fix(36883): disallow this parameter in set/get accessors

Author: a-tarasyuk

src/compiler/checker.ts

@@ -28545,6 +28545,9 @@ namespace ts {
                 if (func.kind === SyntaxKind.ArrowFunction) {
                     error(node, Diagnostics.An_arrow_function_cannot_have_a_this_parameter);
                 }
+                if (func.kind === SyntaxKind.GetAccessor || func.kind === SyntaxKind.SetAccessor) {
+                    error(node, Diagnostics.get_and_set_accessors_cannot_declare_this_parameters);
+                }
             }
 
             // Only check rest parameter type if it's not a binding pattern. Since binding patterns are

src/compiler/diagnosticMessages.json

@@ -2891,6 +2891,10 @@
         "category": "Error",
         "code": 2783
     },
+    "'get' and 'set' accessors cannot declare 'this' parameters.": {
+        "category": "Error",
+        "code": 2784
+    },
 
     "Import declaration '{0}' is using private name '{1}'.": {
         "category": "Error",

tests/baselines/reference/thisTypeInAccessors.errors.txt

@@ -0,0 +1,63 @@
+tests/cases/conformance/types/thisType/thisTypeInAccessors.ts(8,11): error TS2784: 'get' and 'set' accessors cannot declare 'this' parameters.
+tests/cases/conformance/types/thisType/thisTypeInAccessors.ts(9,11): error TS2784: 'get' and 'set' accessors cannot declare 'this' parameters.
+tests/cases/conformance/types/thisType/thisTypeInAccessors.ts(13,11): error TS2784: 'get' and 'set' accessors cannot declare 'this' parameters.
+tests/cases/conformance/types/thisType/thisTypeInAccessors.ts(19,11): error TS2784: 'get' and 'set' accessors cannot declare 'this' parameters.
+tests/cases/conformance/types/thisType/thisTypeInAccessors.ts(23,11): error TS2784: 'get' and 'set' accessors cannot declare 'this' parameters.
+tests/cases/conformance/types/thisType/thisTypeInAccessors.ts(24,11): error TS2784: 'get' and 'set' accessors cannot declare 'this' parameters.
+tests/cases/conformance/types/thisType/thisTypeInAccessors.ts(29,11): error TS2784: 'get' and 'set' accessors cannot declare 'this' parameters.
+tests/cases/conformance/types/thisType/thisTypeInAccessors.ts(30,11): error TS2784: 'get' and 'set' accessors cannot declare 'this' parameters.
+
+
+==== tests/cases/conformance/types/thisType/thisTypeInAccessors.ts (8 errors) ====
+    interface Foo {
+        n: number;
+        x: number;
+    }
+    
+    const explicit = {
+        n: 12,
+        get x(this: Foo): number { return this.n; },
+              ~~~~~~~~~
+!!! error TS2784: 'get' and 'set' accessors cannot declare 'this' parameters.
+        set x(this: Foo, n: number) { this.n = n; }
+              ~~~~~~~~~
+!!! error TS2784: 'get' and 'set' accessors cannot declare 'this' parameters.
+    }
+    const copiedFromGetter = {
+        n: 14,
+        get x(this: Foo): number { return this.n; },
+              ~~~~~~~~~
+!!! error TS2784: 'get' and 'set' accessors cannot declare 'this' parameters.
+        set x(n) { this.n = n; }
+    }
+    const copiedFromSetter = {
+        n: 15,
+        get x() { return this.n },
+        set x(this: Foo, n: number) { this.n = n; }
+              ~~~~~~~~~
+!!! error TS2784: 'get' and 'set' accessors cannot declare 'this' parameters.
+    }
+    const copiedFromGetterUnannotated = {
+        n: 16,
+        get x(this: Foo) { return this.n },
+              ~~~~~~~~~
+!!! error TS2784: 'get' and 'set' accessors cannot declare 'this' parameters.
+        set x(this, n) { this.n = n; }
+              ~~~~
+!!! error TS2784: 'get' and 'set' accessors cannot declare 'this' parameters.
+    }
+    
+    class Explicit {
+        n = 17;
+        get x(this: Foo): number { return this.n; }
+              ~~~~~~~~~
+!!! error TS2784: 'get' and 'set' accessors cannot declare 'this' parameters.
+        set x(this: Foo, n: number) { this.n = n; }
+              ~~~~~~~~~
+!!! error TS2784: 'get' and 'set' accessors cannot declare 'this' parameters.
+    }
+    class Contextual {
+        n = 21;
+        get x() { return this.n } // inside a class, so already correct
+    }
+    

tests/baselines/reference/thisTypeInAccessorsNegative.errors.txt

@@ -1,8 +1,10 @@
 tests/cases/conformance/types/thisType/thisTypeInAccessorsNegative.ts(10,9): error TS2682: 'get' and 'set' accessor must have the same 'this' type.
+tests/cases/conformance/types/thisType/thisTypeInAccessorsNegative.ts(10,11): error TS2784: 'get' and 'set' accessors cannot declare 'this' parameters.
 tests/cases/conformance/types/thisType/thisTypeInAccessorsNegative.ts(11,9): error TS2682: 'get' and 'set' accessor must have the same 'this' type.
+tests/cases/conformance/types/thisType/thisTypeInAccessorsNegative.ts(11,11): error TS2784: 'get' and 'set' accessors cannot declare 'this' parameters.
 
 
-==== tests/cases/conformance/types/thisType/thisTypeInAccessorsNegative.ts (2 errors) ====
+==== tests/cases/conformance/types/thisType/thisTypeInAccessorsNegative.ts (4 errors) ====
     interface Foo {
         n: number;
         x: number;
@@ -15,9 +17,13 @@ tests/cases/conformance/types/thisType/thisTypeInAccessorsNegative.ts(11,9): err
         get x(this: Foo) { return this.n; },
             ~
 !!! error TS2682: 'get' and 'set' accessor must have the same 'this' type.
+              ~~~~~~~~~
+!!! error TS2784: 'get' and 'set' accessors cannot declare 'this' parameters.
         set x(this: Bar, n) { this.wrong = "method"; }
             ~
 !!! error TS2682: 'get' and 'set' accessor must have the same 'this' type.
+              ~~~~~~~~~
+!!! error TS2784: 'get' and 'set' accessors cannot declare 'this' parameters.
     }
     const contextual: Foo = {
         n: 16,