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Handle break somewhat better

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Still no break-with-value or labels, but at least we know that `loop { break; }`
doesn't diverge.
This commit is contained in:
Florian Diebold 2020-05-08 17:59:58 +02:00
parent fe7bf993aa
commit b60970fd20
3 changed files with 105 additions and 3 deletions
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29
crates/ra_hir_ty/src/infer/expr.rs
View file

@ -21,7 +21,10 @@ use crate::{
Ty, TypeCtor, Uncertain,
};
use super::{BindingMode, Expectation, InferenceContext, InferenceDiagnostic, TypeMismatch, Diverges};
use super::{
BindingMode, BreakableContext, Diverges, Expectation, InferenceContext, InferenceDiagnostic,
TypeMismatch,
};
impl<'a> InferenceContext<'a> {
pub(super) fn infer_expr(&mut self, tgt_expr: ExprId, expected: &Expectation) -> Ty {
@ -90,24 +93,43 @@ impl<'a> InferenceContext<'a> {
Ty::Unknown
}
Expr::Loop { body } => {
self.breakables.push(BreakableContext { may_break: false });
self.infer_expr(*body, &Expectation::has_type(Ty::unit()));
let ctxt = self.breakables.pop().expect("breakable stack broken");
if ctxt.may_break {
self.diverges = Diverges::Maybe;
}
// FIXME handle break with value
Ty::simple(TypeCtor::Never)
if ctxt.may_break {
Ty::unit()
} else {
Ty::simple(TypeCtor::Never)
}
}
Expr::While { condition, body } => {
self.breakables.push(BreakableContext { may_break: false });
// while let is desugared to a match loop, so this is always simple while
self.infer_expr(*condition, &Expectation::has_type(Ty::simple(TypeCtor::Bool)));
self.infer_expr(*body, &Expectation::has_type(Ty::unit()));
let _ctxt = self.breakables.pop().expect("breakable stack broken");
// the body may not run, so it diverging doesn't mean we diverge
self.diverges = Diverges::Maybe;
Ty::unit()
}
Expr::For { iterable, body, pat } => {
let iterable_ty = self.infer_expr(*iterable, &Expectation::none());
self.breakables.push(BreakableContext { may_break: false });
let pat_ty =
self.resolve_associated_type(iterable_ty, self.resolve_into_iter_item());
self.infer_pat(*pat, &pat_ty, BindingMode::default());
self.infer_expr(*body, &Expectation::has_type(Ty::unit()));
let _ctxt = self.breakables.pop().expect("breakable stack broken");
// the body may not run, so it diverging doesn't mean we diverge
self.diverges = Diverges::Maybe;
Ty::unit()
}
Expr::Lambda { body, args, ret_type, arg_types } => {
@ -211,6 +233,9 @@ impl<'a> InferenceContext<'a> {
// FIXME handle break with value
self.infer_expr(*expr, &Expectation::none());
}
if let Some(ctxt) = self.breakables.last_mut() {
ctxt.may_break = true;
}
Ty::simple(TypeCtor::Never)
}
Expr::Return { expr } => {