Function with invalid argument type crash (parser stability)

## minimized code

```Scala
def foo = (x: @) => ()
```


<details>
<summary>Stack trace</summary>

```scala
-- [E040] Syntax Error: testing/Test.scala:1:15 --------------------------------
1 |def foo = (x: @) => ()
  |               ^
  |               an identifier expected, but ')' found
exception occurred while typechecking testing/Test.scala
exception occurred while compiling testing/Test.scala
java.lang.AssertionError: assertion failed while compiling testing/Test.scala
Exception in thread "main" java.lang.AssertionError: assertion failed
	at dotty.DottyPredef$.assertFail(DottyPredef.scala:16)
	at dotty.tools.dotc.typer.TypeAssigner.assignType(TypeAssigner.scala:622)
	at dotty.tools.dotc.typer.Typer.assignType(Typer.scala:83)
	at dotty.tools.dotc.typer.Typer.typedAnnotated(Typer.scala:1925)
	at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:2151)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2177)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2213)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2225)
	at dotty.tools.dotc.typer.Namer.typedAheadType$$anonfun$1(Namer.scala:1260)
	at dotty.tools.dotc.typer.Namer.typedAhead(Namer.scala:1253)
	at dotty.tools.dotc.typer.Namer.typedAheadType(Namer.scala:1260)
	at dotty.tools.dotc.typer.Namer.valOrDefDefSig(Namer.scala:1449)
	at dotty.tools.dotc.typer.Namer$Completer.typeSig(Namer.scala:811)
	at dotty.tools.dotc.typer.Namer$Completer.completeInCreationContext(Namer.scala:935)
	at dotty.tools.dotc.typer.Namer$Completer.complete(Namer.scala:843)
	at dotty.tools.dotc.core.SymDenotations$SymDenotation.completeFrom(SymDenotations.scala:258)
	at dotty.tools.dotc.core.Denotations$Denotation.completeInfo$1(Denotations.scala:185)
	at dotty.tools.dotc.core.Denotations$Denotation.info(Denotations.scala:187)
	at dotty.tools.dotc.core.SymDenotations$SymDenotation.ensureCompleted(SymDenotations.scala:398)
	at dotty.tools.dotc.typer.Typer.retrieveSym(Typer.scala:2071)
	at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:2096)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2176)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2213)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2225)
	at dotty.tools.dotc.typer.Namer.typedAheadExpr$$anonfun$1(Namer.scala:1263)
	at dotty.tools.dotc.typer.Namer.typedAhead(Namer.scala:1253)
	at dotty.tools.dotc.typer.Namer.typedAheadExpr(Namer.scala:1263)
	at dotty.tools.dotc.typer.Namer.completeParams$$anonfun$1(Namer.scala:1278)
	at scala.collection.immutable.List.foreach(List.scala:305)
	at dotty.tools.dotc.typer.Namer.completeParams(Namer.scala:1278)
	at dotty.tools.dotc.typer.Namer.defDefSig$$anonfun$3(Namer.scala:1488)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at scala.collection.immutable.List.foreach(List.scala:305)
	at dotty.tools.dotc.typer.Namer.defDefSig(Namer.scala:1488)
	at dotty.tools.dotc.typer.Namer$Completer.typeSig(Namer.scala:815)
	at dotty.tools.dotc.typer.Namer$Completer.completeInCreationContext(Namer.scala:935)
	at dotty.tools.dotc.typer.Namer$Completer.complete(Namer.scala:843)
	at dotty.tools.dotc.core.SymDenotations$SymDenotation.completeFrom(SymDenotations.scala:258)
	at dotty.tools.dotc.core.Denotations$Denotation.completeInfo$1(Denotations.scala:185)
	at dotty.tools.dotc.core.Denotations$Denotation.info(Denotations.scala:187)
	at dotty.tools.dotc.core.SymDenotations$SymDenotation.ensureCompleted(SymDenotations.scala:398)
	at dotty.tools.dotc.typer.Typer.retrieveSym(Typer.scala:2071)
	at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:2096)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2176)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2213)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2225)
	at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:2247)
	at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:2291)
	at dotty.tools.dotc.typer.Typer.typedBlockStats(Typer.scala:785)
	at dotty.tools.dotc.typer.Typer.typedBlock(Typer.scala:789)
	at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:2127)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2177)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2213)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2225)
	at dotty.tools.dotc.typer.Typer.typedFunctionValue(Typer.scala:1077)
	at dotty.tools.dotc.typer.Typer.typedFunction(Typer.scala:903)
