Add a variant to fallback_to_outer

Nadrieril · Jan 18, 2025 · 4dc2368 · 4dc2368
1 parent 816737b
commit 4dc2368
Show file tree

Hide file tree

Showing 120 changed files with 212 additions and 160 deletions.
diff --git a/src/ast/printer.rs b/src/ast/printer.rs
@@ -346,10 +346,9 @@ impl Rule {
             extras.push(format!("{x:?}"))
         }
         if let Deref(_, _, x) = *self
-            && options.fallback_to_outer
-            && x == FallbackToOuter(true)
+            && x != FallbackToOuter(FallbackToOuterBehavior::No)
         {
-            extras.push(format!("FallbackToOuter"))
+            extras.push(format!("FallbackToOuter({:?})", x.0))
         }
 
         let mut out = variant_name.to_string();

diff --git a/src/rulesets/ty_based.rs b/src/rulesets/ty_based.rs
@@ -44,6 +44,20 @@ pub enum InheritedRefOnRefBehavior {
     Error,
 }
 
+/// In `InheritedRefOnRefBehavior::EatBoth` or `EatInner` modes, what to do if a reference pattern
+/// fails to match against an underlying place of reference type.
+#[derive(
+    Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Serialize, Deserialize, Encode, Decode,
+)]
+pub enum FallbackToOuterBehavior {
+    /// Do nothing.
+    No,
+    /// If there is an inherited reference, match against it and consume it.
+    EatOuter,
+    /// If there is an inherited reference, match against it and consume both references.
+    EatBoth,
+}
+
 /// Choice of typing rules.
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Serialize, Deserialize, Encode, Decode)]
 pub struct RuleOptions {
@@ -55,9 +69,10 @@ pub struct RuleOptions {
     /// What happens with a `&mut?p` pattern matching on `&mut?&mut?T` where the outer reference is
     /// inherited.
     pub inherited_ref_on_ref: InheritedRefOnRefBehavior,
-    /// In the `EatBoth` and `EatInner` cases, if matching against the underlying place fails this
-    /// determines whether we try again in `EatOuter` mode.
-    pub fallback_to_outer: bool,
+    /// In `InheritedRefOnRefBehavior::EatBoth` or `EatInner` modes, if a reference pattern fails
+    /// to match against an underlying place of reference type, and there is an inherited
+    /// reference, this determines if we try matching against it.
+    pub fallback_to_outer: FallbackToOuterBehavior,
     /// Whether a `&p` pattern is allowed on `&mut T`. This is RFC3627 rule 5.
     pub allow_ref_pat_on_ref_mut: bool,
     /// Whether to simplify some expressions, which removes some borrow errors involving mixes of
@@ -249,15 +264,21 @@ pub const TY_BASED_OPTIONS_DOC: &[OptionsDoc] = &[
                 case has a mutability mismatch",
         values: &[
             OptionValue {
-                name: "false",
+                name: "No",
                 doc: "Don't try matching on the outer reference if \
                         matching on the inner reference caused a mutability mismatch",
             },
             OptionValue {
-                name: "true",
+                name: "EatOuter",
                 doc: "Try matching on the outer reference if \
                         matching on the inner reference caused a mutability mismatch",
             },
+            OptionValue {
+                name: "EatBoth",
+                doc: "Try matching on the outer reference if \
+                        matching on the inner reference caused a mutability mismatch. \
+                        If this succeeds, consume both references.",
+            },
         ],
     },
     OptionsDoc {
@@ -370,7 +391,7 @@ impl RuleOptions {
         ref_binding_on_inherited: RefBindingOnInheritedBehavior::ResetBindingMode,
         mut_binding_on_inherited: MutBindingOnInheritedBehavior::ResetBindingMode,
         inherited_ref_on_ref: InheritedRefOnRefBehavior::EatBoth,
-        fallback_to_outer: false,
+        fallback_to_outer: FallbackToOuterBehavior::No,
         allow_ref_pat_on_ref_mut: false,
         simplify_deref_mut: true,
         eat_inherited_ref_alone: false,
@@ -384,7 +405,7 @@ impl RuleOptions {
         ref_binding_on_inherited: RefBindingOnInheritedBehavior::ResetBindingMode,
         mut_binding_on_inherited: MutBindingOnInheritedBehavior::Error,
         inherited_ref_on_ref: InheritedRefOnRefBehavior::EatInner,
-        fallback_to_outer: true,
+        fallback_to_outer: FallbackToOuterBehavior::EatOuter,
         allow_ref_pat_on_ref_mut: true,
         simplify_deref_mut: true,
         eat_inherited_ref_alone: true,
@@ -399,7 +420,7 @@ impl RuleOptions {
         ref_binding_on_inherited: RefBindingOnInheritedBehavior::AllocTemporary,
         mut_binding_on_inherited: MutBindingOnInheritedBehavior::Keep,
         inherited_ref_on_ref: InheritedRefOnRefBehavior::EatOuter,
-        fallback_to_outer: false,
+        fallback_to_outer: FallbackToOuterBehavior::No,
         allow_ref_pat_on_ref_mut: true,
         simplify_deref_mut: true,
         eat_inherited_ref_alone: true,
@@ -434,14 +455,14 @@ impl RuleOptions {
     pub const RFC3627_2021: Self = RuleOptions {
         mut_binding_on_inherited: MutBindingOnInheritedBehavior::ResetBindingMode,
         inherited_ref_on_ref: InheritedRefOnRefBehavior::EatBoth,
-        fallback_to_outer: true,
+        fallback_to_outer: FallbackToOuterBehavior::EatOuter,
         ..RuleOptions::ERGO2024
     };
 
