--- a/src/func.h	Thu Sep 12 08:25:03 2019 +0200
+++ b/src/func.h	Thu Sep 12 08:25:27 2019 +0200
@@ -39,7 +39,7 @@
     /// Vector of yarg_desc_t values, each describing an argument, in order of
     /// appearance.
     yvec_t args;
-    /// Vector of yarg_desc_t values, each describing a value to be captured in
+    /// Vector of yref_t values, each describing a value to be captured in
     /// a closure. When defining the function, the interpreter should copy the
     /// values of these references into the closure yexpr_t value (via the
     /// to-be-implemented _mkclsr built-in). / When calling a function, the

--- a/src/sizes_test.c	Thu Sep 12 08:25:03 2019 +0200
+++ b/src/sizes_test.c	Thu Sep 12 08:25:27 2019 +0200
@@ -17,6 +17,7 @@
     PRINT_SIZE(ystr_t);
     PRINT_SIZE(yvalue_id_t);
     PRINT_SIZE(yvec_t);
+    PRINT_SIZE(yclosure_t);
 
     PRINT_SIZE(YREF_TYPE);
     PRINT_SIZE(YEXPR_TYPE);
@@ -28,6 +29,12 @@
 void assert_sizes(void) {
     assert(16 == sizeof(ystr_t));
     assert(16 == sizeof(yvec_t));
+
+    assert(8 == sizeof(yatom_t));
+    assert(24 == sizeof(yexpr_t));
+    assert(16 == sizeof(yref_t));
+    assert(64 == sizeof(yfunc_t));
+    assert(32 == sizeof(yclosure_t));
 }
 
 /**

--- a/src/types.h	Thu Sep 12 08:25:03 2019 +0200
+++ b/src/types.h	Thu Sep 12 08:25:27 2019 +0200
@@ -115,10 +115,10 @@
     /// closure data.
     YEXPR_FUNC = 6,
     /// A reference to a built-in function.
-    YEXPR_BUILTIN = 6,
+    YEXPR_BUILTIN = 7,
     /// An exception described by the `str` field - when returned from a
     /// function, the interpreter "bubbles up" the call stack.
-    YEXPR_EXCEPTION = 7,
+    YEXPR_EXCEPTION = 8,
 } YEXPR_TYPE;
 
 /**
@@ -141,7 +141,7 @@
         /// A builtin such as `for`, `let`, ...
         YBUILTIN_TYPE builtin;
         /// A closure, i.e. function reference with associated data.
-        yclosure_t closure;
+        yclosure_t* closure;
     } value;
     /// Type of this expression.
     YEXPR_TYPE typ;