Improve type errors

[Sciencei]

Improves the type errors in squeal, mostly using custom type errors. All changes are described in the release notes as well.

Improves the type errors produced by Has/HasErr.

Examples:

Lookup failed

exe/Example.hs:112:11-41: error:
    • Could not find table, view, typedef, index, function, or procedure (SchemumType) named "sers"
      in schema (SchemaType):
        Tables:
          '["emails", "users"]

      *Raw schema (SchemaType)*:
      '[ '("users",
           'Table
             ('["pk_users" ::: 'PrimaryKey '["id"]]
              :=> '["id" ::: ('Def :=> 'NotNull 'PGint4),
                    "name" ::: ('NoDef :=> 'NotNull 'PGtext),
                    "vec" ::: ('NoDef :=> 'NotNull ('PGvararray ('Null 'PGint2)))])),
         "emails"
         ::: 'Table
               ('["pk_emails" ::: 'PrimaryKey '["id"],
                  "fk_user_id" ::: 'ForeignKey '["user_id"] "user" "users" '["id"]]
                :=> '["id" ::: ('Def :=> 'NotNull 'PGint4),
                      "user_id" ::: ('NoDef :=> 'NotNull 'PGint4),
                      "email" ::: ('NoDef :=> 'Null 'PGtext)])]

    • In the first argument of ‘(&)’, namely
        ‘table ((#user ! #sers) `as` #u)’
      In the first argument of ‘from’, namely
        ‘(table ((#user ! #sers) `as` #u)
            & innerJoin
                (table ((#user ! #emails) `as` #e)) (#u ! #id .== #e ! #user_id))’
      In the second argument of ‘select_’, namely
        ‘(from
            (table ((#user ! #sers) `as` #u)
               & innerJoin
                   (table ((#user ! #emails) `as` #e)) (#u ! #id .== #e ! #user_id)))’
    |
112 |   ( from (table ((#user ! #sers) `as` #u)
    |           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
exe/Example.hs:(106,15)-(107,92): error:
    • Could not find schema (SchemaType) named "use"
      in database (SchemasType):
        '["org", "public", "user"]

      *Raw database (SchemasType)*:
      '[ '("public", PublicSchema), "user" ::: UserSchema,
         "org" ::: OrgSchema]

    • In the expression:
        insertInto_
          (#use ! #emails)
          (Values_
             (Default `as` #id
                :* Set (param @1) `as` #user_id :* Set (param @2) `as` #email))
      In an equation for ‘insertEmail’:
          insertEmail
            = insertInto_
                (#use ! #emails)
                (Values_
                   (Default `as` #id
                      :* Set (param @1) `as` #user_id :* Set (param @2) `as` #email))
    |
106 | insertEmail = insertInto_ (#use ! #emails)
    |               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^...

Lookup succeeded, but types don't match

exe/Example.hs:111:4-12: error:
    • Type mismatch when looking up column (NullType) named "vec"
      in row (RowType):
      '[ '("id", 'NotNull 'PGint4), "name" ::: 'NotNull 'PGtext,
         "vec" ::: 'NotNull ('PGvararray ('Null 'PGint2))]

      Expected: 'NotNull 'PGtext
      But found: 'NotNull ('PGvararray ('Null 'PGint2))

    • In the first argument of ‘as’, namely ‘#u ! #vec’
      In the first argument of ‘(:*)’, namely ‘#u ! #vec `as` #userName’
      In the first argument of ‘select_’, namely
        ‘(#u ! #vec `as` #userName
            :* #e ! #email `as` #userEmail :* #u ! #vec `as` #userVec)’
    |
111 |   (#u ! #vec `as` #userName :* #e ! #email `as` #userEmail :* #u ! #vec `as` #userVec)
    |    ^^^^^^^^^

Ambiguous types

No custom error here, but the error complains about Has instead of HasErr

exe/Example.hs:103:16-37: error:
    • Ambiguous type variables ‘constraints0’,
                               ‘constraint0’ arising from a use of ‘OnConstraint’
      prevents the constraint ‘(Has
                                  "pk_users" constraints0 constraint0)’ from being solved.
      Probable fix: use a type annotation to specify what ‘constraints0’,
                                                          ‘constraint0’ should be.
      These potential instances exist:
        three instances involving out-of-scope types
        (use -fprint-potential-instances to see them all)
    • In the first argument of ‘OnConflict’, namely
        ‘(OnConstraint #pk_users)’
      In the third argument of ‘insertInto’, namely
        ‘(OnConflict (OnConstraint #pk_users) DoNothing)’
      In the expression:
        insertInto
          (#user ! #users)
          (Values_
             (Default `as` #id
                :* Set (param @1) `as` #name :* Set (param @2) `as` #vec))
          (OnConflict (OnConstraint #pk_users) DoNothing)
          (Returning_ (#id `as` #fromOnly))
    |
103 |   (OnConflict (OnConstraint #pk_users) DoNothing) (Returning_ (#id `as` #fromOnly))
    |                ^^^^^^^^^^^^^^^^^^^^^^

Improves the type errors produced by HasParameter.

This added a HasParameter' typeclass in the same vein as HasErr, but it should be hidden from errors in the same way HasErr now is.

Examples:

Looking up index 0

exe/Example.hs:118:18-25: error:
    • Tried to get the param at index 0, but params are 1-indexed
    • In the first argument of ‘Set’, namely ‘(param @0)’
      In the first argument of ‘as’, namely ‘Set (param @0)’
      In the first argument of ‘(:*)’, namely ‘Set (param @0) `as` #id’
    |
118 |   (Values_ (Set (param @0) `as` #id :* setUser))
    |                  ^^^^^^^^

Looking up an out-of-bounds parameter

exe/Example.hs:118:18-25: error:
    • Index 4 is out of bounds in 1-indexed parameter list:
      '[ 'NotNull 'PGint4, 'NotNull 'PGtext,
         'NotNull ('PGvararray ('Null 'PGint2))]
    • In the first argument of ‘Set’, namely ‘(param @4)’
      In the first argument of ‘as’, namely ‘Set (param @4)’
      In the first argument of ‘(:*)’, namely ‘Set (param @4) `as` #id’
    |
118 |   (Values_ (Set (param @4) `as` #id :* setUser))
    |                  ^^^^^^^^

Type mismatch when doing lookup

exe/Example.hs:118:18: error:
    • Type mismatch when looking up param at index 2
      in 1-indexed parameter list:
        '[ 'NotNull 'PGint4, 'NotNull 'PGtext,
           'NotNull ('PGvararray ('Null 'PGint2))]

      Expected: 'NotNull 'PGtext
      But found: 'NotNull 'PGint4

    • In the first argument of ‘Set’, namely ‘(param @2)’
      In the first argument of ‘as’, namely ‘Set (param @2)’
      In the first argument of ‘(:*)’, namely ‘Set (param @2) `as` #id’
    |
118 |   (Values_ (Set (param @2) `as` #id :* setUser))
    |                  ^^^^^^^^

Gives a nice custom error when trying to use aggregates with an ungrouped expression

exe/Example.hs:118:4: error:
    • Cannot use aggregate functions to construct an Ungrouped Expression. Add a 'groupBy' to your TableExpression. If you want to aggregate across the entire result set, use 'groupBy Nil'.
    • In the first argument of ‘as’, namely ‘countStar’
      In the first argument of ‘(:*)’, namely ‘countStar `as` #count’
      In the first argument of ‘select_’, namely
        ‘(countStar `as` #count :* Nil)’
    |
118 |   (countStar `as` #count :* Nil)
    |    ^^^^^^^^^

[echatav]

Looks great! Thanks for keeping Has intact.