Fix inference of accessors on args in let bindings

Fixes #959
coalton-lang · Jun 15, 2023 · f09d9b5 · f09d9b5
1 parent 7819a1f
commit f09d9b5
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Showing 2 changed files with 19 additions and 2 deletions.
diff --git a/src/typechecker/define.lisp b/src/typechecker/define.lisp
@@ -2272,8 +2272,14 @@ Returns (VALUES INFERRED-TYPE NODE SUBSTITUTIONS)")
                     :span (parser:node-source second)
                     :message "second parameter here"))))))
 
-  (let* ((param-tys (loop :for pattern :in (parser:binding-parameters binding)
-                          :collect (tc:make-variable)))
+  (let* ((param-tys (loop :with args := (tc:function-type-arguments expected-type)
+                          :for pattern :in (parser:binding-parameters binding)
+
+                          :if args
+                            :collect (car args)
+                            :and :do (setf args (cdr args))
+                          :else
+                            :collect (tc:make-variable)))
 
          (params (loop :for pattern :in (parser:binding-parameters binding)
                        :for ty :in param-tys

diff --git a/tests/struct-tests.lisp b/tests/struct-tests.lisp
@@ -89,3 +89,14 @@
       (define (f _)
         (let ((g (fn (p) (.x p))))
           (g (Point 1 2))))")))
+
+;; See gh #959
+(deftest test-accessor-on-argument-let-binding ()
+  (check-coalton-types
+   "(define-struct (Wrapper :a)
+     (inner :a))
+
+    (declare f (Wrapper :a -> :a))
+    (define (f x)
+      (let ((y (.inner x)))
+       y))"))