From f30e73fc8028e482868c0ccbb7a9cf7b4a3983c6 Mon Sep 17 00:00:00 2001
From: Sheetal Nandi <shkamat@microsoft.com>
Date: Fri, 5 Oct 2018 15:37:41 -0700
Subject: [PATCH] Report the errors for static incompatibility only if instance
 types are assignable Fixes #26138

---
 src/compiler/checker.ts                       |  7 ++--
 ...taticMismatchBecauseOfPrototype.errors.txt | 19 ++++++++++
 .../staticMismatchBecauseOfPrototype.js       | 36 +++++++++++++++++++
 .../staticMismatchBecauseOfPrototype.symbols  | 26 ++++++++++++++
 .../staticMismatchBecauseOfPrototype.types    | 22 ++++++++++++
 .../staticMismatchBecauseOfPrototype.ts       | 11 ++++++
 6 files changed, 119 insertions(+), 2 deletions(-)
 create mode 100644 tests/baselines/reference/staticMismatchBecauseOfPrototype.errors.txt
 create mode 100644 tests/baselines/reference/staticMismatchBecauseOfPrototype.js
 create mode 100644 tests/baselines/reference/staticMismatchBecauseOfPrototype.symbols
 create mode 100644 tests/baselines/reference/staticMismatchBecauseOfPrototype.types
 create mode 100644 tests/cases/compiler/staticMismatchBecauseOfPrototype.ts

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index ba0b180b71..2126b12894 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -26069,8 +26069,11 @@ namespace ts {
                     if (!checkTypeAssignableTo(typeWithThis, baseWithThis, /*errorNode*/ undefined)) {
                         issueMemberSpecificError(node, typeWithThis, baseWithThis, Diagnostics.Class_0_incorrectly_extends_base_class_1);
                     }
-                    checkTypeAssignableTo(staticType, getTypeWithoutSignatures(staticBaseType), node.name || node,
-                        Diagnostics.Class_static_side_0_incorrectly_extends_base_class_static_side_1);
+                    else {
+                        // Report static side error only when instance type is assignable
+                        checkTypeAssignableTo(staticType, getTypeWithoutSignatures(staticBaseType), node.name || node,
+                            Diagnostics.Class_static_side_0_incorrectly_extends_base_class_static_side_1);
+                    }
                     if (baseConstructorType.flags & TypeFlags.TypeVariable && !isMixinConstructorType(staticType)) {
                         error(node.name || node, Diagnostics.A_mixin_class_must_have_a_constructor_with_a_single_rest_parameter_of_type_any);
                     }
diff --git a/tests/baselines/reference/staticMismatchBecauseOfPrototype.errors.txt b/tests/baselines/reference/staticMismatchBecauseOfPrototype.errors.txt
new file mode 100644
index 0000000000..4976019680
--- /dev/null
+++ b/tests/baselines/reference/staticMismatchBecauseOfPrototype.errors.txt
@@ -0,0 +1,19 @@
+tests/cases/compiler/staticMismatchBecauseOfPrototype.ts(10,5): error TS2416: Property 'n' in type 'B' is not assignable to the same property in base type 'A'.
+  Type 'string' is not assignable to type 'number'.
+
+
+==== tests/cases/compiler/staticMismatchBecauseOfPrototype.ts (1 errors) ====
+    interface A {
+        n: number;
+    }
+    declare var A: {
+        prototype: A;
+        new(): A;
+    };
+    
+    class B extends A {
+        n = "";
+        ~
+!!! error TS2416: Property 'n' in type 'B' is not assignable to the same property in base type 'A'.
+!!! error TS2416:   Type 'string' is not assignable to type 'number'.
