Change a test and some other minor things

Author: scalexm

src/ir/mod.rs

@@ -2,7 +2,7 @@ use cast::Cast;
 use chalk_parse::ast;
 use lalrpop_intern::InternedString;
 use solve::infer::{TyInferenceVariable, LifetimeInferenceVariable};
-use std::collections::{HashMap, BTreeMap};
+use std::collections::{HashSet, HashMap, BTreeMap};
 use std::sync::Arc;
 
 pub type Identifier = InternedString;
@@ -87,8 +87,6 @@ impl Environment {
     pub fn add_clauses<I>(&self, clauses: I) -> Arc<Environment>
         where I: IntoIterator<Item = DomainGoal>
     {
-        use std::collections::HashSet;
-
         let mut env = self.clone();
         let env_clauses: HashSet<_> = env.clauses.into_iter().chain(clauses).collect();
         env.clauses = env_clauses.into_iter().collect();

src/lower/default.rs

@@ -18,7 +18,7 @@ impl Program {
 
                 // If a positive or negative impl is already provided for a type family
                 // which includes `MyStruct`, we do not generate a default impl.
-                if self.provide_impl_for(trait_ref.clone(), struct_datum) {
+                if self.impl_provided_for(trait_ref.clone(), struct_datum) {
                     continue;
                 }
 
@@ -35,7 +35,7 @@ impl Program {
         }
     }
 
-    fn provide_impl_for(&self, trait_ref: TraitRef, struct_datum: &StructDatum) -> bool {
+    fn impl_provided_for(&self, trait_ref: TraitRef, struct_datum: &StructDatum) -> bool {
         let goal: DomainGoal = trait_ref.cast();
 
         let env = Environment::new();

src/solve/test.rs

@@ -1431,7 +1431,12 @@ fn auto_trait_without_impls() {
             #[auto] trait Send { }
 
             struct i32 { }
-            struct Vec<T> { }
+
+            struct Useless<T> { }
+
+            struct Data<T> {
+                data: T
+            }
         }
 
         goal {
@@ -1440,9 +1445,20 @@ fn auto_trait_without_impls() {
             "Unique"
         }
 
+        // No fields so `Useless<T>` is `Send`.
         goal {
             forall<T> {
-                Vec<T>: Send
+                Useless<T>: Send
+            }
+        } yields {
+            "Unique"
+        }
+
+        goal {
+            forall<T> {
+                if (T: Send) {
+                    Data<T>: Send
+                }
             }
         } yields {
             "Unique"
@@ -1523,6 +1539,13 @@ fn coinductive_semantics() {
             "CannotProve"
         }
 
+        // `WellFormed(T)` is needed here because of the expanded bound `WellFormed(Ptr<List<T>>: Send)`
+        // on the default `List<T>: Send` impl, which will need that `List<T>` is well-formed in order to be
+        // proven, which will in turn need that `T` is well-formed.
+        //
+        // In fact, as soon as there is a field which is referencing `T` with an indirection like `Foo<Bar<T>>`,
+        // we need to add the `WellFormed(T)` because the `if (T: Send)` elaborates `WellFormed(T: Send)` but not
+        // `WellFormed(T)`. This is not an issue, but is maybe a bit inconsistent.
         goal {
             forall<T> {
                 if (WellFormed(T), T: Send) {