Mutated Immutable

This checks for globals, WasmGC struct fields and arrays that are not declared mutable, but are mutated unexpectedly.

Specifically:

• global.set will mutate a global
• struct.set will mutate a WasmGC struct field
• array.set, array.fill, array.init_data and array.init_elem will mutate a WasmGC array

Global types and field types aren't defined with a mut keyword are immutable. It's invalid to mutate them.

Globals

(module
  (global i32
    i32.const 0)
  (func
    (global.set 0
      (i32.const 0))))

Struct Fields

(module
  (type (struct (field i32)))
  (func (param (ref 0))
    local.get 0
    i32.const 0
    struct.set 0 0))

Arrays

(module
  (type (array i32))
  (func (param (ref 0))
    local.get 0
    i32.const 0
    i32.const 0
    array.set 0))