[Issue 19879] New: std.concurrency: Emit offending field name when failing to spawn() with mutable thread-local data

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=19879

          Issue ID: 19879
           Summary: std.concurrency: Emit offending field name when
                    failing to spawn() with mutable thread-local data
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: phobos
          Assignee: nobody at puremagic.com
          Reporter: andrej.mitrovich at gmail.com

This message should be improved:

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/usr/local/opt/dmd/include/dlang/dmd/std/concurrency.d(449,5): Error: static
assert:  "Aliases to mutable thread-local data not allowed."
mod.d(171,30):        instantiated from here: `spawn!(void function(Config)
@system, Config)`
mod2.d(48,25):        instantiated from here: `__ctor!(Config)`
-----

It doesn't say which field is the offending one, just that there is some
pointer or array somewhere, but it's really hard to determine what is the
offending field when the data structure is complex.

With all the traits power D has, emitting the field name should be possible.

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