Improve error messages and always return any from newed functions

Previously, functions that specified a type for `this` would return that
type. Now they return `any`. This helps prevent unintentional use of this
feature when --noImplicitAny is turned on.

The type of `this` is still checked in the body of these functions.

src/compiler/checker.ts

@@ -5480,7 +5480,7 @@ namespace ts {
                     || compareTypes(target.thisType, source.thisType, reportErrors);
                 if (!related) {
                     if (reportErrors) {
-                        errorReporter(Diagnostics.Types_of_parameters_0_and_1_are_incompatible, "this", "this");
+                        errorReporter(Diagnostics.this_types_of_each_signature_are_incompatible);
                     }
                     return Ternary.False;
                 }
@@ -10223,7 +10223,7 @@ namespace ts {
                 const thisArgumentNode = getThisArgumentOfCall(node);
                 const thisArgumentType = thisArgumentNode ? checkExpression(thisArgumentNode) : voidType;
                 const errorNode = reportErrors ? (thisArgumentNode || node) : undefined;
-                const headMessage = Diagnostics.this_context_of_type_0_is_not_assignable_to_method_this_of_type_1;
+                const headMessage = Diagnostics.this_context_of_type_0_is_not_assignable_to_method_s_this_of_type_1;
                 if (!checkTypeRelatedTo(thisArgumentType, signature.thisType, relation, errorNode, headMessage)) {
                     return false;
                 }
@@ -10929,7 +10929,7 @@ namespace ts {
             // If expressionType's apparent type is an object type with no construct signatures but
             // one or more call signatures, the expression is processed as a function call. A compile-time
             // error occurs if the result of the function call is not Void. The type of the result of the
-            // operation is the function's this type. It is an error to have a Void this type.
+            // operation is Any. It is an error to have a Void this type.
             const callSignatures = getSignaturesOfType(expressionType, SignatureKind.Call);
             if (callSignatures.length) {
                 const signature = resolveCall(node, callSignatures, candidatesOutArray);
@@ -11117,10 +11117,10 @@ namespace ts {
                     if (funcSymbol && funcSymbol.members && (funcSymbol.flags & SymbolFlags.Function)) {
                         return getInferredClassType(funcSymbol);
                     }
-                    else if (compilerOptions.noImplicitAny && !signature.thisType) {
+                    else if (compilerOptions.noImplicitAny) {
                         error(node, Diagnostics.new_expression_whose_target_lacks_a_construct_signature_implicitly_has_an_any_type);
                     }
-                    return signature.thisType || anyType;
+                    return anyType;
                 }
             }
 

src/compiler/diagnosticMessages.json

@@ -1879,7 +1879,7 @@
         "category": "Error",
         "code": 2678
     },
-    "A function that is called with the 'new' keyword cannot have a 'this' type that is void.": {
+    "A function that is called with the 'new' keyword cannot have a 'this' type that is 'void'.": {
         "category": "Error",
         "code": 2679
     },
@@ -1899,10 +1899,14 @@
         "category": "Error",
         "code": 2683
     },
-    "'this' context of type '{0}' is not assignable to method 'this' of type '{1}'.": {
+    "'this' context of type '{0}' is not assignable to method's 'this' of type '{1}'.": {
         "category": "Error",
         "code": 2684
     },
+    "'this' types of each signature are incompatible.": {
+        "category": "Error",
+        "code": 2685
+    },
     "Import declaration '{0}' is using private name '{1}'.": {
         "category": "Error",
         "code": 4000

tests/baselines/reference/looseThisTypeInFunctions.errors.txt

@@ -1,8 +1,8 @@
 tests/cases/conformance/types/thisType/looseThisTypeInFunctions.ts(21,1): error TS2322: Type '(this: C, m: number) => number' is not assignable to type '(this: void, m: number) => number'.
-  Types of parameters 'this' and 'this' are incompatible.
+  'this' types of each signature are incompatible.
     Type 'void' is not assignable to type 'C'.
 tests/cases/conformance/types/thisType/looseThisTypeInFunctions.ts(33,28): error TS2339: Property 'length' does not exist on type 'number'.
-tests/cases/conformance/types/thisType/looseThisTypeInFunctions.ts(37,9): error TS2684: 'this' context of type 'void' is not assignable to method 'this' of type 'I'.
+tests/cases/conformance/types/thisType/looseThisTypeInFunctions.ts(37,9): error TS2684: 'this' context of type 'void' is not assignable to method's 'this' of type 'I'.
 tests/cases/conformance/types/thisType/looseThisTypeInFunctions.ts(46,20): error TS2339: Property 'length' does not exist on type 'number'.
 
