Handle assertion error in TyperState #23665
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scala#23609 triggers an assertion error in TyperState. The relevant explanation seems to be in ProtoTypes.scala: ```scala // To respect the pre-condition of `mergeConstraintWith` and keep // `protoTyperState` committable we must ensure that it does not // contain any type variable which don't already exist in the passed // TyperState. This is achieved by instantiating any such type // variable. NOTE: this does not suffice to discard type variables // in ancestors of `protoTyperState`, if this situation ever // comes up, an assertion in TyperState will trigger and this code // will need to be generalized. ``` We should go to the bottom of it and fix the assertion. But before that's done this PR offers a temporary hack to catch the exception when it is triggered from a new code path created by PR scala#23532. This should fix the regression reported in scala#23609. We should leave the issue open as a reminder that we still need a better fix. Also: handle crash to missing span in a migration helper.
WojciechMazur
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Aug 5, 2025
tgodzik
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to scala/scala3-lts
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Aug 28, 2025
explanation seems to be in ProtoTypes.scala:
```scala
// To respect the pre-condition of `mergeConstraintWith` and keep
// `protoTyperState` committable we must ensure that it does not
// contain any type variable which don't already exist in the passed
// TyperState. This is achieved by instantiating any such type
// variable. NOTE: this does not suffice to discard type variables
// in ancestors of `protoTyperState`, if this situation ever
// comes up, an assertion in TyperState will trigger and this code
// will need to be generalized.
```
We should go to the bottom of it and fix the assertion. But before
that's done this PR offers a temporary hack to catch the exception when
it is triggered from a new code path created by PR scala#23532. This should
fix the regression reported in scala#23609. We should leave the issue open as
a reminder that we still need a better fix.
Also: handle crash due to missing span in a migration helper.
tgodzik
added a commit
to scala/scala3-lts
that referenced
this pull request
Aug 28, 2025
scala#23609 triggers an assertion error in TyperState. The relevant explanation seems to be in ProtoTypes.scala: ```scala // To respect the pre-condition of `mergeConstraintWith` and keep // `protoTyperState` committable we must ensure that it does not // contain any type variable which don't already exist in the passed // TyperState. This is achieved by instantiating any such type // variable. NOTE: this does not suffice to discard type variables // in ancestors of `protoTyperState`, if this situation ever // comes up, an assertion in TyperState will trigger and this code // will need to be generalized. ``` We should go to the bottom of it and fix the assertion. But before that's done this PR offers a temporary hack to catch the exception when it is triggered from a new code path created by PR scala#23532. This should fix the regression reported in scala#23609. We should leave the issue open as a reminder that we still need a better fix. Also: handle crash due to missing span in a migration helper. [Cherry-picked 408298d][modified]
WojciechMazur
pushed a commit
that referenced
this pull request
Sep 22, 2025
#23609 triggers an assertion error in TyperState. The relevant explanation seems to be in ProtoTypes.scala: ```scala // To respect the pre-condition of `mergeConstraintWith` and keep // `protoTyperState` committable we must ensure that it does not // contain any type variable which don't already exist in the passed // TyperState. This is achieved by instantiating any such type // variable. NOTE: this does not suffice to discard type variables // in ancestors of `protoTyperState`, if this situation ever // comes up, an assertion in TyperState will trigger and this code // will need to be generalized. ``` We should go to the bottom of it and fix the assertion. But before that's done this PR offers a temporary hack to catch the exception when it is triggered from a new code path created by PR #23532. This should fix the regression reported in #23609. We should leave the issue open as a reminder that we still need a better fix. Also: handle crash due to missing span in a migration helper. [Cherry-picked 408298d]
WojciechMazur
added a commit
that referenced
this pull request
Sep 23, 2025
Backports #23665 to the 3.7.4. PR submitted by the release tooling. [skip ci]
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#23609 triggers an assertion error in TyperState. The relevant explanation seems to be in ProtoTypes.scala:
We should go to the bottom of it and fix the assertion. But before that's done this PR offers a temporary hack to catch the exception when it is triggered from a new code path created by PR #23532. This should fix the regression reported in #23609. We should leave the issue open as a reminder that we still need a better fix.
Also: handle crash due to missing span in a migration helper.