Document the fact that in IR codegen only explicitly referenced functions are added to internal dispatch

Author: cameel

docs/ir-breaking-changes.rst

@@ -278,6 +278,12 @@ The ID ``0`` is reserved for uninitialized function pointers which then cause a
 In the old code generator, internal function pointers are initialized with a special function that always causes a panic.
 This causes a storage write at construction time for internal function pointers in storage.
 
+.. note::
+    The compiler is free to omit internal functions that are never explicitly referenced by name.
+    As a consequence, assigning to a function type variable in inline assembly does not guarantee
+    that the assigned value will be included in the internal dispatch.
+    The function must also be explicitly referenced elsewhere in the code.
+
 Cleanup
 -------
 

docs/types/value-types.rst

@@ -894,6 +894,13 @@ the contract code is never going to be updated.
 It is also always possible to side-step any safeguards by using inline assembly.
 Such use always needs careful consideration.
 
+.. note::
+    The removal of unused internal functions only takes into account explicit references to
+    such functions by name.
+    Implicit references, such as assigning a new value to a function type variable in inline assembly
+    may still lead to the removal of the function if it is not also referenced explicitly elsewhere
+    in the source.
+
 Examples
 ^^^^^^^^