Local imports hide local symbols

[H. S. Teoh via Digitalmars-d]

On Tue, Sep 23, 2014 at 11:34:51AM -0700, Andrei Alexandrescu via Digitalmars-d wrote:
> I've raised https://issues.dlang.org/show_bug.cgi?id=10378 to critical.
> Please chime in with ideas for a good solution. Thanks! -- Andrei

I can think of a few:

1) Change lookup rules so that symbols pulled in by local import are
found last. Walter has stated that he disagrees with this approach
because it complicates symbol lookup rules.

2) Emit a compile error if any symbol pulled in by the local import
shadows a symbol currently in scope, according to the same rules as
declaring local variables that shadow identically-named variables in an
outer scope within the current function body.

3) What you proposed in the bugnotes: only allow `static import xyz;`
and `import xyz : a, b, c;` at local scope.

As far as breakage of existing code is concerned, (1) and (2) will only
break code where there was already a problem (an outer scope's symbol is
being shadowed, most likely unintentionally, by the import). (3) will
likely cause backlash because it will break a LOT of code that currently
compiles and likely to have no actual problems. Not to mention that
while naming specific symbols to import works for trivial cases, it can
quickly and easily devolve into inordinately long lists of symbols once
the local scope grows into non-trivial code. People are unlikely to be
happy with this.

Which leads to this variation of (2):

2b) Allow unqualified `import xyz;` in local scope, but only if NONE of
the imported symbols shadows ANY symbol visible from that scope.


T

-- 
"Holy war is an oxymoron." -- Lazarus Long