	at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:2129)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2177)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2213)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2225)
	at dotty.tools.dotc.typer.Namer.typedAheadExpr$$anonfun$1(Namer.scala:1263)
	at dotty.tools.dotc.typer.Namer.typedAhead(Namer.scala:1253)
	at dotty.tools.dotc.typer.Namer.typedAheadExpr(Namer.scala:1263)
	at dotty.tools.dotc.typer.Namer.rhsType$2(Namer.scala:1397)
	at dotty.tools.dotc.typer.Namer.cookedRhsType$1(Namer.scala:1408)
	at dotty.tools.dotc.typer.Namer.lhsType$1(Namer.scala:1409)
	at dotty.tools.dotc.typer.Namer.inferredType$1(Namer.scala:1420)
	at dotty.tools.dotc.typer.Namer.valOrDefDefSig(Namer.scala:1428)
	at dotty.tools.dotc.typer.Namer.defDefSig(Namer.scala:1500)
	at dotty.tools.dotc.typer.Namer$Completer.typeSig(Namer.scala:815)
	at dotty.tools.dotc.typer.Namer$Completer.completeInCreationContext(Namer.scala:935)
	at dotty.tools.dotc.typer.Namer$Completer.complete(Namer.scala:843)
	at dotty.tools.dotc.core.SymDenotations$SymDenotation.completeFrom(SymDenotations.scala:258)
	at dotty.tools.dotc.core.Denotations$Denotation.completeInfo$1(Denotations.scala:185)
	at dotty.tools.dotc.core.Denotations$Denotation.info(Denotations.scala:187)
	at dotty.tools.dotc.core.SymDenotations$SymDenotation.ensureCompleted(SymDenotations.scala:398)
	at dotty.tools.dotc.typer.Typer.retrieveSym(Typer.scala:2071)
	at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:2096)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2176)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2213)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2225)
	at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:2247)
	at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:2291)
	at dotty.tools.dotc.typer.Typer.typedClassDef(Typer.scala:1784)
	at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:2109)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2176)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2213)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2225)
	at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:2247)
	at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:2291)
	at dotty.tools.dotc.typer.Typer.typedPackageDef(Typer.scala:1910)
	at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:2150)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2177)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2213)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2225)
	at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:2333)
	at dotty.tools.dotc.typer.FrontEnd.liftedTree1$2(FrontEnd.scala:78)
	at dotty.tools.dotc.typer.FrontEnd.typeCheck$$anonfun$1(FrontEnd.scala:83)
	at dotty.runtime.function.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
	at dotty.tools.dotc.typer.FrontEnd.monitor(FrontEnd.scala:42)
	at dotty.tools.dotc.typer.FrontEnd.typeCheck(FrontEnd.scala:84)
	at dotty.tools.dotc.typer.FrontEnd.runOn$$anonfun$3(FrontEnd.scala:114)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at scala.collection.immutable.List.foreach(List.scala:305)
	at dotty.tools.dotc.typer.FrontEnd.runOn(FrontEnd.scala:114)
	at dotty.tools.dotc.Run.runPhases$4$$anonfun$4(Run.scala:161)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1323)
	at dotty.tools.dotc.Run.runPhases$5(Run.scala:171)
	at dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:179)
	at dotty.runtime.function.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
	at dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:65)
	at dotty.tools.dotc.Run.compileUnits(Run.scala:186)
	at dotty.tools.dotc.Run.compileSources(Run.scala:123)
	at dotty.tools.dotc.Run.compile(Run.scala:106)
	at dotty.tools.dotc.Driver.doCompile(Driver.scala:36)
	at dotty.tools.dotc.Driver.process(Driver.scala:189)
	at dotty.tools.dotc.Driver.process(Driver.scala:158)
	at dotty.tools.dotc.Driver.process(Driver.scala:170)
	at dotty.tools.dotc.Driver.main(Driver.scala:197)
	at dotty.tools.dotc.Main.main(Main.scala)
```
</details>


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Function with invalid argument type crash (parser stability) #7818

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Function with invalid argument type crash (parser stability) #7818

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minimized code

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Metadata

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Development

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