FlexibleTypes are not handled in Quotes

[WojciechMazur]

Issue found in OpenCB for scalacenter/tasty-mima - build logs

Compiler version

3.5.0-RC1-bin-20240417-b93c337-NIGHTLY

Minimized code

Not minimized yet

Output

Error:  -- Error: /build/repo/tasty-mima/src/test/scala/tastymima/intf/ProblemSuite.scala:41:18 
Error:  41 |      assert(clue(TestProblem(kind, "<path-string>").getFilterIncantation()) == clue(expected))
Error:     |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Error:     |Exception occurred while executing macro expansion.
Error:     |scala.MatchError: FlexibleType(OrType(TypeRef(ThisType(TypeRef(NoPrefix,module class lang)),class String),TypeRef(ThisType(TypeRef(NoPrefix,module class scala)),class Null)),TypeRef(ThisType(TypeRef(NoPrefix,module class lang)),class String)) (of class dotty.tools.dotc.core.Types$FlexibleType)
Error:     |	at scala.quoted.runtime.impl.printers.Extractors$ExtractorsPrinter.visitType(Extractors.scala:241)
Error:     |	at scala.quoted.runtime.impl.printers.Extractors$.showType(Extractors.scala:12)
Error:     |	at scala.quoted.runtime.impl.QuotesImpl$$anon$19.show(QuotesImpl.scala:3219)
Error:     |	at scala.quoted.runtime.impl.QuotesImpl$$anon$19.show(QuotesImpl.scala:3218)
Error:     |	at scala.quoted.runtime.impl.QuotesImpl$reflect$TypeReprMethods$.show(QuotesImpl.scala:1804)
Error:     |	at scala.quoted.runtime.impl.QuotesImpl$reflect$TypeReprMethods$.show(QuotesImpl.scala:1804)
Error:     |	at scala.quoted.runtime.impl.printers.SourceCode$SourceCodePrinter.printType(SourceCode.scala:1251)
Error:     |	at scala.quoted.runtime.impl.printers.SourceCode$SourceCodePrinter.printTypeAndAnnots$1(SourceCode.scala:1020)
Error:     |	at scala.quoted.runtime.impl.printers.SourceCode$SourceCodePrinter.printTypeTree(SourceCode.scala:1022)
Error:     |	at scala.quoted.runtime.impl.printers.SourceCode$SourceCodePrinter.printTree(SourceCode.scala:527)
Error:     |	at scala.quoted.runtime.impl.printers.SourceCode$.showTree(SourceCode.scala:10)
Error:     |	at scala.quoted.runtime.impl.QuotesImpl$$anon$13.show(QuotesImpl.scala:3195)
Error:     |	at scala.quoted.runtime.impl.QuotesImpl$$anon$13.show(QuotesImpl.scala:3194)
Error:     |	at scala.quoted.runtime.impl.QuotesImpl$reflect$TreeMethods$.show(QuotesImpl.scala:108)
Error:     |	at scala.quoted.runtime.impl.QuotesImpl$reflect$TreeMethods$.show(QuotesImpl.scala:108)
Error:     |	at munit.internal.MacroCompat$.clueImpl(MacroCompat.scala:31)
Error:     |
Error:     |----------------------------------------------------------------------------
Error:     |Inline stack trace
Error:     |- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Error:     |This location contains code that was inlined from MacroCompat.scala:24
Error:      ----------------------------------------------------------------------------```

Expectation

Audit and fix the corner cases where FlexibleType might lead to MatchError

[noti0na1]

To fix the missing case, we have to add flexible types to Quotes library.