Skip to content

Guard HIR lowered contracts with contract_checks #144438

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
wants to merge 1 commit into
base: master
Choose a base branch
from
+459 −120
Open

Guard HIR lowered contracts with contract_checks #144438

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
260 changes: 260 additions & 0 deletions compiler/rustc_ast_lowering/src/contract.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,260 @@
use crate::LoweringContext;

impl<'a, 'hir> LoweringContext<'a, 'hir> {
pub(super) fn lower_contract(
&mut self,
body: impl FnOnce(&mut Self) -> rustc_hir::Expr<'hir>,
contract: &rustc_ast::FnContract,
) -> rustc_hir::Expr<'hir> {
match (&contract.requires, &contract.ensures) {
(Some(req), Some(ens)) => {
// Lower the fn contract, which turns:
//
// { body }
//
// into:
//
// {
// let __postcond = if contracts_checks() {
// contract_check_requires(PRECOND);
// Some(|ret_val| POSTCOND)
// } else {
// None
// };
// contract_check_ensures(__postcond, { body })
// }

let precond = self.lower_precond(req);
let postcond_checker = self.lower_postcond_checker(ens);

let contract_check =
self.lower_contract_check_with_postcond(Some(precond), postcond_checker);

let wrapped_body =
self.wrap_body_with_contract_check(body, contract_check, postcond_checker.span);
self.expr_block(wrapped_body)
}
(None, Some(ens)) => {
// Lower the fn contract, which turns:
//
// { body }
//
// into:
//
// {
// let __postcond = if contracts_check() {
// Some(|ret_val| POSTCOND)
// } else {
// None
// };
// __postcond({ body })
// }

let postcond_checker = self.lower_postcond_checker(ens);
let contract_check =
self.lower_contract_check_with_postcond(None, postcond_checker);

let wrapped_body =
self.wrap_body_with_contract_check(body, contract_check, postcond_checker.span);
self.expr_block(wrapped_body)
}
(Some(req), None) => {
// Lower the fn contract, which turns:
//
// { body }
//
// into:
//
// {
// if contracts_check() {
// contract_requires(PRECOND);
// }
// body
// }
let precond = self.lower_precond(req);
let precond_check = self.lower_contract_check_just_precond(precond);

let body = self.arena.alloc(body(self));

// Flatten the body into precond check, then body.
let wrapped_body = self.block_all(
body.span,
self.arena.alloc_from_iter([precond_check].into_iter()),
Some(body),
);
self.expr_block(wrapped_body)
}
(None, None) => body(self),
}
}

/// Lower the precondition check intrinsic.
fn lower_precond(&mut self, req: &Box<rustc_ast::Expr>) -> rustc_hir::Stmt<'hir> {
let lowered_req = self.lower_expr_mut(&req);
let req_span = self.mark_span_with_reason(
rustc_span::DesugaringKind::Contract,
lowered_req.span,
None,
);
let precond = self.expr_call_lang_item_fn_mut(
req_span,
rustc_hir::LangItem::ContractCheckRequires,
&*arena_vec![self; lowered_req],
);
self.stmt_expr(req.span, precond)
}

fn lower_postcond_checker(
&mut self,
ens: &Box<rustc_ast::Expr>,
) -> &'hir rustc_hir::Expr<'hir> {
let ens_span = self.lower_span(ens.span);
let ens_span =
self.mark_span_with_reason(rustc_span::DesugaringKind::Contract, ens_span, None);
let lowered_ens = self.lower_expr_mut(&ens);
self.expr_call_lang_item_fn(
ens_span,
rustc_hir::LangItem::ContractBuildCheckEnsures,
&*arena_vec![self; lowered_ens],
)
}

fn lower_contract_check_just_precond(
&mut self,
precond: rustc_hir::Stmt<'hir>,
) -> rustc_hir::Stmt<'hir> {
let stmts = self.arena.alloc_from_iter([precond].into_iter());

let then_block_stmts = self.block_all(precond.span, stmts, None);
let then_block = self.arena.alloc(self.expr_block(&then_block_stmts));

let precond_check = rustc_hir::ExprKind::If(
self.expr_call_lang_item_fn(
precond.span,
rustc_hir::LangItem::ContractChecks,
Default::default(),
),
then_block,
None,
);

let precond_check = self.expr(precond.span, precond_check);
self.stmt_expr(precond.span, precond_check)
}

