fix: Normalize unions

Closes #571.
TypeStrong · Dec 27, 2020 · 9f8375d · 9f8375d
1 parent 33c2bc6
commit 9f8375d
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Showing 3 changed files with 156 additions and 86 deletions.
diff --git a/src/lib/models/types/union.ts b/src/lib/models/types/union.ts
@@ -1,4 +1,6 @@
 import { Type } from "./abstract";
+import { IntrinsicType } from "./intrinsic";
+import { LiteralType } from "./literal";
 
 /**
  * Represents an union type.
@@ -26,6 +28,7 @@ export class UnionType extends Type {
     constructor(types: Type[]) {
         super();
         this.types = types;
+        this.normalize();
     }
 
     /**
@@ -61,4 +64,22 @@ export class UnionType extends Type {
 
         return names.join(" | ");
     }
+
+    private normalize() {
+        const trueIndex = this.types.findIndex((t) =>
+            t.equals(new LiteralType(true))
+        );
+        const falseIndex = this.types.findIndex((t) =>
+            t.equals(new LiteralType(false))
+        );
+
+        if (trueIndex !== -1 && falseIndex !== -1) {
+            this.types.splice(Math.max(trueIndex, falseIndex), 1);
+            this.types.splice(
+                Math.min(trueIndex, falseIndex),
+                1,
+                new IntrinsicType("boolean")
+            );
+        }
+    }
 }
diff --git a/src/test/converter/function/function.ts b/src/test/converter/function/function.ts
@@ -198,3 +198,9 @@ export const all: {
     <T>(fn: (item: T) => boolean, iterator: Iterable<T>): boolean;
     <T>(fn: (item: T) => boolean): (iterator: Iterable<T>) => boolean;
 } = () => false as any;
+
+export function boolOrUndef(x: number) {
+    if (x < 5) return true;
+    if (x > 20) return false;
+    return undefined;
+}