 
@@ -30,7 +30,7 @@ tests/cases/conformance/types/thisType/looseThisTypeInFunctions.ts(46,20): error
     c.explicitVoid = c.explicitThis; // error, 'void' is missing everything
     ~~~~~~~~~~~~~~
 !!! error TS2322: Type '(this: C, m: number) => number' is not assignable to type '(this: void, m: number) => number'.
-!!! error TS2322:   Types of parameters 'this' and 'this' are incompatible.
+!!! error TS2322:   'this' types of each signature are incompatible.
 !!! error TS2322:     Type 'void' is not assignable to type 'C'.
     let o = { 
         n: 101,
@@ -51,7 +51,7 @@ tests/cases/conformance/types/thisType/looseThisTypeInFunctions.ts(46,20): error
     let x = i.explicitThis;
     let n = x(12); // callee:void doesn't match this:I
             ~~~~~
-!!! error TS2684: 'this' context of type 'void' is not assignable to method 'this' of type 'I'.
+!!! error TS2684: 'this' context of type 'void' is not assignable to method's 'this' of type 'I'.
     let u: Unused;
     let y = u.implicitNoThis;
     n = y(12); // ok, callee:void matches this:any

tests/baselines/reference/thisTypeInFunctions.types

@@ -895,13 +895,13 @@ function AnyThis(this: any) {
 >"ok" : string
 }
 let interfaceThis = new InterfaceThis();
->interfaceThis : I
->new InterfaceThis() : I
+>interfaceThis : any
+>new InterfaceThis() : any
 >InterfaceThis : (this: I) => void
 
 let literalTypeThis = new LiteralTypeThis();
->literalTypeThis : { x: string; }
->new LiteralTypeThis() : { x: string; }
+>literalTypeThis : any
+>new LiteralTypeThis() : any
 >LiteralTypeThis : (this: { x: string; }) => void
 
 let anyThis = new AnyThis();

