When generalizing a union type of function types, generalize their ou…

…tput types.

CHANGELOG.md

@@ -10,10 +10,11 @@ Dates are in `YYYY-MM-DD` format and versions are in [semantic versioning](http:
 -   Better tab symbol to clarify keyboard shortcut and whitespace meaning.
 -   Improved contrast of delimiters and borders in dark mode.
 -   Correct typos in tutorial.
+-   Ensured type errors when a structure definition is given instead of a structure value.
+-   When generalizing a union type of function types, generalize their output types.
 -   [#503](https://github.com/wordplaydev/wordplay/issues/503). Prevent infinite loops in parser.
 -   [#504](https://github.com/wordplaydev/wordplay/issues/504). Account for non-fixed-width characters in caret positioning.
 -   [#488](https://github.com/wordplaydev/wordplay/issues/488). Added animations off indicator on stage.
--   Ensured type errors when a structure definition is given instead of a structure value.
 -   [#500](https://github.com/wordplaydev/wordplay/issues/500). Improved explanation when there's a space between an evaluation's name and inputs.
 
 ## 0.10.1 2024-06-22

src/nodes/FunctionType.ts

@@ -134,7 +134,12 @@ export default class FunctionType extends Type {
             const outputToCheck = type.output;
 
             if (!(outputToCheck instanceof Type)) return false;
-            if (!this.output.accepts(outputToCheck, context)) return false;
+            if (
+                !this.output
+                    .generalize(context)
+                    .accepts(outputToCheck.generalize(context), context)
+            )
+                return false;
             // If this function takes fewer than the number of inputs that the given function expects,
             // then the given function will not function correctly. But it is okay if the given
             // function takes fewer inputs then this function, since it just means it's ignoring some of the inputs.