A reminder about this common idiom:

switch (...) {
case Foo:
    return ...;
case Bar:
    return ...;
}
RELEASE_ASSERT_NOT_REACHED();

When it's intended that the code always returns inside the switch 
statement, the RELEASE_ASSERT_NOT_REACHED() is required to avoid 
tripping GCC's -Wreturn-type. If you forget it, I or somebody else will 
wind up adding it later to avoid the warning. Clang does not warn here, 
and this is the most common type of warning I clean up, so please don't 
forget! :) This warning is useful in other situations, and it seems 
nicer to placate GCC than to disable it.

I'll sneak in another reminder: "return WTFMove()" is almost always not 
needed. Clang warns only if the move prevents return value 
optimization, but GCC will always warn if it detects the move is 
unneeded.