fn lower_contract_check_with_postcond(
&mut self,
precond: Option<rustc_hir::Stmt<'hir>>,
postcond_checker: &'hir rustc_hir::Expr<'hir>,
) -> &'hir rustc_hir::Expr<'hir> {
let stmts = self.arena.alloc_from_iter(precond.into_iter());
let span = match precond {
Some(precond) => precond.span,
None => postcond_checker.span,
};

let postcond_checker = self.arena.alloc(self.expr_enum_variant_lang_item(
postcond_checker.span,
rustc_hir::lang_items::LangItem::OptionSome,
&*arena_vec![self; *postcond_checker],
));
let then_block_stmts = self.block_all(span, stmts, Some(postcond_checker));
let then_block = self.arena.alloc(self.expr_block(&then_block_stmts));

let none_expr = self.arena.alloc(self.expr_enum_variant_lang_item(
postcond_checker.span,
rustc_hir::lang_items::LangItem::OptionNone,
Default::default(),
));
let else_block = self.block_expr(none_expr);
let else_block = self.arena.alloc(self.expr_block(else_block));

let contract_check = rustc_hir::ExprKind::If(
self.expr_call_lang_item_fn(
span,
rustc_hir::LangItem::ContractChecks,
Default::default(),
),
then_block,
Some(else_block),
);
self.arena.alloc(self.expr(span, contract_check))
}

fn wrap_body_with_contract_check(
&mut self,
body: impl FnOnce(&mut Self) -> rustc_hir::Expr<'hir>,
contract_check: &'hir rustc_hir::Expr<'hir>,
postcond_span: rustc_span::Span,
) -> &'hir rustc_hir::Block<'hir> {
let check_ident: rustc_span::Ident =
rustc_span::Ident::from_str_and_span("__ensures_checker", postcond_span);
let (check_hir_id, postcond_decl) = {
// Set up the postcondition `let` statement.
let (checker_pat, check_hir_id) = self.pat_ident_binding_mode_mut(
postcond_span,
check_ident,
rustc_hir::BindingMode::NONE,
);
(
check_hir_id,
self.stmt_let_pat(
None,
postcond_span,
Some(contract_check),
self.arena.alloc(checker_pat),
rustc_hir::LocalSource::Contract,
),
)
};

// Install contract_ensures so we will intercept `return` statements,
// then lower the body.
self.contract_ensures = Some((postcond_span, check_ident, check_hir_id));
let body = self.arena.alloc(body(self));

// Finally, inject an ensures check on the implicit return of the body.
let body = self.inject_ensures_check(body, postcond_span, check_ident, check_hir_id);

// Flatten the body into precond, then postcond, then wrapped body.
let wrapped_body = self.block_all(
body.span,
self.arena.alloc_from_iter([postcond_decl].into_iter()),
Some(body),
);
wrapped_body
}

/// Create an `ExprKind::Ret` that is optionally wrapped by a call to check
/// a contract ensures clause, if it exists.
pub(super) fn checked_return(
&mut self,
opt_expr: Option<&'hir rustc_hir::Expr<'hir>>,
) -> rustc_hir::ExprKind<'hir> {
let checked_ret =
if let Some((check_span, check_ident, check_hir_id)) = self.contract_ensures {
let expr = opt_expr.unwrap_or_else(|| self.expr_unit(check_span));
Some(self.inject_ensures_check(expr, check_span, check_ident, check_hir_id))
} else {
opt_expr
};
rustc_hir::ExprKind::Ret(checked_ret)
}

/// Wraps an expression with a call to the ensures check before it gets returned.
pub(super) fn inject_ensures_check(
&mut self,
expr: &'hir rustc_hir::Expr<'hir>,
span: rustc_span::Span,
cond_ident: rustc_span::Ident,
cond_hir_id: rustc_hir::HirId,
) -> &'hir rustc_hir::Expr<'hir> {
let cond_fn = self.expr_ident(span, cond_ident, cond_hir_id);
let call_expr = self.expr_call_lang_item_fn_mut(
span,
rustc_hir::LangItem::ContractCheckEnsures,
arena_vec![self; *cond_fn, *expr],
);
self.arena.alloc(call_expr)
}
}
86 changes: 53 additions & 33 deletions compiler/rustc_ast_lowering/src/expr.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -380,36 +380,6 @@ impl<'hir> LoweringContext<'_, 'hir> {
})
}