     pub const ERGO2024_BREAKING_ONLY: Self = RuleOptions {
         mut_binding_on_inherited: MutBindingOnInheritedBehavior::Error,
         inherited_ref_on_ref: InheritedRefOnRefBehavior::EatInner,
-        fallback_to_outer: false,
+        fallback_to_outer: FallbackToOuterBehavior::No,
         ..RuleOptions::STABLE_RUST
     };
 

diff --git a/src/solvers/typing_rules.rs b/src/solvers/typing_rules.rs
@@ -30,7 +30,7 @@ pub enum DowngradeMutToRef {
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub struct FallbackToOuter(pub bool);
+pub struct FallbackToOuter(pub FallbackToOuterBehavior);
 
 #[derive(Debug, Clone, Copy)]
 pub enum TypeError {
@@ -134,7 +134,7 @@ impl<'a> TypingPredicate<'a> {
             // Dereference rules
             (P::Ref(p_mtbl, p_inner), T::Ref(mut t_mtbl, _)) => {
                 let mut rule_variant = InheritedRefOnRefBehavior::EatOuter;
-                let mut fallback_to_outer = FallbackToOuter(false);
+                let mut fallback_to_outer = FallbackToOuter(FallbackToOuterBehavior::No);
                 let mut reborrow_after = None;
 
                 // We only inspect the binding mode if there are options that need it.
@@ -167,11 +167,22 @@ impl<'a> TypingPredicate<'a> {
                                         reborrow_after = Some(t_mtbl);
                                         t_mtbl = *inner_mtbl;
                                         underlying_place.deref(a)
-                                    } else if o.fallback_to_outer {
-                                        fallback_to_outer = FallbackToOuter(true);
-                                        self.expr.deref(a)
                                     } else {
-                                        return Err(TypeError::MutabilityMismatch);
+                                        match o.fallback_to_outer {
+                                            FallbackToOuterBehavior::No => {
+                                                return Err(TypeError::MutabilityMismatch)
+                                            }
+                                            FallbackToOuterBehavior::EatOuter => {
+                                                fallback_to_outer =
+                                                    FallbackToOuter(o.fallback_to_outer);
+                                                self.expr.deref(a)
+                                            }
+                                            FallbackToOuterBehavior::EatBoth => {
+                                                fallback_to_outer =
+                                                    FallbackToOuter(o.fallback_to_outer);
+                                                self.expr.deref(a).deref(a)
+                                            }
+                                        }
                                     }
                                 }
                                 InheritedRefOnRefBehavior::EatBoth => {
@@ -186,11 +197,22 @@ impl<'a> TypingPredicate<'a> {
                                     if can_eat_inner {
                                         t_mtbl = *inner_mtbl;
                                         underlying_place.deref(a)
-                                    } else if o.fallback_to_outer {
-                                        fallback_to_outer = FallbackToOuter(true);
-                                        self.expr.deref(a)
                                     } else {
-                                        return Err(TypeError::MutabilityMismatch);
+                                        match o.fallback_to_outer {
+                                            FallbackToOuterBehavior::No => {
+                                                return Err(TypeError::MutabilityMismatch)
+                                            }
+                                            FallbackToOuterBehavior::EatOuter => {
+                                                fallback_to_outer =
+                                                    FallbackToOuter(o.fallback_to_outer);
+                                                self.expr.deref(a)
+                                            }
+                                            FallbackToOuterBehavior::EatBoth => {
+                                                fallback_to_outer =
+                                                    FallbackToOuter(o.fallback_to_outer);
+                                                self.expr.deref(a).deref(a)
+                                            }
+                                        }
                                     }
                                 }
                                 InheritedRefOnRefBehavior::Error => {

