Mutable references should not be Copy/Clone

book/src/clauses/well_known_traits.md

@@ -36,7 +36,8 @@ Some common examples of auto traits are `Send` and `Sync`.
 | trait objects   | ⚬    | ⚬    | ⚬     |  ✅    | ⚬    | ⚬   | ⚬      |  ⚬       |    ⚬        |
 | functions ptrs  | ✅    | ✅    | ✅     | ⚬     | ⚬    | ❌   | ⚬      |  ⚬       |    ❌         |
 | raw ptrs        | ✅   |  ✅  |   ✅   |  ⚬    |   ⚬   |  ⚬  |   ⚬    |   ⚬      |      ❌      |
-| references      | ✅   |  ✅  |   ✅   |  ⚬    |   ⚬   |  ⚬  |   ⚬    |   ⚬      |      ❌      |
+| immutable refs  | ✅   |  ✅  |   ✅   |  ⚬    |   ⚬   |  ⚬  |   ⚬    |   ⚬      |      ❌      |
+| mutable refs    | ⚬    |  ⚬   |   ✅   |  ⚬    |   ⚬   |  ⚬  |   ⚬    |   ⚬      |      ❌      |
 | slices          | ⚬     | ⚬    | ⚬     |   ✅    | ⚬   | ⚬   | ⚬      |  ⚬       |    ❌       |
 | arrays❌         | ❌     | ❌    | ❌     | ❌      | ⚬   | ⚬   | ⚬      |  ⚬       |    ❌        |
 | closures❌       | ❌     | ❌    | ❌     | ⚬      | ⚬   | ❌   | ⚬      |  ⚬       |    ❌        |

chalk-solve/src/clauses/builtin_traits/copy.rs

@@ -1,7 +1,7 @@
 use crate::clauses::builtin_traits::needs_impl_for_tys;
 use crate::clauses::ClauseBuilder;
 use crate::{Interner, RustIrDatabase, TraitRef};
-use chalk_ir::{ApplicationTy, Substitution, TyData, TypeName};
+use chalk_ir::{ApplicationTy, Mutability, Substitution, TyData, TypeName};
 
 fn push_tuple_copy_conditions<I: Interner>(
     db: &dyn RustIrDatabase<I>,
@@ -41,7 +41,9 @@ pub fn add_copy_program_clauses<I: Interner>(
             TypeName::Tuple(arity) => {
                 push_tuple_copy_conditions(db, builder, trait_ref, *arity, substitution)
             }
-            TypeName::Raw(_) | TypeName::Ref(_) => builder.push_fact(trait_ref.clone()),
+            TypeName::Raw(_) | TypeName::Ref(Mutability::Not) => {
+                builder.push_fact(trait_ref.clone())
+            }
             _ => return,
         },
         TyData::Function(_) => builder.push_fact(trait_ref.clone()),

tests/lowering/mod.rs

@@ -555,7 +555,7 @@ fn slices() {
         }
 
         error_msg {
-            "parse error: UnrecognizedToken { token: (29, Token(30, \"]\"), 30), expected: [\"\\\"&\\\"\", \"\\\"(\\\"\", \"\\\"*\\\"\", \"\\\"<\\\"\", \"\\\"[\\\"\", \"\\\"bool\\\"\", \"\\\"char\\\"\", \"\\\"dyn\\\"\", \"\\\"f32\\\"\", \"\\\"f64\\\"\", \"\\\"fn\\\"\", \"\\\"for\\\"\", \"\\\"i128\\\"\", \"\\\"i16\\\"\", \"\\\"i32\\\"\", \"\\\"i64\\\"\", \"\\\"i8\\\"\", \"\\\"isize\\\"\", \"\\\"u128\\\"\", \"\\\"u16\\\"\", \"\\\"u32\\\"\", \"\\\"u64\\\"\", \"\\\"u8\\\"\", \"\\\"usize\\\"\", \"r#\\\"([A-Za-z]|_)([A-Za-z0-9]|_)*\\\"#\"] }"
+            "parse error: UnrecognizedToken { token: (29, Token(31, \"]\"), 30), expected: [\"\\\"&\\\"\", \"\\\"(\\\"\", \"\\\"*\\\"\", \"\\\"<\\\"\", \"\\\"[\\\"\", \"\\\"bool\\\"\", \"\\\"char\\\"\", \"\\\"dyn\\\"\", \"\\\"f32\\\"\", \"\\\"f64\\\"\", \"\\\"fn\\\"\", \"\\\"for\\\"\", \"\\\"i128\\\"\", \"\\\"i16\\\"\", \"\\\"i32\\\"\", \"\\\"i64\\\"\", \"\\\"i8\\\"\", \"\\\"isize\\\"\", \"\\\"u128\\\"\", \"\\\"u16\\\"\", \"\\\"u32\\\"\", \"\\\"u64\\\"\", \"\\\"u8\\\"\", \"\\\"usize\\\"\", \"r#\\\"([A-Za-z]|_)([A-Za-z0-9]|_)*\\\"#\"] }"
         }
     }
 }

tests/test/refs.rs

@@ -1,7 +1,7 @@
 use super::*;
 
 #[test]
-fn refs_are_well_formed() {
+fn immut_refs_are_well_formed() {
     test! {
         program { }
 
@@ -14,7 +14,7 @@ fn refs_are_well_formed() {
 }
 
 #[test]
-fn refs_are_sized() {
+fn immut_refs_are_sized() {
     test! {
         program {
             #[lang(sized)]
@@ -30,7 +30,36 @@ fn refs_are_sized() {
 }
 
 #[test]
-fn refs_are_copy() {
+fn mut_refs_are_well_formed() {
+    test! {
+        program { }
+
+        goal {
+            forall<'a, T> { WellFormed(&'a mut T) }
+        } yields {
+            "Unique; substitution [], lifetime constraints []"
+        }
+    }
+}
+
+#[test]
+fn mut_refs_are_sized() {
+    test! {
+        program {
+            #[lang(sized)]
+            trait Sized { }
+        }
+
+        goal {
+            forall<'a, T> { &'a mut T: Sized }
+        } yields {
+            "Unique; substitution [], lifetime constraints []"
+        }
+    }
+}
+
+#[test]
+fn immut_refs_are_copy() {
     test! {
         program {
             #[lang(copy)]
@@ -46,7 +75,7 @@ fn refs_are_copy() {
 }
 
 #[test]
-fn refs_are_clone() {
+fn immut_refs_are_clone() {
     test! {
         program {
             #[lang(clone)]
@@ -60,3 +89,35 @@ fn refs_are_clone() {
         }
     }
 }
+
+#[test]
+fn mut_refs_are_not_copy() {
+    test! {
+        program {
+            #[lang(copy)]
+            trait Copy { }
+        }
+
+        goal {
+            forall<'a, T> { not { &'a mut T: Copy } }
+        } yields {
+            "Unique; substitution [], lifetime constraints []"
+        }
+    }
+}
+
+#[test]
+fn mut_refs_are_not_clone() {
+    test! {
+        program {
+            #[lang(clone)]
+            trait Clone { }
+        }
+
+        goal {
+            forall<'a, T> { not { &'a mut T: Clone } }
+        } yields {
+            "Unique; substitution [], lifetime constraints []"
+        }
+    }
+}