Polish: make isIndexableCodec more strict

CHANGELOG.md

@@ -14,6 +14,11 @@
 **Note**: Gaps between patch versions are faulty/broken releases. **Note**: A feature tagged as Experimental is in a
 high state of flux, you're at risk of it changing without notice.
 
+# 1.6.2
+
+- **Polish**
+  - make `isIndexableCodec` more strict (@gcanti)
+
 # 1.6.1
 
 - **Bug Fix**

package.json

@@ -1,6 +1,6 @@
 {
   "name": "io-ts",
-  "version": "1.6.1",
+  "version": "1.6.2",
   "description": "TypeScript compatible runtime type system for IO validation",
   "files": [
     "lib"

src/index.ts

@@ -1601,12 +1601,11 @@ const getCodecIndexRecord = (codec: Mixed, override: Mixed = codec): IndexRecord
 
 const isIndexableCodec = (codec: Mixed): boolean => {
   return (
-    isInterfaceCodec(codec) ||
-    isExactCodec(codec) ||
-    isIntersectionCodec(codec) ||
-    isUnionCodec(codec) ||
-    isStrictCodec(codec) ||
-    isRefinementCodec(codec) ||
+    ((isInterfaceCodec(codec) || isStrictCodec(codec)) &&
+      Object.keys(codec.props).some(key => isLiteralCodec(codec.props[key]))) ||
+    ((isExactCodec(codec) || isRefinementCodec(codec)) && isIndexableCodec(codec.type)) ||
+    (isIntersectionCodec(codec) && codec.types.some(isIndexableCodec)) ||
+    (isUnionCodec(codec) && codec.types.every(isIndexableCodec)) ||
     isRecursiveCodec(codec)
   )
 }

test/taggedUnion.ts

@@ -297,4 +297,24 @@ describe('getIndexRecord', () => {
       kind: [['C2', C], ['D2', D]]
     })
   })
+
+  it('should handle recursive types defined with a union containing a non indexable codec', () => {
+    // non indexable codec
+    const A = t.type({
+      a: t.string
+    })
+
+    type A = t.TypeOf<typeof A>
+
+    interface B {
+      modules: A | B
+    }
+
+    const B = t.recursion<B>('B', self =>
+      t.type({
+        modules: t.union([A, self])
+      })
+    )
+    assert.deepEqual(t.getIndexRecord([B]), {})
+  })
 })