langkit/testsuite/tests/python_api/unit_providers/test.lkt

from lexer_example import foo_lexer

@with_lexer(foo_lexer)
grammar foo_grammar {
    @main_rule main_rule <- pick(list*(block) @Termination)
    block <- Block("{" list*(or(ref | def)) "}")
    ref <- Ref(@Identifier("ref") id "." id)
    def <- Def(id)
    id <- Id(@Identifier)
}

struct BlockLocation {
    unit: AnalysisUnit
    ple_root_index: Int
}

@abstract
class FooNode implements Node[FooNode] {
}

class Id: FooNode implements TokenNode {
    @external()
    fun block_location(): BlockLocation

    fun referenced_block(): Block = {
        val loc = node.block_location();
        loc.unit.root.as[ASTList[Block]]?.at(loc.ple_root_index)
    }
}

class Ref: FooNode {
    @parse_field block_name: Id
    @parse_field def_name: Id

    @exported
    fun resolve(): Entity[FooNode] = {
        val block = node.block_name.referenced_block();
        block.children_env.get_first(node.def_name.symbol)
    }
}

class Def: FooNode {
    @parse_field name: Id

    env_spec {
        add_to_env_kv(node.name.symbol, node)
    }
}

@ple_unit_root
class Block: FooNode {
    @parse_field items: ASTList[FooNode]
     env_spec {
         add_env()
     }
}