fix(eslint-plugin): [unbound-method] Work around class prototype bug

packages/eslint-plugin/src/rules/unbound-method.ts

@@ -74,6 +74,10 @@ export default util.createRule<Options, MessageIds>({
 
 function isDangerousMethod(symbol: ts.Symbol, ignoreStatic: boolean) {
   const { valueDeclaration } = symbol;
+  if (!valueDeclaration) {
+    // working around https://github.com/microsoft/TypeScript/issues/31294
+    return false;
+  }
 
   switch (valueDeclaration.kind) {
     case ts.SyntaxKind.MethodDeclaration:

packages/eslint-plugin/tests/rules/unbound-method.test.ts

@@ -97,7 +97,7 @@ instane.boundStatic && 0;
 
 ContainsMethods.boundStatic ? 1 : 0;
 ContainsMethods.unboundStatic ? 1 : 0;
-`,
+    `,
     `interface RecordA {
   readonly type: "A"
   readonly a: {}
@@ -111,7 +111,20 @@ type AnyRecord = RecordA | RecordB
 function test(obj: AnyRecord) {
   switch (obj.type) {
   }
-}`,
+}
+    `,
+    // https://github.com/typescript-eslint/typescript-eslint/issues/496
+    `
+class CommunicationError {
+	constructor() {
+    const x = CommunicationError.prototype;
+	}
+}
+    `,
+    `
+class CommunicationError {}
+const x = CommunicationError.prototype;
+    `,
   ],
   invalid: [
     {
@@ -283,5 +296,20 @@ ContainsMethods.unboundStatic;
         },
       ],
     },
+    // https://github.com/typescript-eslint/typescript-eslint/issues/496
+    {
+      code: `
+class CommunicationError {
+  foo() {}
+}
+const x = CommunicationError.prototype.foo;
+      `,
+      errors: [
+        {
+          line: 5,
+          messageId: 'unbound',
+        },
+      ],
+    },
   ],
 });