[SR-6384] Adding parameter with default value fails with linker error

[NachoSoto]

Previous ID	SR-6384
Radar	None
Original Reporter	@NachoSoto
Type	Bug

Environment

Xcode Version 9.1 (9B55)
Swift version 4.0.2 (swiftlang-900.0.69.1 clang-900.0.38)

Additional Detail from JIRA

Votes	0
Component/s	Compiler
Labels	Bug
Assignee	None
Priority	Medium

md5: 8cb41ae2b88353d7b3a39229de2db80c

Issue Description:

Scenario:

Module A:

public final class C {
  public init(a: Int) {}
}

Module B:

func f() {
  let _ = C(a: 0)
}

Upon compiling this, I changed module A:

class C {
  init(a: Int, b: Bool = false) {}
}

Expected result:

Incremental compilation leads to Module B getting recompiled (or whatever needs to happen), and things work.

Actual result:

Undefined symbols for architecture arm64:
  "__T02UI12CardCellViewCACSb13displayShadow_SC6CGRectV12initialFrameSb6cached12CoreGraphics7CGFloatV7paddingtcfC", referenced from:
      __T02UI15CardLibraryCell33_2ABB1494CE3CB6681FDE7B05F9E507C1LLCADSC6CGRectV5frame_tcfc in CardDashboardViewController.o
      __T02UI16CombinedCardViewC04cardD033_0290C3EDF9FFAA02DAA34A4BAEC3322DLLAA0c4CellD0CfgAGycfU_ in CombinedCardView.o
  "__T02UI12CardCellViewCACSb13displayShadow_SC6CGRectV12initialFrameSb6cached12CoreGraphics7CGFloatV7paddingtcfcfA1_", referenced from:
      __T02UI15CardLibraryCell33_2ABB1494CE3CB6681FDE7B05F9E507C1LLCADSC6CGRectV5frame_tcfc in CardDashboardViewController.o
      __T02UI16CombinedCardViewC04cardD033_0290C3EDF9FFAA02DAA34A4BAEC3322DLLAA0c4CellD0CfgAGycfU_ in CombinedCardView.o
  "__T02UI12CardCellViewCACSb13displayShadow_SC6CGRectV12initialFrameSb6cached12CoreGraphics7CGFloatV7paddingtcfcfA2_", referenced from:
      __T02UI15CardLibraryCell33_2ABB1494CE3CB6681FDE7B05F9E507C1LLCADSC6CGRectV5frame_tcfc in CardDashboardViewController.o
      __T02UI16CombinedCardViewC04cardD033_0290C3EDF9FFAA02DAA34A4BAEC3322DLLAA0c4CellD0CfgAGycfU_ in CombinedCardView.o
ld: symbol(s) not found for architecture arm64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

(Obviously those are from the real example). Module B didn't see the change, because the invocation to C(a: 0) was still valid, leading to a linker error.

Note: this is similar to SR-1171, which is probably still an issue.

[belkadan]

Can you reproduce this in a standalone example? The above code can't be what you were using because there are no public annotations in it.

[NachoSoto]

I haven't tried. As seen in my error, that's from my real project. I updated the example to add public annotations.
I don't have time to re-create a sample project though, but I'm 100% confident in the steps I took to reproduce this.

[belkadan]

Mmk, thanks.