Merge pull request #416 from dtolnay/filter

Remove filter no longer necessary for rustc >=1.7

serde_codegen/src/bound.rs

@@ -1,5 +1,3 @@
-use std::collections::HashSet;
-
 use aster::AstBuilder;
 
 use syntax::ast;
@@ -63,8 +61,6 @@ pub fn with_bound<F>(
             item.body.all_fields()
                 .filter(|&field| filter(&field.attrs))
                 .map(|field| &field.ty)
-                // TODO this filter can be removed later, see comment on function
-                .filter(|ty| contains_generic(ty, generics))
                 .filter(|ty| !contains_recursion(ty, item.ident))
                 .map(|ty| strip_reference(ty))
                 .map(|ty| builder.where_predicate()
@@ -76,44 +72,6 @@ pub fn with_bound<F>(
         .build()
 }
 
-// Rust <1.7 enforces that `where` clauses involve generic type parameters. The
-// corresponding compiler error is E0193. It is no longer enforced in Rust >=1.7
-// so this filtering can be removed in the future when we stop supporting <1.7.
-//
-// E0193 means we must not generate a `where` clause like `i32: Serialize`
-// because even though i32 implements Serialize, i32 is not a generic type
-// parameter. Clauses like `T: Serialize` and `Option<T>: Serialize` are okay.
-// This function decides whether a given type references any of the generic type
-// parameters in the input `Generics`.
-fn contains_generic(ty: &ast::Ty, generics: &ast::Generics) -> bool {
-    struct FindGeneric<'a> {
-        generic_names: &'a HashSet<ast::Name>,
-        found_generic: bool,
-    }
-    impl<'a, 'v> visit::Visitor<'v> for FindGeneric<'a> {
-        fn visit_path(&mut self, path: &'v ast::Path, _id: ast::NodeId) {
-            if !path.global
-                    && path.segments.len() == 1
-                    && self.generic_names.contains(&path.segments[0].identifier.name) {
-                self.found_generic = true;
-            } else {
-                visit::walk_path(self, path);
-            }
-        }
-    }
-
-    let generic_names: HashSet<_> = generics.ty_params.iter()
-        .map(|ty_param| ty_param.ident.name)
-        .collect();
-
-    let mut visitor = FindGeneric {
-        generic_names: &generic_names,
-        found_generic: false,
-    };
-    visit::walk_ty(&mut visitor, ty);
-    visitor.found_generic
-}
-
 // We do not attempt to generate any bounds based on field types that are
 // directly recursive, as in:
 //