700802 - Make JSLinearString::ensureLinear (mutatis mutandis for JSFlatString and other subtypes, and for is* and as* methods) a compile error

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Jeff Walden [:Waldo]]

Attachment: Patch

It's perfectly legal to call ensureLinear on a linear string right now.  It's also completely pointless.  We can make it a compile error so that this can't be done.  This sort of mistake is most likely to bite changes that improve typing of a class member (say, from JSString to JSLinearString), although I could imagine it happening if someone suffered a brief memory lapse when writing some other patch.

Comment 1

[Jeff Walden [:Waldo]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/85f790b1de47

Earlier this year C++11 had a declaration modifier, "new", which could be used to require that a declarator in a class hide an identically-typed declarator in a superclass.  It got taken out because the ISO people were running out of places to shoehorn it, for non-method declarator syntax.  Le sigh; that would have been perfect for these uses.

http://stackoverflow.com/questions/5530022/override-non-virtual-functions-in-c-2011

Oh well, this will likely work well enough.

Comment 2

[Marco Bonardo [:mak]]

https://hg.mozilla.org/mozilla-central/rev/85f790b1de47