tests/baselines/reference/thisTypeInFunctionsNegative.errors.txt

@@ -1,7 +1,7 @@
 tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(16,15): error TS2339: Property 'n' does not exist on type 'void'.
 tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(39,21): error TS2339: Property 'a' does not exist on type 'void'.
-tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(49,1): error TS2684: 'this' context of type 'void' is not assignable to method 'this' of type '{ a: number; }'.
-tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(51,1): error TS2684: 'this' context of type 'void' is not assignable to method 'this' of type 'I'.
+tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(49,1): error TS2684: 'this' context of type 'void' is not assignable to method's 'this' of type '{ a: number; }'.
+tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(51,1): error TS2684: 'this' context of type 'void' is not assignable to method's 'this' of type 'I'.
 tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(56,21): error TS2339: Property 'notFound' does not exist on type '{ y: number; }'.
 tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(59,21): error TS2339: Property 'notSpecified' does not exist on type 'void'.
 tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(61,79): error TS2322: Type '{ y: number; explicitStructural: (this: { y: number; }, x: number) => number; }' is not assignable to type '{ y: number; f: (this: { y: number; }, x: number) => number; }'.
@@ -13,10 +13,10 @@ tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(63,110): e
 tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(65,1): error TS2346: Supplied parameters do not match any signature of call target.
 tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(66,6): error TS2345: Argument of type 'string' is not assignable to parameter of type 'number'.
 tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(67,1): error TS2346: Supplied parameters do not match any signature of call target.
-tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(68,1): error TS2684: 'this' context of type '{ y: string; f: (this: { y: number; }, x: number) => number; }' is not assignable to method 'this' of type '{ y: number; }'.
+tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(68,1): error TS2684: 'this' context of type '{ y: string; f: (this: { y: number; }, x: number) => number; }' is not assignable to method's 'this' of type '{ y: number; }'.
   Types of property 'y' are incompatible.
     Type 'string' is not assignable to type 'number'.
-tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(69,1): error TS2684: 'this' context of type '{ wrongName: number; f: (this: { y: number; }, x: number) => number; }' is not assignable to method 'this' of type '{ y: number; }'.
+tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(69,1): error TS2684: 'this' context of type '{ wrongName: number; f: (this: { y: number; }, x: number) => number; }' is not assignable to method's 'this' of type '{ y: number; }'.
   Property 'y' is missing in type '{ wrongName: number; f: (this: { y: number; }, x: number) => number; }'.
 tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(72,1): error TS2346: Supplied parameters do not match any signature of call target.
 tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(73,13): error TS2345: Argument of type 'string' is not assignable to parameter of type 'number'.
@@ -31,49 +31,49 @@ tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(81,1): err
 tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(82,20): error TS2345: Argument of type 'string' is not assignable to parameter of type 'number'.
 tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(83,1): error TS2346: Supplied parameters do not match any signature of call target.
 tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(86,5): error TS2322: Type '(this: { y: number; }, x: number) => number' is not assignable to type '(this: void, x: number) => number'.
-  Types of parameters 'this' and 'this' are incompatible.
+  'this' types of each signature are incompatible.
     Type 'void' is not assignable to type '{ y: number; }'.
 tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(107,1): error TS2322: Type '(this: D, m: number) => number' is not assignable to type '(this: C, m: number) => number'.
-  Types of parameters 'this' and 'this' are incompatible.
+  'this' types of each signature are incompatible.
     Type 'C' is not assignable to type 'D'.
       Property 'x' is missing in type 'C'.
 tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(108,1): error TS2322: Type '(this: { x: number; }, m: number) => number' is not assignable to type '(this: { n: number; }, m: number) => number'.
-  Types of parameters 'this' and 'this' are incompatible.
+  'this' types of each signature are incompatible.
     Type '{ n: number; }' is not assignable to type '{ x: number; }'.
       Property 'x' is missing in type '{ n: number; }'.
 tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(110,1): error TS2322: Type '(this: D, m: number) => number' is not assignable to type '(this: C, m: number) => number'.
-  Types of parameters 'this' and 'this' are incompatible.
+  'this' types of each signature are incompatible.
     Type 'C' is not assignable to type 'D'.
 tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(111,1): error TS2322: Type '(this: D, m: number) => number' is not assignable to type '(this: C, m: number) => number'.
-  Types of parameters 'this' and 'this' are incompatible.
+  'this' types of each signature are incompatible.
     Type 'C' is not assignable to type 'D'.
 tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(112,1): error TS2322: Type '(this: D, m: number) => number' is not assignable to type '(this: C, m: number) => number'.
-  Types of parameters 'this' and 'this' are incompatible.
+  'this' types of each signature are incompatible.
     Type 'C' is not assignable to type 'D'.
 tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(113,1): error TS2322: Type '(this: D, m: number) => number' is not assignable to type '(this: C, m: number) => number'.
-  Types of parameters 'this' and 'this' are incompatible.
+  'this' types of each signature are incompatible.
     Type 'C' is not assignable to type 'D'.
 tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(114,1): error TS2322: Type '(this: D, m: number) => number' is not assignable to type '(this: { n: number; }, m: number) => number'.
-  Types of parameters 'this' and 'this' are incompatible.
+  'this' types of each signature are incompatible.
     Type '{ n: number; }' is not assignable to type 'D'.
       Property 'x' is missing in type '{ n: number; }'.
 tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(115,1): error TS2322: Type '(this: D, m: number) => number' is not assignable to type '(this: C, m: number) => number'.
 tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(116,1): error TS2322: Type '(this: D, m: number) => number' is not assignable to type '(this: void, m: number) => number'.
-  Types of parameters 'this' and 'this' are incompatible.
+  'this' types of each signature are incompatible.
     Type 'void' is not assignable to type 'D'.
 tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(117,1): error TS2322: Type '(this: D, m: number) => number' is not assignable to type '(this: void, m: number) => number'.
-  Types of parameters 'this' and 'this' are incompatible.
+  'this' types of each signature are incompatible.
     Type 'void' is not assignable to type 'D'.
 tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(125,69): error TS2339: Property 'x' does not exist on type 'typeof Base1'.
 tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(145,1): error TS2322: Type '(this: Base2) => number' is not assignable to type '(this: Base1) => number'.
-  Types of parameters 'this' and 'this' are incompatible.
+  'this' types of each signature are incompatible.
     Type 'Base1' is not assignable to type 'Base2'.
       Property 'y' is missing in type 'Base1'.
 tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(146,1): error TS2322: Type '(this: Base2) => number' is not assignable to type '(this: Base1) => number'.
-  Types of parameters 'this' and 'this' are incompatible.
+  'this' types of each signature are incompatible.
     Type 'Base1' is not assignable to type 'Base2'.
 tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(148,1): error TS2322: Type '(this: Base2) => number' is not assignable to type '(this: Base1) => number'.
-tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(154,16): error TS2679: A function that is called with the 'new' keyword cannot have a 'this' type that is void.
+tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(154,16): error TS2679: A function that is called with the 'new' keyword cannot have a 'this' type that is 'void'.
 tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(158,17): error TS2681: A constructor cannot have a 'this' parameter.
 tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(160,11): error TS2682: A setter cannot have a 'this' parameter.
 tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(164,9): error TS2681: A constructor cannot have a 'this' parameter.
@@ -154,11 +154,11 @@ tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(176,35): e
     let implExplicitStructural = impl.explicitStructural;
     implExplicitStructural(); // error, no 'a' in 'void'
     ~~~~~~~~~~~~~~~~~~~~~~~~
-!!! error TS2684: 'this' context of type 'void' is not assignable to method 'this' of type '{ a: number; }'.
+!!! error TS2684: 'this' context of type 'void' is not assignable to method's 'this' of type '{ a: number; }'.
     let implExplicitInterface = impl.explicitInterface;
     implExplicitInterface(); // error, no 'a' in 'void' 
     ~~~~~~~~~~~~~~~~~~~~~~~
-!!! error TS2684: 'this' context of type 'void' is not assignable to method 'this' of type 'I'.
+!!! error TS2684: 'this' context of type 'void' is not assignable to method's 'this' of type 'I'.
     function explicitStructural(this: { y: number }, x: number): number {
         return x + this.y;
     }
@@ -196,12 +196,12 @@ tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(176,35): e
 !!! error TS2346: Supplied parameters do not match any signature of call target.
     wrongPropertyType.f(13);
     ~~~~~~~~~~~~~~~~~
-!!! error TS2684: 'this' context of type '{ y: string; f: (this: { y: number; }, x: number) => number; }' is not assignable to method 'this' of type '{ y: number; }'.
+!!! error TS2684: 'this' context of type '{ y: string; f: (this: { y: number; }, x: number) => number; }' is not assignable to method's 'this' of type '{ y: number; }'.
 !!! error TS2684:   Types of property 'y' are incompatible.
 !!! error TS2684:     Type 'string' is not assignable to type 'number'.
     wrongPropertyName.f(13);
     ~~~~~~~~~~~~~~~~~
-!!! error TS2684: 'this' context of type '{ wrongName: number; f: (this: { y: number; }, x: number) => number; }' is not assignable to method 'this' of type '{ y: number; }'.
+!!! error TS2684: 'this' context of type '{ wrongName: number; f: (this: { y: number; }, x: number) => number; }' is not assignable to method's 'this' of type '{ y: number; }'.
 !!! error TS2684:   Property 'y' is missing in type '{ wrongName: number; f: (this: { y: number; }, x: number) => number; }'.
     
