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

[dlangBugzillaToGithub]

andrej.mitrovich (@AndrejMitrovic) reported this on 2019-05-16T08:46:41Z

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

Description

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)`
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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.

[dlangBugzillaToGithub]

andrej.mitrovich (@AndrejMitrovic) commented on 2019-06-17T06:42:21Z

Alternative:

Make the ` hasLocalAliasing` function public. That way we can add the check to composite types on our own.

[dlangBugzillaToGithub]

andrej.mitrovich (@AndrejMitrovic) commented on 2019-06-17T06:43:09Z

Actually I've just noticed it just uses std.traits.hasUnsharedAliasing internally, so never mind about the last suggestion.