rust-lang/rust
1
0
Fork 0
Code Issues Pull Requests Actions 1 Packages Projects Releases Wiki Activity

Lower condition directly from AST to HIR

Browse Source
This commit is contained in:
Nathan Whitaker
2022-10-13 18:20:39 -07:00
parent ad8b242724
commit 709a08ade6
1 changed files with 24 additions and 22 deletions
Download Patch File Download Diff File Expand all files Collapse all files

46
compiler/rustc_ast_lowering/src/expr.rs
View File

@@ -387,23 +387,26 @@ impl<'hir> LoweringContext<'_, 'hir> {
then: &Block,
else_opt: Option<&Expr>,
) -> hir::ExprKind<'hir> {
let lowered_cond = self.lower_expr(cond);
let new_cond = self.wrap_cond_in_drop_scope(lowered_cond);
let lowered_cond = self.lower_cond(cond);
let then_expr = self.lower_block_expr(then);
if let Some(rslt) = else_opt {
hir::ExprKind::If(new_cond, self.arena.alloc(then_expr), Some(self.lower_expr(rslt)))
hir::ExprKind::If(
lowered_cond,
self.arena.alloc(then_expr),
Some(self.lower_expr(rslt)),
)
} else {
hir::ExprKind::If(new_cond, self.arena.alloc(then_expr), None)
hir::ExprKind::If(lowered_cond, self.arena.alloc(then_expr), None)
}
}
// Wraps a condition (i.e. `cond` in `if cond` or `while cond`) in a terminating scope
// Lowers a condition (i.e. `cond` in `if cond` or `while cond`), wrapping it in a terminating scope
// so that temporaries created in the condition don't live beyond it.
fn wrap_cond_in_drop_scope(&mut self, cond: &'hir hir::Expr<'hir>) -> &'hir hir::Expr<'hir> {
fn has_let_expr<'hir>(expr: &'hir hir::Expr<'hir>) -> bool {
match expr.kind {
hir::ExprKind::Binary(_, lhs, rhs) => has_let_expr(lhs) || has_let_expr(rhs),
hir::ExprKind::Let(..) => true,
fn lower_cond(&mut self, cond: &Expr) -> &'hir hir::Expr<'hir> {
fn has_let_expr(expr: &Expr) -> bool {
match &expr.kind {
ExprKind::Binary(_, lhs, rhs) => has_let_expr(lhs) || has_let_expr(rhs),
ExprKind::Let(..) => true,
_ => false,
}
}
@@ -415,14 +418,13 @@ impl<'hir> LoweringContext<'_, 'hir> {
// In order to mantain the drop behavior for the non `let` parts of the condition,
// we still wrap them in terminating scopes, e.g. `if foo && let pat = val` essentially
// gets transformed into `if { let _t = foo; _t } && let pat = val`
match cond.kind {
hir::ExprKind::Binary(
op @ Spanned { node: hir::BinOpKind::And | hir::BinOpKind::Or, .. },
lhs,
rhs,
) if has_let_expr(cond) => {
let lhs = self.wrap_cond_in_drop_scope(lhs);
let rhs = self.wrap_cond_in_drop_scope(rhs);
match &cond.kind {
ExprKind::Binary(op @ Spanned { node: ast::BinOpKind::And, .. }, lhs, rhs)
if has_let_expr(cond) =>
{
let op = self.lower_binop(*op);
let lhs = self.lower_cond(lhs);
let rhs = self.lower_cond(rhs);
self.arena.alloc(self.expr(
cond.span,
@@ -430,8 +432,9 @@ impl<'hir> LoweringContext<'_, 'hir> {
AttrVec::new(),
))
}
hir::ExprKind::Let(_) => cond,
ExprKind::Let(..) => self.lower_expr(cond),
_ => {
let cond = self.lower_expr(cond);
let reason = DesugaringKind::CondTemporary;
let span_block = self.mark_span_with_reason(reason, cond.span, None);
self.expr_drop_temps(span_block, cond, AttrVec::new())
@@ -462,14 +465,13 @@ impl<'hir> LoweringContext<'_, 'hir> {
body: &Block,
opt_label: Option<Label>,
) -> hir::ExprKind<'hir> {
let lowered_cond = self.with_loop_condition_scope(|t| t.lower_expr(cond));
let new_cond = self.wrap_cond_in_drop_scope(lowered_cond);
let lowered_cond = self.with_loop_condition_scope(|t| t.lower_cond(cond));
let then = self.lower_block_expr(body);
let expr_break = self.expr_break(span, AttrVec::new());
let stmt_break = self.stmt_expr(span, expr_break);
let else_blk = self.block_all(span, arena_vec![self; stmt_break], None);
let else_expr = self.arena.alloc(self.expr_block(else_blk, AttrVec::new()));
let if_kind = hir::ExprKind::If(new_cond, self.arena.alloc(then), Some(else_expr));
let if_kind = hir::ExprKind::If(lowered_cond, self.arena.alloc(then), Some(else_expr));
let if_expr = self.expr(span, if_kind, AttrVec::new());
let block = self.block_expr(self.arena.alloc(if_expr));
let span = self.lower_span(span.with_hi(cond.span.hi()));