diff --git a/tests/snapshots/bundle_rules@min_ergonomics-Expression.snap b/tests/snapshots/bundle_rules@min_ergonomics-Expression.snap
@@ -6,7 +6,7 @@ info:
     match_constructor_through_ref: true
     eat_inherited_ref_alone: false
     inherited_ref_on_ref: Error
-    fallback_to_outer: false
+    fallback_to_outer: "No"
     allow_ref_pat_on_ref_mut: false
     simplify_deref_mut: true
     downgrade_mut_inside_shared: false

diff --git a/tests/snapshots/bundle_rules@min_ergonomics-Sequent.snap b/tests/snapshots/bundle_rules@min_ergonomics-Sequent.snap
@@ -6,7 +6,7 @@ info:
     match_constructor_through_ref: true
     eat_inherited_ref_alone: false
     inherited_ref_on_ref: Error
-    fallback_to_outer: false
+    fallback_to_outer: "No"
     allow_ref_pat_on_ref_mut: false
     simplify_deref_mut: true
     downgrade_mut_inside_shared: false

diff --git a/tests/snapshots/bundle_rules@min_ergonomics-SequentBindingMode.snap b/tests/snapshots/bundle_rules@min_ergonomics-SequentBindingMode.snap
@@ -6,7 +6,7 @@ info:
     match_constructor_through_ref: true
     eat_inherited_ref_alone: false
     inherited_ref_on_ref: Error
-    fallback_to_outer: false
+    fallback_to_outer: "No"
     allow_ref_pat_on_ref_mut: false
     simplify_deref_mut: true
     downgrade_mut_inside_shared: false

diff --git a/tests/snapshots/bundle_rules@nadri-Expression.snap b/tests/snapshots/bundle_rules@nadri-Expression.snap
@@ -6,7 +6,7 @@ info:
     match_constructor_through_ref: true
     eat_inherited_ref_alone: true
     inherited_ref_on_ref: EatOuter
-    fallback_to_outer: false
+    fallback_to_outer: "No"
     allow_ref_pat_on_ref_mut: true
     simplify_deref_mut: true
     downgrade_mut_inside_shared: false

diff --git a/tests/snapshots/bundle_rules@nadri-Sequent.snap b/tests/snapshots/bundle_rules@nadri-Sequent.snap
@@ -6,7 +6,7 @@ info:
     match_constructor_through_ref: true
     eat_inherited_ref_alone: true
     inherited_ref_on_ref: EatOuter
-    fallback_to_outer: false
+    fallback_to_outer: "No"
     allow_ref_pat_on_ref_mut: true
     simplify_deref_mut: true
     downgrade_mut_inside_shared: false

diff --git a/tests/snapshots/bundle_rules@nadri-SequentBindingMode.snap b/tests/snapshots/bundle_rules@nadri-SequentBindingMode.snap
@@ -6,7 +6,7 @@ info:
     match_constructor_through_ref: true
     eat_inherited_ref_alone: true
     inherited_ref_on_ref: EatOuter
-    fallback_to_outer: false
+    fallback_to_outer: "No"
     allow_ref_pat_on_ref_mut: true
     simplify_deref_mut: true
     downgrade_mut_inside_shared: false

