Address naming and review comments

Author: Kristoffer Ström

clarity/src/vm/analysis/type_checker/contexts.rs

@@ -87,14 +87,9 @@ impl TypeMap {
     }
 
     /// Like set_type but forcing a change if already set
-    pub fn override_type(&mut self, expr: &SymbolicExpression, type_sig: TypeSignature) {
-        match self.map {
-            TypeMapDataType::Map(ref mut map) => {
-                map.insert(expr.id, type_sig);
-            }
-            TypeMapDataType::Set(ref mut map) => {
-                map.insert(expr.id);
-            }
+    pub fn overwrite_type(&mut self, expr: &SymbolicExpression, type_sig: TypeSignature) {
+        if let TypeMapDataType::Map(ref mut map) = self.map {
+            map.insert(expr.id, type_sig);
         }
     }