Prevent crash in SAM conversion with mismatched arity

[nox213]

closes #23577

[sjrd]

From the doc of the enclosing function, it seems we should return a wildcard type when a type is not known, hence:

Suggested change

	untpd.TypeTree()
	typeTree(WildcardType)

[nox213]

880fc84
Thank you for your review. Could you tell me where I can find the doc?

[sjrd]

Could you add an i123577.check file to ensure that the displayed error is meaningful?

[nox213]

880fc84

[sjrd]

Looks good now. Would you mind squashing all the commits into one with a clean commit message? Right now that's a lot of messy commits for so few lines of code changes :p

[nox213]

Done!

[nox213]

-- Error: tests/pos-custom-args/captures/check-override-typebounds-2.scala:6:23 ----------------------------------------
6 |  type T <: Capbility^{caps.cap.rd}
  |                       ^^^^^^^^^^^
  |                       cap.rd cannot be tracked since its capture set is empty
  |
  |                       where:    cap is the universal root capability
-- Error: tests/pos-custom-args/captures/check-override-typebounds-2.scala:9:14 ----------------------------------------
9 |  type T = C^{caps.cap.rd}
  |              ^^^^^^^^^^^
  |              cap.rd cannot be tracked since its capture set is empty
  |
  |              where:    cap is the universal root capability
Compilation failed for: 'tests/pos-custom-args/captures/check-override-typebounds-2.scala'
Error:  Test dotty.tools.dotc.CompilationTests.pos failed: java.lang.AssertionError: Pos test failed, but should not, reasons:
Error:  encountered 1 test failure(s):
Error:    - generic failure (see test output), took 94.582 sec
Error:      at dotty.tools.vulpix.ParallelTesting$CompilationTest.checkPass(ParallelTesting.scala:1269)
Error:      at dotty.tools.vulpix.ParallelTesting$CompilationTest.checkCompile(ParallelTesting.scala:1185)
Error:      at dotty.tools.dotc.CompilationTests.pos(CompilationTests.scala:56)
Error:      at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
Error:      at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
Error:      at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
Error:      at java.lang.reflect.Method.invoke(Method.java:569)
Error:      ...

I don’t see why it failed. testCompilation passed on my machine, and it had also passed in the previous run.

[nox213]

Is this good to merge? auto-merge wasn't triggered because of failure(it passed after rerun)