+    }
\ No newline at end of file
diff --git a/tests/baselines/reference/staticMismatchBecauseOfPrototype.js b/tests/baselines/reference/staticMismatchBecauseOfPrototype.js
new file mode 100644
index 0000000000..4bc7b24895
--- /dev/null
+++ b/tests/baselines/reference/staticMismatchBecauseOfPrototype.js
@@ -0,0 +1,36 @@
+//// [staticMismatchBecauseOfPrototype.ts]
+interface A {
+    n: number;
+}
+declare var A: {
+    prototype: A;
+    new(): A;
+};
+
+class B extends A {
+    n = "";
+}
+
+//// [staticMismatchBecauseOfPrototype.js]
+var __extends = (this && this.__extends) || (function () {
+    var extendStatics = function (d, b) {
+        extendStatics = Object.setPrototypeOf ||
+            ({ __proto__: [] } instanceof Array && function (d, b) { d.__proto__ = b; }) ||
+            function (d, b) { for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p]; };
+        return extendStatics(d, b);
+    };
+    return function (d, b) {
+        extendStatics(d, b);
+        function __() { this.constructor = d; }
+        d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
+    };
+})();
+var B = /** @class */ (function (_super) {
+    __extends(B, _super);
+    function B() {
+        var _this = _super !== null && _super.apply(this, arguments) || this;
+        _this.n = "";
+        return _this;
+    }
+    return B;
+}(A));
diff --git a/tests/baselines/reference/staticMismatchBecauseOfPrototype.symbols b/tests/baselines/reference/staticMismatchBecauseOfPrototype.symbols
new file mode 100644
index 0000000000..98abd4b9e1
--- /dev/null
+++ b/tests/baselines/reference/staticMismatchBecauseOfPrototype.symbols
@@ -0,0 +1,26 @@
+=== tests/cases/compiler/staticMismatchBecauseOfPrototype.ts ===
+interface A {
+>A : Symbol(A, Decl(staticMismatchBecauseOfPrototype.ts, 0, 0), Decl(staticMismatchBecauseOfPrototype.ts, 3, 11))
+
+    n: number;
+>n : Symbol(A.n, Decl(staticMismatchBecauseOfPrototype.ts, 0, 13))
+}
+declare var A: {
+>A : Symbol(A, Decl(staticMismatchBecauseOfPrototype.ts, 0, 0), Decl(staticMismatchBecauseOfPrototype.ts, 3, 11))
+
+    prototype: A;
+>prototype : Symbol(prototype, Decl(staticMismatchBecauseOfPrototype.ts, 3, 16))
+>A : Symbol(A, Decl(staticMismatchBecauseOfPrototype.ts, 0, 0), Decl(staticMismatchBecauseOfPrototype.ts, 3, 11))
+
+    new(): A;
+>A : Symbol(A, Decl(staticMismatchBecauseOfPrototype.ts, 0, 0), Decl(staticMismatchBecauseOfPrototype.ts, 3, 11))
+
+};
+
+class B extends A {
+>B : Symbol(B, Decl(staticMismatchBecauseOfPrototype.ts, 6, 2))
+>A : Symbol(A, Decl(staticMismatchBecauseOfPrototype.ts, 0, 0), Decl(staticMismatchBecauseOfPrototype.ts, 3, 11))
+
+    n = "";
+>n : Symbol(B.n, Decl(staticMismatchBecauseOfPrototype.ts, 8, 19))
+}
diff --git a/tests/baselines/reference/staticMismatchBecauseOfPrototype.types b/tests/baselines/reference/staticMismatchBecauseOfPrototype.types
new file mode 100644
index 0000000000..d55c86b3fc
--- /dev/null
+++ b/tests/baselines/reference/staticMismatchBecauseOfPrototype.types
@@ -0,0 +1,22 @@
+=== tests/cases/compiler/staticMismatchBecauseOfPrototype.ts ===
+interface A {
+    n: number;
+>n : number
+}
+declare var A: {
+>A : { new (): A; prototype: A; }
+
+    prototype: A;
+>prototype : A
+
+    new(): A;
+};
+
+class B extends A {
+>B : B
+>A : A
+
+    n = "";
+>n : string
+>"" : ""
+}
diff --git a/tests/cases/compiler/staticMismatchBecauseOfPrototype.ts b/tests/cases/compiler/staticMismatchBecauseOfPrototype.ts
new file mode 100644
index 0000000000..24d50f1951
--- /dev/null
+++ b/tests/cases/compiler/staticMismatchBecauseOfPrototype.ts
@@ -0,0 +1,11 @@
+interface A {
+    n: number;
+}
+declare var A: {
+    prototype: A;
+    new(): A;
+};
+
+class B extends A {
+    n = "";
+}
\ No newline at end of file