I came across an UnsupportedOperationException like the following when experimenting with parsing switch expressions:

java.lang.UnsupportedOperationException: com.github.javaparser.ast.expr.SwitchExpr
	at com.github.javaparser.symbolsolver.javaparsermodel.DefaultVisitorAdapter.visit(DefaultVisitorAdapter.java:530)
	at com.github.javaparser.symbolsolver.javaparsermodel.DefaultVisitorAdapter.visit(DefaultVisitorAdapter.java:37)
	at com.github.javaparser.ast.expr.SwitchExpr.accept(SwitchExpr.java:90)
	at com.github.javaparser.symbolsolver.javaparsermodel.JavaParserFacade.getTypeConcrete(JavaParserFacade.java:670)
	at com.github.javaparser.symbolsolver.javaparsermodel.JavaParserFacade.getType(JavaParserFacade.java:424)
	at com.github.javaparser.symbolsolver.javaparsermodel.JavaParserFacade.getType(JavaParserFacade.java:389)
	at com.github.javaparser.symbolsolver.JavaSymbolSolver.calculateType(JavaSymbolSolver.java:443)

The cause was that the TypeExtractor did not implement the type extraction for switch expressions. For example, I had a case like this which threw the exception because the type of the method call argument (the result of the switch expression) could not be computed:

    methodCall(
        switch ("a") {
          case "a" -> 3;
          default -> 0;
        });

The PR implements:

• Type extraction for switch expressions based on JLS 15.28.1

Otherwise, if the type of each result expression is boolean or Boolean, then an unboxing conversion (§5.1.8) is applied to each result expression of type Boolean, and the switch expression has type boolean.

Otherwise, if the type of each result expression is convertible to a numeric type ( §5.1.8), then the type of the switch expression is the result of general numeric promotion (§5.6) applied to the result expressions.

Otherwise, boxing conversion (§5.1.7 ) is applied to each result expression that has a primitive type, after which the type of the switch expression is the result of applying capture conversion (§5.1.10) to the least upper bound (§4.10.4) of the types of the result expressions.

• Validation for switch expressions with no result expressions based on 15.28.1