[Issue 12605] New: Calculate proper common type of lambdas

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=12605

          Issue ID: 12605
           Summary: Calculate proper common type of lambdas
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: DMD
          Assignee: nobody at puremagic.com
          Reporter: k.hara.pg at gmail.com

Currently this code:

pragma(msg, typeof(true ? (x => x) : ((int x) => x * 2)));

prints 'void'. But it could print 'int function(int)' by fitting parameter
types.

More cases:

pragma(msg, typeof(true ? (()=>1) : (()=>1.0)));
// fitting return types - could be 'double function()'

pragma(msg, typeof(true ? ((int x) => 1) : (delegate(int x)=>1)));
// fitting context type --> could be 'int delegate(int)'

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