Get rid of eval

src/Memoize.jl

@@ -4,6 +4,13 @@ export @memoize, memoize_cache
 
 cache_name(f) = Symbol("##", f, "_memoized_cache")
 
+function try_empty_cache(f)
+    try
+        empty!(memoize_cache(f))
+    catch
+    end
+end
+
 macro memoize(args...)
     if length(args) == 1
         dicttype = :(IdDict)
@@ -51,11 +58,8 @@ macro memoize(args...)
         end
     end
 
-    fcachename = cache_name(f)
+    @gensym fcache
     mod = __module__
-    fcache = isdefined(mod, fcachename) ?
-             getfield(mod, fcachename) :
-             Core.eval(mod, :(const $fcachename = $cache_dict))
 
     body = quote
         get!($fcache, ($(tup...),)) do
@@ -72,17 +76,21 @@ macro memoize(args...)
     end
 
     esc(quote
+        $Memoize.try_empty_cache($f) # So that redefining a function doesn't leak memory through
+                                     # the previous cache.
+        # The `local` qualifier will make this performant even in the global scope.
+        local $fcache = $cache_dict
+        $(cache_name(f)) = $fcache   # for `memoize_cache(f)`
         $(combinedef(def_dict_unmemoized))
-        empty!($fcache)
         Base.@__doc__ $(combinedef(def_dict))
     end)
 
 end
 
 function memoize_cache(f::Function)
-    # This will fail in certain circumstances (eg. @memoize Base.sin(::MyNumberType) = ...) but I don't think there's 
-    # a clean answer here, because we can already have multiple caches for certain functions, if the methods are 
-    # defined in different modules.
+    # This will fail in certain circumstances (eg. @memoize Base.sin(::MyNumberType) = ...) but I
+    # don't think there's a clean answer here, because we can already have multiple caches for
+    # certain functions, if the methods are defined in different modules.
     getproperty(parentmodule(f), cache_name(f))
 end
 

test/runtests.jl

@@ -352,3 +352,5 @@ end
 @test dict_call("bb") == 2
 @test run == 2
 
+@memoize non_allocating(x) = x+1
+@test @allocated(non_allocating(10)) == 0