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resolve: bool -> enum PatBoundCtx

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This commit is contained in:
Mazdak Farrokhzad 2019-09-05 01:43:53 +02:00
parent a7db1a4861
commit 0341b78044
1 changed files with 29 additions and 18 deletions
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47
src/librustc_resolve/late.rs
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@ -75,6 +75,16 @@ impl PatternSource {
}
}
/// Denotes whether the context for the set of already bound bindings is a `Product`
/// or `Or` context. This is used in e.g., `fresh_binding` and `resolve_pattern_inner`.
/// See those functions for more information.
enum PatBoundCtx {
/// A product pattern context, e.g., `Variant(a, b)`.
Product,
/// An or-pattern context, e.g., `p_0 | ... | p_n`.
Or,
}
/// The rib kind restricts certain accesses,
/// e.g. to a `Res::Local` of an outer item.
#[derive(Copy, Clone, Debug)]
@ -1109,7 +1119,7 @@ impl<'a, 'b> LateResolutionVisitor<'a, '_> {
}
fn resolve_params(&mut self, params: &[Param]) {
let mut bindings = smallvec![(false, Default::default())];
let mut bindings = smallvec![(PatBoundCtx::Product, Default::default())];
for Param { pat, ty, .. } in params {
self.resolve_pattern(pat, PatternSource::FnParam, &mut bindings);
self.visit_ty(ty);
@ -1255,14 +1265,15 @@ impl<'a, 'b> LateResolutionVisitor<'a, '_> {
/// Arising from `source`, resolve a top level pattern.
fn resolve_pattern_top(&mut self, pat: &Pat, pat_src: PatternSource) {
self.resolve_pattern(pat, pat_src, &mut smallvec![(false, Default::default())]);
let mut bindings = smallvec![(PatBoundCtx::Product, Default::default())];
self.resolve_pattern(pat, pat_src, &mut bindings);
}
fn resolve_pattern(
&mut self,
pat: &Pat,
pat_src: PatternSource,
bindings: &mut SmallVec<[(bool, FxHashSet<Ident>); 1]>,
bindings: &mut SmallVec<[(PatBoundCtx, FxHashSet<Ident>); 1]>,
) {
self.resolve_pattern_inner(pat, pat_src, bindings);
// This has to happen *after* we determine which pat_idents are variants:
@ -1276,15 +1287,15 @@ impl<'a, 'b> LateResolutionVisitor<'a, '_> {
///
/// A stack of sets of bindings accumulated.
///
/// In each set, `false` denotes that a found binding in it should be interpreted as
/// re-binding an already bound binding. This results in an error. Meanwhile, `true`
/// denotes that a found binding in the set should result in reusing this binding
/// rather than creating a fresh one. In other words, `false` and `true` correspond
/// to product (e.g., `(a, b)`) and sum/or contexts (e.g., `p_0 | ... | p_i`) respectively.
/// In each set, `PatBoundCtx::Product` denotes that a found binding in it should
/// be interpreted as re-binding an already bound binding. This results in an error.
/// Meanwhile, `PatBound::Or` denotes that a found binding in the set should result
/// in reusing this binding rather than creating a fresh one.
///
/// When called at the top level, the stack should have a single element with `false`.
/// Otherwise, pushing to the stack happens as or-patterns are encountered and the
/// context needs to be switched to `true` and then `false` for each `p_i.
/// When called at the top level, the stack must have a single element
/// with `PatBound::Product`. Otherwise, pushing to the stack happens as
/// or-patterns (`p_0 | ... | p_n`) are encountered and the context needs
/// to be switched to `PatBoundCtx::Or` and then `PatBoundCtx::Product` for each `p_i`.
/// When each `p_i` has been dealt with, the top set is merged with its parent.
/// When a whole or-pattern has been dealt with, the thing happens.
///
@ -1293,7 +1304,7 @@ impl<'a, 'b> LateResolutionVisitor<'a, '_> {
&mut self,
pat: &Pat,
pat_src: PatternSource,
bindings: &mut SmallVec<[(bool, FxHashSet<Ident>); 1]>,
bindings: &mut SmallVec<[(PatBoundCtx, FxHashSet<Ident>); 1]>,
) {
// Visit all direct subpatterns of this pattern.
pat.walk(&mut |pat| {
@ -1317,15 +1328,15 @@ impl<'a, 'b> LateResolutionVisitor<'a, '_> {
self.smart_resolve_path(pat.id, None, path, PathSource::Struct);
}
PatKind::Or(ref ps) => {
// Add a new set of bindings to the stack. `true` here records that when a
// Add a new set of bindings to the stack. `Or` here records that when a
// binding already exists in this set, it should not result in an error because
// `V1(a) | V2(a)` must be allowed and are checked for consistency later.
bindings.push((true, Default::default()));
bindings.push((PatBoundCtx::Or, Default::default()));
for p in ps {
// Now we need to switch back to a product context so that each
// part of the or-pattern internally rejects already bound names.
// For example, `V1(a) | V2(a, a)` and `V1(a, a) | V2(a)` are bad.
bindings.push((false, Default::default()));
bindings.push((PatBoundCtx::Product, Default::default()));
self.resolve_pattern_inner(p, pat_src, bindings);
// Move up the non-overlapping bindings to the or-pattern.
// Existing bindings just get "merged".
@ -1352,7 +1363,7 @@ impl<'a, 'b> LateResolutionVisitor<'a, '_> {
ident: Ident,
pat_id: NodeId,
pat_src: PatternSource,
bindings: &mut SmallVec<[(bool, FxHashSet<Ident>); 1]>,
bindings: &mut SmallVec<[(PatBoundCtx, FxHashSet<Ident>); 1]>,
) -> Res {
// Add the binding to the local ribs, if it doesn't already exist in the bindings map.
// (We must not add it if it's in the bindings map because that breaks the assumptions
@ -1366,10 +1377,10 @@ impl<'a, 'b> LateResolutionVisitor<'a, '_> {
for (is_sum, set) in bindings.iter_mut().rev() {
match (is_sum, set.get(&ident).cloned()) {
// Already bound in a product pattern, e.g. `(a, a)` which is not allowed.
(false, Some(..)) => already_bound_and = true,
(PatBoundCtx::Product, Some(..)) => already_bound_and = true,
// Already bound in an or-pattern, e.g. `V1(a) | V2(a)`.
// This is *required* for consistency which is checked later.
(true, Some(..)) => already_bound_or = true,
(PatBoundCtx::Or, Some(..)) => already_bound_or = true,
// Not already bound here.
_ => {}
}