[bug-fix] no-invalid-this / ignore functions w "this" param

src/rules/noInvalidThisRule.ts

@@ -15,9 +15,9 @@
  * limitations under the License.
  */
 
+import { isThisParameter } from "tsutils";
 import * as ts from "typescript";
-
-import * as Lint from "../index";
+import * as Lint from "..";
 
 const OPTION_FUNCTION_IN_METHOD = "check-function-in-method";
 const DEPRECATED_OPTION_FUNCTION_IN_METHOD = "no-this-in-function-in-method";
@@ -47,7 +47,7 @@ export class Rule extends Lint.Rules.AbstractRule {
     };
     /* tslint:enable:object-literal-sort-keys */
 
-    public static FAILURE_STRING_OUTSIDE = "the \"this\" keyword is disallowed outside of a class body" ;
+    public static FAILURE_STRING_OUTSIDE = "the \"this\" keyword is disallowed outside of a class body";
     public static FAILURE_STRING_INSIDE = "the \"this\" keyword is disallowed in function bodies inside class methods, " +
         "use arrow functions instead";
     public apply(sourceFile: ts.SourceFile): Lint.RuleFailure[] {
@@ -76,6 +76,9 @@ function walk(ctx: Lint.WalkContext<boolean>): void {
 
             case ts.SyntaxKind.FunctionDeclaration:
             case ts.SyntaxKind.FunctionExpression:
+                if ((node as ts.FunctionLikeDeclaration).parameters.some(isThisParameter)) {
+                    return;
+                }
                 if (inClass) {
                     inFunctionInClass = true;
                     ts.forEachChild(node, cb);

test/rules/no-invalid-this/enabled/test.ts.lint

@@ -1,3 +1,21 @@
+export function f<T>(this: Observable<T>): Observable<T> {
+    const nestedFunction = function(this) => {
+        console.log(this)
+    }
+    return this.map(i=>i);
+}
+
+class ContextualThisClass {
+    private someMethod(): void {
+        let nestedFunction: (this: number[]) => number[] = function(this) {
+            [3,4].forEach(function(nr){
+                console.log(this);
+            });
+            return this.map(i=>i);
+        };
+    }
+}
+
 function foo(x: number) {
     console.log(this.x);
                 ~~~~                      [the "this" keyword is disallowed outside of a class body]