[Issue 14125] @trusted nested helper functions in std.file

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=14125

--- Comment #37 from Walter Bright <bugzilla at digitalmars.com> ---
(In reply to hsteoh from comment #35)
> @Andrei: any @safe function can call a @trusted function that may contain
> arbitrary unsafe operations. Just because something is marked @safe at the
> top guarantees nothing.

This is a misunderstanding of what @trusted is. It's very important that we
clear this up.

Your misunderstanding seems to be that the CALLER of @trusted code must be
careful to use it safely. This is incorrect. @trusted code needs to be
reviewable for safety by ONLY looking at the @trusted code body. NOT the way
the @trusted code is used. For example:

  @trusted void foo() {
    auto p = malloc(3);
    free(p);
  }

is correct use of trust. The following is incorrect:

  @trusted void* tmalloc(size_t n) { return malloc(n); }
  @trusted void tfree(void* p) { return free(p);

  @safe void foo() {
    auto p = tmalloc(3);
    tfree(p);
  }

Make sense?

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