Add `define-type-alias` #1294

YarinHeffes · 2024-10-08T23:39:18Z

This is an implementation of type aliases, including:

simple aliases:

(define-type-alias Coordinate Integer)

aliases of aliases:

(define-type-alias Point (Tuple Coordinate Coordinate))
(define-type-alias Translation (Point -> Point))

and readable printing in error messages.

[Point := (Tuple [Coordinate := Integer] [Coordinate := Integer])]

The implementation also supports parametric type aliases

(define-type-alias (UnaryOperator :a) (:a -> :a))
(define-type-alias UnaryIntegerOperator (UnaryOperator Integer))
---
[UnaryIntegerOperator := (UnaryOperator Integer) := (Integer -> Integer)]

Currently, since the does not change types except by substituting type-variables,

(define x (the Coordinate (the Integer 5)))

will compile, but it will not store the alias Coordinate for the variable x, and it will not display in error messages.

The functions describe-type-alias and describe-type-of are implemented to display the definition of a type alias and the aliases of a defined symbol, respectively.

stylewarning · 2024-10-10T19:23:56Z

I think this PR should be blocked on a complete and tested implementation. I am sympathetic to incomplete library additions, but language features need to be complete and bullet-proof.

Izaakwltn · 2024-10-16T21:10:56Z

I think it would be a good idea to add some documentation in these files:

docs/intro-to-coalton.md
docs/coalton-documentation-guide.md
maybe in docs/coalton-lisp-interop.md, if there are any promises (or lack thereof) about lisp alias behavior.

stylewarning

Just some initial thoughts. Not a full review.

docs/coalton-documentation-guide.md

src/faux-macros.lisp

stylewarning · 2024-10-17T05:21:36Z

docs/intro-to-coalton.md

+COALTON-USER> (type-of 'shifted-coordinate)
+(TUPLE INTEGER INTEGER)
+
+COALTON-USER> (describe-type-of 'shifted-coordinate)


I think these functions and their output may need some workshopping.

Do you have any feedback as far as what is good/bad about them?

src/parser/toplevel.lisp

src/typechecker/base.lisp

stylewarning · 2024-10-17T05:30:17Z

@YarinHeffes Can you update the PR description with an up-to-date account of the PR?

stylewarning · 2024-10-17T23:12:17Z

src/parser/toplevel.lisp

+                            "remove unnecessary parentheses")))
+
+       ;; (define-type-alias (name type-variables+) ...)
+       (loop :for vars := (cst:rest (cst:second form)) :then (cst:rest vars)


check that the tyvars are unique

This takes place during the type checking phase, similar to define-struct and define-type

stylewarning · 2024-10-17T23:17:48Z

src/typechecker/define-type.lisp

+  (let* ((defined-variables (mapcar #'parser:keyword-src-name (parser:type-definition-vars parsed-type)))
+         (used-variables (mapcar #'tc:tyvar-id (tc:type-variables aliased-type)))
+         (unused-variables (loop :for tyvar :in defined-variables
+                                 :when (not (member (tc:tyvar-id (partial-type-env-lookup-var partial-env tyvar parsed-type))


slightly shorted code: when not => unless

addressed in 8619ceb

stylewarning · 2024-10-17T23:22:22Z

src/typechecker/define-type.lisp

+                (tc-note parsed-type "Type alias ~S defines unused type variable~P ~{:~A~^ ~}"
+                         (parser:identifier-src-name (parser:type-definition-name parsed-type))
+                         number-of-unused-variables
+                         (mapcar (lambda (str) (subseq str 0  (- (length str) (1+ (position #\- (reverse str))))))


