digitalmars.D.bugs - [Issue 17951] New: Deprecate Shorthand Lambda Followed by Brace
- d-bugmail puremagic.com (36/36) Oct 29 2017 https://issues.dlang.org/show_bug.cgi?id=17951
https://issues.dlang.org/show_bug.cgi?id=17951 Issue ID: 17951 Summary: Deprecate Shorthand Lambda Followed by Brace Product: D Version: D2 Hardware: All OS: All Status: NEW Severity: enhancement Priority: P1 Component: dmd Assignee: nobody puremagic.com Reporter: qs.il.paperinik gmail.com Disallow braced lambda after =>. Concrete, for the D grammar people, if in a Lambda the arrow is followed by a FunctionLiteral which is just a FunctionLiteralBody, this will be an error. It applies not when the function after => is called, e.g. (..) => { .. }(), because then the "thing" after => is a PostfixExpression (as is any function call), not a FunctionLiteralBody.[1] workarounds are simple: 1. Use () before the brace. 2. Use function/delegate before the brace 3. Use braces instead of =>, e.g. (..) { return { .. }; } instead of (..) => { .. } The compiler should warn you that => { .. } introduces two nested lambdas and because probably one actually wants just one, suggests to delete the arrow. In case of desired nested lambdas, the recommended fix is 2. to make it obvious to anyone reading the code. Option 1. is possible but not that desirable. Option 3 should definitely not be recommended by the compiler as it is very lengthy. [1] https://dlang.org/spec/expression.html#FunctionLiteral As this is potentially breaking code, we'd need the full deprecation process. Fortunately, nested lambdas are rarely used, so the amount of broken code is small if any. --
Oct 29 2017