Fix bug 18079 - rdmd does not discover all dependencies

[marler8997]

Fix for issue https://issues.dlang.org/show_bug.cgi?id=18079

This will result in a known performance decrease but this is unavoidable unless we can modify rdmd to invoke dmd 1 time instead of 2.

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Bugzilla references

Auto-close	Bugzilla	Description
✓	18079	rdmd does not discover all dependencies

[timotheecour]

indeed, on a simple test using time command, simply adding -deps kills performance. This defeats purpose of this PR and justifies the need for #271

time rdmd --force --extra-file=fun2.d --extra-file=fun2.d --extra-file=fun3.d -deps=/tmp/z01.txt main.d

0.74s user 0.13s system 98% cpu 0.883 total

time rdmd --force --extra-file=fun2.d --extra-file=fun2.d --extra-file=fun3.d main.d
 0.12s user 0.04s system 94% cpu 0.172 total

[timotheecour]

NOTE: just filed this bug, it prevents this PR from working at all currently: https://issues.dlang.org/show_bug.cgi?id=18271

[marler8997]

I think this may be by design. It only performs the full semantic analysis on modules imported by the first module given on the command line. I remember seeing the code do this and I thought it was odd but I assumed there was a reason for this.

[marler8997]

https://github.com/dlang/dmd/blob/f947c0881432988dcd8cd80d5abe71e4c0463867/src/dmd/mars.d#L822

This is where the extra semantic analysis is done when the -deps flag is used. As you can see, only module[0].aimports is being scanned. This is either a bug or by design. If it's a bug, then the fix is likely to loop over Modules.modules instead of modules[0].aimports.

[timotheecour]

thanks, replied directly on bug report (https://issues.dlang.org/show_bug.cgi?id=18271#c2) to keep that side discussion separate