(position a b :from-end t)

addressed in 8619ceb

stylewarning · 2024-10-17T23:25:27Z

src/typechecker/define-type.lisp

@@ -420,6 +465,12 @@
                                                 `(member ,@(mapcar #'tc:constructor-entry-compressed-repr ctors)))
                                                (t
                                                 name))
+                                :aliased-type (let ((parser-aliased-type
+                                                      (parser:type-definition-aliased-type type)))
+                                                (when parser-aliased-type


prefer if if the value is load-bearing

addressed in 8619ceb

stylewarning · 2024-10-17T23:31:19Z

src/typechecker/predicate.lisp

@@ -69,6 +70,12 @@
  (predicates (util:required 'predicates) :type ty-predicate-list :read-only t)
  (type       (util:required 'type)       :type ty                :read-only t))

+(defun qualified-ty= (qualified-ty1 qualified-ty2)
+  (and (equalp (qualified-ty-predicates qualified-ty1)


what if the predicates have different orders? is that possible?

I would need to look more into this. However, we were previously using equalp for equality, so this change should not break anything/change any pre-existing behavior.

stylewarning · 2024-10-17T23:35:44Z

src/typechecker/types.lisp

@@ -71,7 +74,8 @@
 ;;; Types
 ;;;

-(defstruct (ty (:constructor nil)))
+(defstruct (ty (:constructor nil))
+  (alias nil :type (or null ty-list) :read-only nil))


Describe in a comment what this field is and when it shoes up. Give an example.

maybe a comment that this could be a weak hash table

addressed in 8619ceb

stylewarning · 2024-10-17T23:58:09Z

src/typechecker/types.lisp

+            (tgen-id type2)))
+
+  (:method (type1 type2)
+    (declare (ignore type1)


ignore can have multiple entries: (declare (ignore a b))

addressed in 8619ceb

YarinHeffes and others added 6 commits October 7, 2024 16:39

added basic define-alias toplevel form

758cf3d

fixed alias substitution for constructors and struct-fields

a125e4a

added alias tests

074488b

improved alias error messages

688322c

removed with-aliases-from

287f089

Merge branch 'coalton-lang:main' into type-alias

77a2443

YarinHeffes requested review from jbouwman and eliaslfox October 8, 2024 23:39

YarinHeffes mentioned this pull request Oct 8, 2024

Add Type Aliases #912

Open

alias coalton-release fix

e05bd8a

YarinHeffes marked this pull request as draft October 10, 2024 20:12

YarinHeffes added 4 commits October 16, 2024 11:38

added parametrized type aliases

db74f65

added tests for parametrized type aliases

ffbef6e

added describe-alias

f252499

added define-alias.txt tests

9dda5c2

YarinHeffes added 3 commits October 16, 2024 14:25

add tutorial documentation for type aliases

314ff0b

added type alias documentation guide

fde68b5

Merge branch 'main' into type-alias

c9ba647

YarinHeffes marked this pull request as ready for review October 16, 2024 21:58

stylewarning requested changes Oct 17, 2024

View reviewed changes

YarinHeffes added 4 commits October 17, 2024 09:45

removed empty line

5851da6

changed :nil to nil

ff0e7f7

added documentation to *pprint-aliases*

9b3beda

changed define-alias -> define-type-alias

57366b7

YarinHeffes changed the title ~~adding define-alias~~ adding define-type-alias Oct 17, 2024

YarinHeffes changed the title ~~adding define-type-alias~~ Add define-type-alias Oct 17, 2024

Improved error message for unused type alias arguments

1aba695

typo fix

e6784b8

stylewarning requested changes Oct 18, 2024

View reviewed changes

minor fixes

8619ceb

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Add `define-type-alias` #1294

Add `define-type-alias` #1294

YarinHeffes commented Oct 8, 2024 •

edited

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YarinHeffes Nov 19, 2024

Add define-type-alias #1294

Are you sure you want to change the base?

Add define-type-alias #1294

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YarinHeffes commented Oct 8, 2024 • edited Loading

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Add `define-type-alias` #1294

Add `define-type-alias` #1294

YarinHeffes commented Oct 8, 2024 •

edited

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