diff --git a/lalrpop/src/grammar/free_variables.rs b/lalrpop/src/grammar/free_variables.rs
index f6b18ed..aaa5cd4 100644
--- a/lalrpop/src/grammar/free_variables.rs
+++ b/lalrpop/src/grammar/free_variables.rs
@@ -1,5 +1,6 @@
 use grammar::parse_tree::{self, TypeParameter};
 use grammar::repr;
+use std::iter;
 
 /// Finds the set of "free variables" in something -- that is, the
 /// type/lifetime parameters that appear and are not bound. For
@@ -19,9 +20,7 @@ impl<T: FreeVariables> FreeVariables for Option<T> {
 
 impl<T: FreeVariables> FreeVariables for Vec<T> {
     fn free_variables(&self) -> Vec<TypeParameter> {
-        self.into_iter()
-            .flat_map(|e| e.free_variables())
-            .collect()
+        self.into_iter().flat_map(|e| e.free_variables()).collect()
     }
 }
 
@@ -31,7 +30,8 @@ impl FreeVariables for repr::TypeRepr {
             repr::TypeRepr::Tuple(tys) => tys.free_variables(),
             repr::TypeRepr::Nominal(data) => data.free_variables(),
             repr::TypeRepr::Associated {
-                type_parameter, id: _
+                type_parameter,
+                id: _,
             } => vec![TypeParameter::Id(type_parameter.clone())],
             repr::TypeRepr::Lifetime(l) => vec![TypeParameter::Lifetime(l.clone())],
             repr::TypeRepr::Ref {
@@ -69,3 +69,61 @@ impl FreeVariables for repr::NominalTypeRepr {
             .collect()
     }
 }
+
+impl<T: FreeVariables> FreeVariables for parse_tree::WhereClause<T> {
+    fn free_variables(&self) -> Vec<TypeParameter> {
+        match self {
+            parse_tree::WhereClause::Lifetime { lifetime, bounds } =>
+                iter::once(TypeParameter::Lifetime(lifetime.clone()))
+                    .chain(bounds.iter().map(|l| TypeParameter::Lifetime(l.clone())))
+                    .collect(),
+
+            parse_tree::WhereClause::Type { forall, ty, bounds } => ty
+                .free_variables()
+                .into_iter()
+                .chain(bounds.free_variables())
+                .filter(|tp| !forall.contains(tp))
+                .collect(),
+        }
+    }
+}
+
+impl<T: FreeVariables> FreeVariables for parse_tree::TypeBoundParameter<T> {
+    fn free_variables(&self) -> Vec<TypeParameter> {
+        match self {
+            parse_tree::TypeBoundParameter::Lifetime(l) => vec![TypeParameter::Lifetime(l.clone())],
+            parse_tree::TypeBoundParameter::TypeParameter(t) => t.free_variables(),
+            parse_tree::TypeBoundParameter::Associated(..) => vec![],
+        }
+    }
+}
+
+impl<T: FreeVariables> FreeVariables for parse_tree::TypeBound<T> {
+    fn free_variables(&self) -> Vec<TypeParameter> {
+        match self {
+            parse_tree::TypeBound::Lifetime(l) => vec![TypeParameter::Lifetime(l.clone())],
+            parse_tree::TypeBound::Fn {
+                forall,
+                path,
+                parameters,
+                ret,
+            } => path
+                .free_variables()
+                .into_iter()
+                .chain(parameters.free_variables())
+                .chain(ret.free_variables())
+                .filter(|tp| !forall.contains(tp))
+                .collect(),
+            parse_tree::TypeBound::Trait {
+                forall,
+                path,
+                parameters,
+            } => path
+                .free_variables()
+                .into_iter()
+                .chain(parameters.free_variables())
+                .filter(|tp| !forall.contains(tp))
+                .collect(),
+        }
+    }
+}
diff --git a/lalrpop/src/lr1/codegen/ascent.rs b/lalrpop/src/lr1/codegen/ascent.rs
index 248d86b..cb5f876 100644
--- a/lalrpop/src/lr1/codegen/ascent.rs
+++ b/lalrpop/src/lr1/codegen/ascent.rs
@@ -145,17 +145,16 @@ impl<'ascent, 'grammar, W: Write>
             .cloned()
             .collect();
 
-        let mut referenced_where_clauses = Set::new();
-        for wc in &grammar.where_clauses {
-            wc.map(|ty| {
-                if ty.free_variables()
+        let referenced_where_clauses: Set<_> = grammar
+            .where_clauses
+            .iter()
+            .filter(|wc| {
+                wc.free_variables()
                     .iter()
                     .any(|p| nonterminal_type_params.contains(p))
-                {
-                    referenced_where_clauses.insert(wc.clone());
-                }
-            });
-        }
+            })
+            .cloned()
+            .collect();
 
         let nonterminal_where_clauses: Vec<_> = grammar
             .where_clauses
@@ -547,7 +546,7 @@ impl<'ascent, 'grammar, W: Write>
             vec![format!(
                 "{}TOKENS: Iterator<Item=Result<{},{}>>",
                 self.prefix, triple_type, iter_error_type
-            ),],
+            )],
             None,
             true, // include grammar parameters
             fn_args,
diff --git a/lalrpop/src/lr1/codegen/parse_table.rs b/lalrpop/src/lr1/codegen/parse_table.rs
index adb36d0..9e1fc48 100644
--- a/lalrpop/src/lr1/codegen/parse_table.rs
+++ b/lalrpop/src/lr1/codegen/parse_table.rs
@@ -319,17 +319,16 @@ impl<'ascent, 'grammar, W: Write> CodeGenerator<'ascent, 'grammar, W, TableDrive
             .cloned()
             .collect();
 
-        let mut referenced_where_clauses = Set::new();
-        for wc in &grammar.where_clauses {
-            wc.map(|ty| {
-                if ty.free_variables()
+        let referenced_where_clauses: Set<_> = grammar
+            .where_clauses
+            .iter()
+            .filter(|wc| {
+                wc.free_variables()
                     .iter()
                     .any(|p| symbol_type_params.contains(p))
-                {
-                    referenced_where_clauses.insert(wc.clone());
-                }
-            });
-        }
+            })
+            .cloned()
+            .collect();
 
         let symbol_where_clauses: Vec<_> = grammar
             .where_clauses