diff --git a/tests/snapshots/bundle_rules@rfc3627-Expression.snap b/tests/snapshots/bundle_rules@rfc3627-Expression.snap
@@ -6,7 +6,7 @@ info:
     match_constructor_through_ref: true
     eat_inherited_ref_alone: true
     inherited_ref_on_ref: EatInner
-    fallback_to_outer: true
+    fallback_to_outer: EatOuter
     allow_ref_pat_on_ref_mut: true
     simplify_deref_mut: true
     downgrade_mut_inside_shared: true
@@ -79,7 +79,7 @@ p @ &mut *e: &mut T
 &mut p @ &mut e: &mut &mut T, e mutable
 
 p @ *&mut e: &T
------------------------- "Deref(EatInner, FallbackToOuter)"
+------------------------ "Deref(EatInner, FallbackToOuter(EatOuter))"
 &mut p @ &mut e: &mut &T
 
 p @ &*e: &T

diff --git a/tests/snapshots/bundle_rules@rfc3627-Sequent.snap b/tests/snapshots/bundle_rules@rfc3627-Sequent.snap
@@ -6,7 +6,7 @@ info:
     match_constructor_through_ref: true
     eat_inherited_ref_alone: true
     inherited_ref_on_ref: EatInner
-    fallback_to_outer: true
+    fallback_to_outer: EatOuter
     allow_ref_pat_on_ref_mut: true
     simplify_deref_mut: true
     downgrade_mut_inside_shared: true
@@ -79,7 +79,7 @@ inh, rw ⊢ p: &mut T
 inh, rw ⊢ &mut p: &mut &mut T
 
 real, m ⊢ p: &T
------------------------- "Deref(EatInner, FallbackToOuter)"
+------------------------ "Deref(EatInner, FallbackToOuter(EatOuter))"
 inh, m ⊢ &mut p: &mut &T
 
 inh, ro ⊢ p: &T

diff --git a/tests/snapshots/bundle_rules@rfc3627-SequentBindingMode.snap b/tests/snapshots/bundle_rules@rfc3627-SequentBindingMode.snap
@@ -6,7 +6,7 @@ info:
     match_constructor_through_ref: true
     eat_inherited_ref_alone: true
     inherited_ref_on_ref: EatInner
-    fallback_to_outer: true
+    fallback_to_outer: EatOuter
     allow_ref_pat_on_ref_mut: true
     simplify_deref_mut: true
     downgrade_mut_inside_shared: true
@@ -111,7 +111,7 @@ ref mut, rw ⊢ p: T
 ref mut, rw ⊢ &mut p: &mut T
 
 move, m ⊢ p: &T
------------------------ "Deref(EatInner, FallbackToOuter)"
+----------------------- "Deref(EatInner, FallbackToOuter(EatOuter))"
 ref mut, m ⊢ &mut p: &T
 
 ref, ro ⊢ p: T

diff --git a/tests/snapshots/bundle_rules@rfc3627_2021-Expression.snap b/tests/snapshots/bundle_rules@rfc3627_2021-Expression.snap
@@ -6,7 +6,7 @@ info:
     match_constructor_through_ref: true
     eat_inherited_ref_alone: true
     inherited_ref_on_ref: EatBoth
-    fallback_to_outer: true
+    fallback_to_outer: EatOuter
     allow_ref_pat_on_ref_mut: true
     simplify_deref_mut: true
     downgrade_mut_inside_shared: true
@@ -83,7 +83,7 @@ p @ *e: T
 &mut p @ &mut e: &mut &mut T
 
 p @ *&mut e: &T
------------------------- "Deref(EatBoth, FallbackToOuter)"
+------------------------ "Deref(EatBoth, FallbackToOuter(EatOuter))"
 &mut p @ &mut e: &mut &T
 
 p @ *&*e: T

diff --git a/tests/snapshots/bundle_rules@rfc3627_2021-Sequent.snap b/tests/snapshots/bundle_rules@rfc3627_2021-Sequent.snap
@@ -6,7 +6,7 @@ info:
     match_constructor_through_ref: true
     eat_inherited_ref_alone: true
     inherited_ref_on_ref: EatBoth
-    fallback_to_outer: true
+    fallback_to_outer: EatOuter
     allow_ref_pat_on_ref_mut: true
     simplify_deref_mut: true
     downgrade_mut_inside_shared: true
@@ -83,7 +83,7 @@ real, m ⊢ p: T
 inh, m ⊢ &mut p: &mut &mut T
 
