Doesn't compile on 0.24.2

[andrewzah]

Error:

in lib/db/src/db/query_methods.cr:215: can't infer block return type, try to cast the block body with `as`. See: https://github.com/crystal-lang/crystal/wiki/Compiler-error-messages#cant-infer-block-return-type

      query_all(query, *args) do |rs|
      ^~~~~~~~~

crystal version:

Crystal 0.24.2 (2018-03-19)

LLVM: 6.0.0
Default target: x86_64-pc-linux-gnu

edit: expanded error trace:

in lib/micrate/src/micrate/cli.cr:7: instantiating 'Micrate:Module#up(DB::Database)'

        Micrate.up(db)
                ^~

in lib/micrate/src/micrate.cr:27: instantiating 'dbversion(DB::Database)'

    current = dbversion(db)
              ^~~~~~~~~

in lib/micrate/src/micrate.cr:16: instantiating 'Micrate::DB:Module#get_versions_last_first_order(DB::Database)'

      rows = DB.get_versions_last_first_order(db)
                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~

in lib/micrate/src/micrate/db.cr:30: instantiating 'DB::Database#query_all(String)'

      db.query_all "SELECT version_id, is_applied from micrate_db_version ORDER BY id DESC", as: {Int64, Bool}
         ^~~~~~~~~

in lib/db/src/db/query_methods.cr:215: can't infer block return type, try to cast the block body with `as`. See: https://github.com/crystal-lang/crystal/wiki/Compiler-error-messages#cant-infer-block-return-type

      query_all(query, *args) do |rs|

[bcardiff]

Hi @azah that cast wont work becuase the intention is to return a specific tuple type, not just Type.

Probably there is an issue in the code you are not sharing yet.
Please, reduce the code / show the call for query_all or ask in Gitter / SO.

[andrewzah]

I'm using micrate, which as far as I can tell has this code:

    def self.get_versions_last_first_order(db)
      db.query_all "SELECT version_id, is_applied from micrate_db_version ORDER BY id DESC", as: {Int64, Bool}
    end

[andrewzah]

An expanded error trace:

in lib/micrate/src/micrate/cli.cr:7: instantiating 'Micrate:Module#up(DB::Database)'

        Micrate.up(db)
                ^~

in lib/micrate/src/micrate.cr:27: instantiating 'dbversion(DB::Database)'

    current = dbversion(db)
              ^~~~~~~~~

in lib/micrate/src/micrate.cr:16: instantiating 'Micrate::DB:Module#get_versions_last_first_order(DB::Database)'

      rows = DB.get_versions_last_first_order(db)
                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~

in lib/micrate/src/micrate/db.cr:30: instantiating 'DB::Database#query_all(String)'

      db.query_all "SELECT version_id, is_applied from micrate_db_version ORDER BY id DESC", as: {Int64, Bool}
         ^~~~~~~~~

in lib/db/src/db/query_methods.cr:215: can't infer block return type, try to cast the block body with `as`. See: https://github.com/crystal-lang/crystal/wiki/Compiler-error-messages#cant-infer-block-return-type

      query_all(query, *args) do |rs|

[andrewzah]

query_all calls read which calls internal_read:

   # micrate.cr
    def query_migration_status(migration, db)
      db.query_all "SELECT tstamp, is_applied FROM micrate_db_version WHERE version_id=$1 ORDER BY tstamp DESC LIMIT 1", migration.version, as: {Time, Bool}
    end

   # lib/db/src/db/query_methods.cr
   def query_all(query, *args, as types : Tuple)
      query_all(query, *args) do |rs|
        rs.read(*types)
      end
    end

    # lib/db/src/db/result_set.cr
    def read(*types : Class)
      internal_read(*types)
    end

    private def internal_read(*types : *T) forall T
      {% begin %}
        Tuple.new(
          {% for type in T %}
            read({{type.instance}}),
          {% end %}
        )
      {% end %}
    end

[beta-ziliani]

@andrewzah I assume we can close this one?