Extend clauses.rs to support impl/dyn Trait

Author: KiChjang

chalk-solve/src/clauses.rs

@@ -167,6 +167,23 @@ fn program_clauses_that_could_match(
                 }
             }
 
+            // Check for impl and dyn Traits so that we generate
+            // `Implemented(impl Foo + Bar) :- Implemented(Foo), Implemented(Bar)`
+            match trait_ref.self_type_parameter() {
+                Some(Ty::Opaque(qwc)) | Some(Ty::Dyn(qwc)) => {
+                    clauses.push(ProgramClauseImplication {
+                        consequence: trait_ref.clone().cast(),
+                        conditions: qwc
+                            .value
+                            .iter()
+                            .cloned()
+                            .casted()
+                            .collect(),
+                    }.cast());
+                }
+                _ => {}
+            }
+
             // TODO sized, unsize_trait, builtin impls?
         }
         DomainGoal::Holds(WhereClause::ProjectionEq(projection_predicate)) => {