 real, m ⊢ p: &T
------------------------- "Deref(EatBoth, FallbackToOuter)"
+------------------------ "Deref(EatBoth, FallbackToOuter(EatOuter))"
 inh, m ⊢ &mut p: &mut &T
 
 real, ro ⊢ p: T

diff --git a/tests/snapshots/bundle_rules@rfc3627_2021-SequentBindingMode.snap b/tests/snapshots/bundle_rules@rfc3627_2021-SequentBindingMode.snap
@@ -6,7 +6,7 @@ info:
     match_constructor_through_ref: true
     eat_inherited_ref_alone: true
     inherited_ref_on_ref: EatBoth
-    fallback_to_outer: true
+    fallback_to_outer: EatOuter
     allow_ref_pat_on_ref_mut: true
     simplify_deref_mut: true
     downgrade_mut_inside_shared: true
@@ -115,7 +115,7 @@ move, m ⊢ p: T
 ref mut, m ⊢ &mut p: &mut T
 
 move, m ⊢ p: &T
------------------------ "Deref(EatBoth, FallbackToOuter)"
+----------------------- "Deref(EatBoth, FallbackToOuter(EatOuter))"
 ref mut, m ⊢ &mut p: &T
 
 move, ro ⊢ p: T

diff --git a/tests/snapshots/bundle_rules@rfc3627_2024_min-Expression.snap b/tests/snapshots/bundle_rules@rfc3627_2024_min-Expression.snap
@@ -6,7 +6,7 @@ info:
     match_constructor_through_ref: true
     eat_inherited_ref_alone: false
     inherited_ref_on_ref: EatInner
-    fallback_to_outer: false
+    fallback_to_outer: "No"
     allow_ref_pat_on_ref_mut: false
     simplify_deref_mut: true
     downgrade_mut_inside_shared: false

diff --git a/tests/snapshots/bundle_rules@rfc3627_2024_min-Sequent.snap b/tests/snapshots/bundle_rules@rfc3627_2024_min-Sequent.snap
@@ -6,7 +6,7 @@ info:
     match_constructor_through_ref: true
     eat_inherited_ref_alone: false
     inherited_ref_on_ref: EatInner
-    fallback_to_outer: false
+    fallback_to_outer: "No"
     allow_ref_pat_on_ref_mut: false
     simplify_deref_mut: true
     downgrade_mut_inside_shared: false

diff --git a/tests/snapshots/bundle_rules@rfc3627_2024_min-SequentBindingMode.snap b/tests/snapshots/bundle_rules@rfc3627_2024_min-SequentBindingMode.snap
@@ -6,7 +6,7 @@ info:
     match_constructor_through_ref: true
     eat_inherited_ref_alone: false
     inherited_ref_on_ref: EatInner
-    fallback_to_outer: false
+    fallback_to_outer: "No"
     allow_ref_pat_on_ref_mut: false
     simplify_deref_mut: true
     downgrade_mut_inside_shared: false

diff --git a/tests/snapshots/bundle_rules@stable_rust-Expression.snap b/tests/snapshots/bundle_rules@stable_rust-Expression.snap
@@ -6,7 +6,7 @@ info:
     match_constructor_through_ref: true
     eat_inherited_ref_alone: false
     inherited_ref_on_ref: EatBoth
-    fallback_to_outer: false
+    fallback_to_outer: "No"
     allow_ref_pat_on_ref_mut: false
     simplify_deref_mut: true
     downgrade_mut_inside_shared: false

diff --git a/tests/snapshots/bundle_rules@stable_rust-Sequent.snap b/tests/snapshots/bundle_rules@stable_rust-Sequent.snap
@@ -6,7 +6,7 @@ info:
     match_constructor_through_ref: true
     eat_inherited_ref_alone: false
     inherited_ref_on_ref: EatBoth
-    fallback_to_outer: false
+    fallback_to_outer: "No"
     allow_ref_pat_on_ref_mut: false
     simplify_deref_mut: true
     downgrade_mut_inside_shared: false