Local imports hide local symbols

[H. S. Teoh via Digitalmars-d]

On Tue, Sep 23, 2014 at 06:56:56PM +0000, Meta via Digitalmars-d wrote:
> On Tuesday, 23 September 2014 at 18:52:13 UTC, H. S. Teoh via Digitalmars-d
> wrote:
> >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
> 
> The only tenable option from that list seems to be 1. 2 and 2b either
> compile or not depending on the implementation details of the module
> (i.e., add a symbol i to a module and it may break code in an entirely
> different module that imports your module), and 3 will break a lot of
> valid code.

Good luck convincing Walter, then. :-(  Or maybe if we can convince
Andrei to twist his arm hard enough... :-P


T

-- 
Живёшь только однажды.