+## note on recursive closures
+
+The following example shows a recursive lambda, that results in a
+closure that captures itself.
+```
+(let ([f (closure lambda0 (f))])
+ (f 42))
+```
+When this happens, `codegen-let` will insert `(f . 'self-captive)`
+into the environment when codegen'ing the closure. `codegen-closure`
+will then pick this up, and use it to insert its own heap address into
+its inner environment.
+