bjoernager/rust
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Reintroduce hir::ExprKind::If

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This commit is contained in:
Caio 2021-01-01 15:38:11 -03:00
parent c8915eebea
commit f85fc264fe
97 changed files with 1046 additions and 787 deletions
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56
compiler/rustc_ast_lowering/src/expr.rs
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@ -87,9 +87,12 @@ impl<'hir> LoweringContext<'_, 'hir> {
ExprKind::Let(ref pat, ref scrutinee) => {
self.lower_expr_let(e.span, pat, scrutinee)
}
ExprKind::If(ref cond, ref then, ref else_opt) => {
self.lower_expr_if(e.span, cond, then, else_opt.as_deref())
}
ExprKind::If(ref cond, ref then, ref else_opt) => match cond.kind {
ExprKind::Let(ref pat, ref scrutinee) => {
self.lower_expr_if_let(e.span, pat, scrutinee, then, else_opt.as_deref())
}
_ => self.lower_expr_if(cond, then, else_opt.as_deref()),
},
ExprKind::While(ref cond, ref body, opt_label) => self
.with_loop_scope(e.id, |this| {
this.lower_expr_while_in_loop_scope(e.span, cond, body, opt_label)
@ -337,10 +340,30 @@ impl<'hir> LoweringContext<'_, 'hir> {
fn lower_expr_if(
&mut self,
span: Span,
cond: &Expr,
then: &Block,
else_opt: Option<&Expr>,
) -> hir::ExprKind<'hir> {
macro_rules! make_if {
($opt:expr) => {{
let then_expr = self.lower_block_expr(then);
hir::ExprKind::If(self.lower_expr(cond), self.arena.alloc(then_expr), $opt)
}};
}
if let Some(rslt) = else_opt {
make_if!(Some(self.lower_expr(rslt)))
} else {
make_if!(None)
}
}
fn lower_expr_if_let(
&mut self,
span: Span,
pat: &Pat,
scrutinee: &Expr,
then: &Block,
else_opt: Option<&Expr>,
) -> hir::ExprKind<'hir> {
// FIXME(#53667): handle lowering of && and parens.
@ -353,30 +376,13 @@ impl<'hir> LoweringContext<'_, 'hir> {
let else_arm = self.arm(else_pat, else_expr);
// Handle then + scrutinee:
let (then_pat, scrutinee, desugar) = match cond.kind {
// `<pat> => <then>`:
ExprKind::Let(ref pat, ref scrutinee) => {
let scrutinee = self.lower_expr(scrutinee);
let pat = self.lower_pat(pat);
(pat, scrutinee, hir::MatchSource::IfLetDesugar { contains_else_clause })
}
// `true => <then>`:
_ => {
// Lower condition:
let cond = self.lower_expr(cond);
let span_block =
self.mark_span_with_reason(DesugaringKind::CondTemporary, cond.span, None);
// Wrap in a construct equivalent to `{ let _t = $cond; _t }`
// to preserve drop semantics since `if cond { ... }` does not
// let temporaries live outside of `cond`.
let cond = self.expr_drop_temps(span_block, cond, ThinVec::new());
let pat = self.pat_bool(span, true);
(pat, cond, hir::MatchSource::IfDesugar { contains_else_clause })
}
};
let scrutinee = self.lower_expr(scrutinee);
let then_pat = self.lower_pat(pat);
let then_expr = self.lower_block_expr(then);
let then_arm = self.arm(then_pat, self.arena.alloc(then_expr));
let desugar = hir::MatchSource::IfLetDesugar { contains_else_clause };
hir::ExprKind::Match(scrutinee, arena_vec![self; then_arm, else_arm], desugar)
}