Relate with contravariant and covariant

Author: jackh726

chalk-solve/src/infer/unify.rs

@@ -393,13 +393,13 @@ impl<'t, I: Interner> Unifier<'t, I> {
         if let Variance::Invariant | Variance::Contravariant = variance {
             let a_universal = self.table.instantiate_binders_universally(interner, a);
             let b_existential = self.table.instantiate_binders_existentially(interner, b);
-            Zip::zip_with(self, variance, &a_universal, &b_existential)?;
+            Zip::zip_with(self, Variance::Contravariant, &a_universal, &b_existential)?;
         }
 
         if let Variance::Invariant | Variance::Covariant = variance {
             let b_universal = self.table.instantiate_binders_universally(interner, b);
             let a_existential = self.table.instantiate_binders_existentially(interner, a);
-            Zip::zip_with(self, variance, &a_existential, &b_universal)?;
+            Zip::zip_with(self, Variance::Covariant, &a_existential, &b_universal)?;
         }
 
         Ok(())

tests/test/existential_types.rs

@@ -337,10 +337,9 @@ fn dyn_binders_reverse() {
             }
         } yields {
             "Unique; substitution [], lifetime constraints [\
-            InEnvironment { environment: Env([]), goal: '!10_0: '!10_1 }, \
-            InEnvironment { environment: Env([]), goal: '!10_1: '!10_0 }, \
-            InEnvironment { environment: Env([]), goal: '!13_0: '!13_1 }, \
-            InEnvironment { environment: Env([]), goal: '!13_1: '!13_0 }]"
+                InEnvironment { environment: Env([]), goal: '!9_0: '!9_1 }, \
+                InEnvironment { environment: Env([]), goal: '!9_1: '!9_0 }\
+            ]"
         }
 
         // Note: these constraints are ultimately unresolveable (we
@@ -353,10 +352,8 @@ fn dyn_binders_reverse() {
             }
         } yields {
             "Unique; substitution [], lifetime constraints [\
-            InEnvironment { environment: Env([]), goal: '!12_0: '!12_1 }, \
-            InEnvironment { environment: Env([]), goal: '!12_1: '!12_0 }, \
-            InEnvironment { environment: Env([]), goal: '!9_0: '!9_1 }, \
-            InEnvironment { environment: Env([]), goal: '!9_1: '!9_0 }\
+                InEnvironment { environment: Env([]), goal: '!7_0: '!7_1 }, \
+                InEnvironment { environment: Env([]), goal: '!7_1: '!7_0 }\
             ]"
         }
 

tests/test/subtype.rs

@@ -79,11 +79,20 @@ fn fn_lifetime_variance_args() {
 
         goal {
             for<'a, 'b> fn(&'a u32, &'b u32) = for<'a> fn(&'a u32, &'a u32)
-        } yields {
-            "Unique;substitution [], lifetime constraints [\
-                InEnvironment { environment: Env([]), goal: '!1_0: '!1_1 }, \
-                InEnvironment { environment: Env([]), goal: '!1_1: '!1_0 }  \
-            ]"
+        } yields[SolverChoice::recursive()] {
+            "Unique; for<?U1,?U2,?U2> { substitution [], lifetime constraints [\
+                InEnvironment { environment: Env([]), goal: '!1_0: '^0.0 }, \
+                InEnvironment { environment: Env([]), goal: '!1_1: '^0.0 }, \
+                InEnvironment { environment: Env([]), goal: '!2_0: '^0.1 }, \
+                InEnvironment { environment: Env([]), goal: '!2_0: '^0.2 }\
+            ] }"
+        } yields[SolverChoice::slg_default()] {
+            "Unique; for<?U2,?U2,?U1> { substitution [], lifetime constraints [\
+                InEnvironment { environment: Env([]), goal: '!1_0: '^0.2 }, \
+                InEnvironment { environment: Env([]), goal: '!1_1: '^0.2 }, \
+                InEnvironment { environment: Env([]), goal: '!2_0: '^0.0 }, \
+                InEnvironment { environment: Env([]), goal: '!2_0: '^0.1 }\
+            ] }"
         }
     }
 }