Make std.stdio.File.error and flush @trusted
Mark std.exception.ErrnoException.this as @trusted
Add missing imports
Merge pull request #1999 from monarchdodra/rangeImport

Missing imports in range
Merge pull request #1998 from tom-tan/trusted-exception-ErrnoException-this

Mark std.exception.ErrnoException.this as @trusted
Tweak map's save

Not only does it avoid opAssign issues, but the final code is simpler anyways.
Remove unnecessary enforce
Add test-cases for Issue 12349
Merge pull request #1997 from tom-tan/trusted-std-stdio-File-error-flush

std.File.flush and error causes segfault after calling close
Merge pull request #2000 from monarchdodra/mapSave

Tweak map's save