[Issue 24525] auto ref lambda exp not parsed if used as left-most expression in a expression statement

[Issue 24525] auto ref lambda exp not parsed if used as left-most expression in an expression statement

Apr 29

basile-z

Apr 30

Nick Treleaven

May 01

Dlang Bot

May 02

Dlang Bot

https://issues.dlang.org/show_bug.cgi?id=24525 Nick Treleaven <nick@geany.org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |nick@geany.org Severity|normal |enhancement --- Comment #1 from Nick Treleaven <nick@geany.org> --- Under https://dlang.org/spec/statement.html#NonEmptyStatementNoCaseNoDefault grammar block it says: > Any ambiguities in the grammar between Statements and Declarations are resolved by the declarations taking precedence. For: > ref () {return a;}() = 0; A declaration `ref () {return a;}` gets parsed, not an ExpressionStatement. So I think this issue is invalid. It is unfortunate that the function literal syntax starting `ref` or `auto ref` was added, when the function/delegate keyword starting forms can already handle those. --

April 29

[Issue 24525] auto ref lambda exp not parsed if used as left-most expression in a expression statement

Posted by basile-z

Permalink

basile-z

Permalink

https://issues.dlang.org/show_bug.cgi?id=24525

--- Comment #3 from basile-z <b2.temp@gmx.com> ---
> Any ambiguities in the grammar between Statements and Declarations are resolved by the declarations taking precedence.

yes, I remember the spec about decl/stmt ambiguities but here I think there are none.

The parser should lookup after `auto`. If next is `(` or if next two are `ref` then `(`, then it should takes the path of expression.

> It is unfortunate that the function literal syntax starting `ref` or `auto ref` was added, when the function/delegate keyword starting forms can already handle those.

Indeed. But I'll show you the context:

```
void main()
{
    int a,b,c,d,cond;

    auto ref () {
        switch (cond)
        {
            case 1: return a;
            case 2: return b;
            case 3: return c;
            default: return d;
        }
    }() = 0;
}
```

Here, given the size of the lambda, you try to avoid the verbose solution (you can put the lambda between parens however, but according to the specs, that should work w/o).

--

https://issues.dlang.org/show_bug.cgi?id=24525 Dlang Bot <dlang-bot@dlang.rocks> changed: What |Removed |Added ---------------------------------------------------------------------------- Keywords| |pull --- Comment #4 from Dlang Bot <dlang-bot@dlang.rocks> --- @ntrel created dlang/dmd pull request #16431 "Fix Bugzilla 24525 - ref lambda not parsed at start of ExpressionStat…" fixing this issue: - Fix Bugzilla 24525 - ref lambda not parsed at start of ExpressionStatement https://github.com/dlang/dmd/pull/16431 --

https://issues.dlang.org/show_bug.cgi?id=24525 Dlang Bot <dlang-bot@dlang.rocks> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |RESOLVED Resolution|--- |FIXED --- Comment #5 from Dlang Bot <dlang-bot@dlang.rocks> --- dlang/dmd pull request #16431 "Fix Bugzilla 24525 - ref lambda not parsed at start of ExpressionStat…" was merged into master: - 3c3be0716da1b6d2cdbe2ca6517a8b1cec6d7ae2 by Nick Treleaven: Fix Bugzilla 24525 - ref lambda not parsed at start of ExpressionStatement https://github.com/dlang/dmd/pull/16431 --

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