, StatementKind, TerminatorKind};
use rustc_middle::ty::TyCtxt;
pub struct CleanupPostBorrowck;
impl<'tcx> MirPass<'tcx> for CleanupPostBorrowck {
fn run_pass(&self, _tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
for basic_block in body.basic_blocks.as_mut() {
for statement in basic_block.statements.iter_mut() {
match statement.kind {
StatementKind::AscribeUserType(..)
| StatementKind::Assign(box (_, Rvalue::Ref(_, BorrowKind::Shallow, _)))
| StatementKind::FakeRead(..) => statement.make_nop(),
_ => (),
}
}
let terminator = basic_block.terminator_mut();
match terminator.kind {
TerminatorKind::FalseEdge { real_target, .. }
| TerminatorKind::FalseUnwind { real_target, .. } => {
terminator.kind = TerminatorKind::Goto { target: real_target };
}
_ => {}
}
}
body.user_type_annotations.raw.clear();
for decl in &mut body.local_decls {
decl.user_ty = None;
}
}
}
|