/// Create an `ExprKind::Ret` that is optionally wrapped by a call to check
/// a contract ensures clause, if it exists.
fn checked_return(&mut self, opt_expr: Option<&'hir hir::Expr<'hir>>) -> hir::ExprKind<'hir> {
let checked_ret =
if let Some((check_span, check_ident, check_hir_id)) = self.contract_ensures {
let expr = opt_expr.unwrap_or_else(|| self.expr_unit(check_span));
Some(self.inject_ensures_check(expr, check_span, check_ident, check_hir_id))
} else {
opt_expr
};
hir::ExprKind::Ret(checked_ret)
}

/// Wraps an expression with a call to the ensures check before it gets returned.
pub(crate) fn inject_ensures_check(
&mut self,
expr: &'hir hir::Expr<'hir>,
span: Span,
cond_ident: Ident,
cond_hir_id: HirId,
) -> &'hir hir::Expr<'hir> {
let cond_fn = self.expr_ident(span, cond_ident, cond_hir_id);
let call_expr = self.expr_call_lang_item_fn_mut(
span,
hir::LangItem::ContractCheckEnsures,
arena_vec![self; *cond_fn, *expr],
);
self.arena.alloc(call_expr)
}

pub(crate) fn lower_const_block(&mut self, c: &AnonConst) -> hir::ConstBlock {
self.with_new_scopes(c.value.span, |this| {
let def_id = this.local_def_id(c.id);
Expand Down Expand Up @@ -2095,7 +2065,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
self.expr(span, hir::ExprKind::AddrOf(hir::BorrowKind::Ref, hir::Mutability::Mut, e))
}

fn expr_unit(&mut self, sp: Span) -> &'hir hir::Expr<'hir> {
pub(super) fn expr_unit(&mut self, sp: Span) -> &'hir hir::Expr<'hir> {
self.arena.alloc(self.expr(sp, hir::ExprKind::Tup(&[])))
}

Expand Down Expand Up @@ -2133,6 +2103,43 @@ impl<'hir> LoweringContext<'_, 'hir> {
self.expr(span, hir::ExprKind::Call(e, args))
}

pub(super) fn expr_struct(
&mut self,
span: Span,
path: &'hir hir::QPath<'hir>,
fields: &'hir [hir::ExprField<'hir>],
) -> hir::Expr<'hir> {
self.expr(span, hir::ExprKind::Struct(path, fields, rustc_hir::StructTailExpr::None))
}

pub(super) fn expr_enum_variant(
&mut self,
span: Span,
path: &'hir hir::QPath<'hir>,
fields: &'hir [hir::Expr<'hir>],
) -> hir::Expr<'hir> {
let fields = self.arena.alloc_from_iter(fields.into_iter().enumerate().map(|(i, f)| {
hir::ExprField {
hir_id: self.next_id(),
ident: Ident::from_str(&i.to_string()),
expr: f,
span: f.span,
is_shorthand: false,
}
}));
self.expr_struct(span, path, fields)
}

pub(super) fn expr_enum_variant_lang_item(
&mut self,
span: Span,
lang_item: hir::LangItem,
fields: &'hir [hir::Expr<'hir>],
) -> hir::Expr<'hir> {
let path = self.arena.alloc(self.lang_item_path(span, lang_item));
self.expr_enum_variant(span, path, fields)
}

pub(super) fn expr_call(
&mut self,
span: Span,
Expand Down Expand Up @@ -2161,8 +2168,21 @@ impl<'hir> LoweringContext<'_, 'hir> {
self.arena.alloc(self.expr_call_lang_item_fn_mut(span, lang_item, args))
}

fn expr_lang_item_path(&mut self, span: Span, lang_item: hir::LangItem) -> hir::Expr<'hir> {
self.expr(span, hir::ExprKind::Path(hir::QPath::LangItem(lang_item, self.lower_span(span))))
pub(super) fn expr_lang_item_path(
&mut self,
span: Span,
lang_item: hir::LangItem,
) -> hir::Expr<'hir> {
let path = self.lang_item_path(span, lang_item);
self.expr(span, hir::ExprKind::Path(path))
}

pub(super) fn lang_item_path(
&mut self,
span: Span,
lang_item: hir::LangItem,
) -> hir::QPath<'hir> {
hir::QPath::LangItem(lang_item, self.lower_span(span))
}

/// `<LangItem>::name`
Expand Down
Loading
Loading