```
from employees | keep * | mv_expand first_name
```

throws UnresolvedException:

```
org.elasticsearch.xpack.ql.capabilities.UnresolvedException: Invalid call to attribute on an unresolved object ?*
        at org.elasticsearch.xpack.ql.expression.UnresolvedNamedExpression.toAttribute(UnresolvedNamedExpression.java:44)
        at org.elasticsearch.xpack.ql.expression.Expressions.asAttributes(Expressions.java:40)
        at org.elasticsearch.xpack.ql.plan.logical.Project.output(Project.java:62)
        at org.elasticsearch.xpack.esql.plan.logical.MvExpand.<init>(MvExpand.java:31)
        at org.elasticsearch.xpack.esql.parser.LogicalPlanBuilder.lambda$visitMvExpandCommand$3(LogicalPlanBuilder.java:154)
        at org.elasticsearch.xpack.esql.parser.LogicalPlanBuilder.visitCompositeQuery(LogicalPlanBuilder.java:89)
        at org.elasticsearch.xpack.esql.parser.LogicalPlanBuilder.visitCompositeQuery(LogicalPlanBuilder.java:66)
        at org.elasticsearch.xpack.esql.parser.EsqlBaseParser$CompositeQueryContext.accept(EsqlBaseParser.java:232)
        at org.elasticsearch.xpack.ql.parser.ParserUtils.typedParsing(ParserUtils.java:51)
        at org.elasticsearch.xpack.esql.parser.LogicalPlanBuilder.plan(LogicalPlanBuilder.java:73)
        at org.elasticsearch.xpack.esql.parser.LogicalPlanBuilder.visitSingleStatement(LogicalPlanBuilder.java:82)
        at org.elasticsearch.xpack.esql.parser.LogicalPlanBuilder.visitSingleStatement(LogicalPlanBuilder.java:66)
        at org.elasticsearch.xpack.esql.parser.EsqlBaseParser$SingleStatementContext.accept(EsqlBaseParser.java:169)
```

The problem is that MV_EXPAND tries to pre-calculate the output too early, when the resolution did not happen yet.
x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/parser/StatementParserTests.java
assertThat(alias.child().fold(), is(1));
        field = row.fields().get(1);
        assertThat(field.name(), is("y"));
        assertThat(field, instanceOf(Alias.class));
        alias = (Alias) field;
        assertThat(alias.child().fold(), is("2"));
        field = row.fields().get(2);
        assertThat(field.name(), is("a"));
        assertThat(field, instanceOf(Alias.class));
        alias = (Alias) field;
        assertThat(alias.child().fold(), is(Period.ofDays(2)));
        field = row.fields().get(3);
        assertThat(field.name(), is("b"));
        assertThat(field, instanceOf(Alias.class));
        alias = (Alias) field;
        assertThat(alias.child().fold(), is(Duration.ofHours(4)));
        field = row.fields().get(4);
        assertThat(field.name(), is("c"));
        assertThat(field, instanceOf(Alias.class));
        alias = (Alias) field;
        assertThat(alias.child().fold().getClass(), is(Version.class));
        assertThat(alias.child().fold().toString(), is("1.2.3"));
    }
    public void testWrongIntervalParams() {
        expectError("row x = ?", List.of(new TypedParamValue("date_period", "12")), "Cannot parse [12] to DATE_PERIOD");
        expectError("row x = ?", List.of(new TypedParamValue("time_duration", "12")), "Cannot parse [12] to TIME_DURATION");
        expectError(
            "row x = ?",
            List.of(new TypedParamValue("date_period", "12 months foo")),
            "Cannot parse [12 months foo] to DATE_PERIOD"