The test class `KeywordFieldMapperTests` contains a switch statement with a branch that will never execute. The test uses a `between(x, y)` switch expression, but the `4` case is outside the randomised range. We need to fix this before #88739 can be merged. By "fix", I mean either remove the spurious case, or if we actually want it then extend the randomized range.
server/src/test/java/org/elasticsearch/index/mapper/KeywordFieldMapperTests.java
public void testScriptAndPrecludedParameters() {
        Exception e = expectThrows(MapperParsingException.class, () -> createDocumentMapper(fieldMapping(b -> {
            b.field("type", "keyword");
            b.field("script", "test");
            b.field("null_value", true);
        })));
        assertThat(e.getMessage(), equalTo("Failed to parse mapping: Field [null_value] cannot be set in conjunction with field [script]"));
    }
    @Override
    protected Object generateRandomInputValue(MappedFieldType ft) {
        return switch (between(0, 3)) {
            case 0 -> randomAlphaOfLengthBetween(1, 100);
            case 1 -> randomBoolean() ? null : randomAlphaOfLengthBetween(1, 100);
            case 2 -> randomLong();
            case 3 -> randomDouble();
            case 4 -> randomBoolean();
            default -> throw new IllegalStateException();
        };
    }
    @Override
    protected boolean dedupAfterFetch() {
        return true;
    }
    @Override
    protected String minimalIsInvalidRoutingPathErrorMessage(Mapper mapper) {
        return "All fields that match routing_path must be keywords with [time_series_dimension: true] "
            + "and without the [script] parameter. ["
            + mapper.name()
            + "] was not [time_series_dimension: true].";
    }