From a949d974c329173dd59f5371d261c87f0e574d86 Mon Sep 17 00:00:00 2001
From: Oliver Joseph Ash <oliverjash@gmail.com>
Date: Wed, 16 Oct 2019 11:54:03 +0100
Subject: [PATCH] fix: use `unknown` type for errors

---
 spec-dtslint/Observable-spec.ts   | 8 ++++++++
 spec/observables/dom/ajax-spec.ts | 8 ++++++--
 src/internal/types.ts             | 8 ++++----
 3 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/spec-dtslint/Observable-spec.ts b/spec-dtslint/Observable-spec.ts
index ee7c1b1053..aa8790d72c 100644
--- a/spec-dtslint/Observable-spec.ts
+++ b/spec-dtslint/Observable-spec.ts
@@ -126,4 +126,12 @@ describe('pipe', () => {
     const customOperator = () => <T>(a: Observable<T>) => a;
     const o = of('foo').pipe(customOperator()); // $ExpectType Observable<string>
   });
+
+  it('should not make assumptions about the error type', () => {
+    of('foo').subscribe({
+      error: error => {
+        error.name; // $ExpectError
+      }
+    });
+  });
 });
diff --git a/spec/observables/dom/ajax-spec.ts b/spec/observables/dom/ajax-spec.ts
index fcd8e1cfeb..4b57fbfd8f 100644
--- a/spec/observables/dom/ajax-spec.ts
+++ b/spec/observables/dom/ajax-spec.ts
@@ -974,8 +974,12 @@ describe('ajax', () => {
     ajax(ajaxRequest)
       .subscribe({
         error(err) {
-          expect(err.name).to.equal('AjaxTimeoutError');
-          done();
+          if (err instanceof AjaxTimeoutError) {
+            expect(err.name).to.equal('AjaxTimeoutError');
+            done();
+          } else {
+            throw new Error('expected an AjaxTimeoutError');
+          }
         }
       });
 
diff --git a/src/internal/types.ts b/src/internal/types.ts
index a014cc1634..782dae5c6f 100644
--- a/src/internal/types.ts
+++ b/src/internal/types.ts
@@ -61,21 +61,21 @@ export type InteropObservable<T> = { [Symbol.observable]: () => Subscribable<T>;
 export interface NextObserver<T> {
   closed?: boolean;
   next: (value: T) => void;
-  error?: (err: any) => void;
+  error?: (err: unknown) => void;
   complete?: () => void;
 }
 
 export interface ErrorObserver<T> {
   closed?: boolean;
   next?: (value: T) => void;
-  error: (err: any) => void;
+  error: (err: unknown) => void;
   complete?: () => void;
 }
 
 export interface CompletionObserver<T> {
   closed?: boolean;
   next?: (value: T) => void;
-  error?: (err: any) => void;
+  error?: (err: unknown) => void;
   complete: () => void;
 }
 
@@ -84,7 +84,7 @@ export type PartialObserver<T> = NextObserver<T> | ErrorObserver<T> | Completion
 export interface Observer<T> {
   closed?: boolean;
   next: (value: T) => void;
-  error: (err: any) => void;
+  error: (err: unknown) => void;
   complete: () => void;
 }