     let c = new C();
@@ -246,7 +246,7 @@ tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(176,35): e
     let specifiedToVoid: (this: void, x: number) => number = explicitStructural;
         ~~~~~~~~~~~~~~~
 !!! error TS2322: Type '(this: { y: number; }, x: number) => number' is not assignable to type '(this: void, x: number) => number'.
-!!! error TS2322:   Types of parameters 'this' and 'this' are incompatible.
+!!! error TS2322:   'this' types of each signature are incompatible.
 !!! error TS2322:     Type 'void' is not assignable to type '{ y: number; }'.
     
     let reconstructed: { 
@@ -271,40 +271,40 @@ tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(176,35): e
     c.explicitC = function(this: D, m: number) { return this.x + m };
     ~~~~~~~~~~~
 !!! error TS2322: Type '(this: D, m: number) => number' is not assignable to type '(this: C, m: number) => number'.
-!!! error TS2322:   Types of parameters 'this' and 'this' are incompatible.
+!!! error TS2322:   'this' types of each signature are incompatible.
 !!! error TS2322:     Type 'C' is not assignable to type 'D'.
 !!! error TS2322:       Property 'x' is missing in type 'C'.
     c.explicitProperty = explicitXProperty;
     ~~~~~~~~~~~~~~~~~~
 !!! error TS2322: Type '(this: { x: number; }, m: number) => number' is not assignable to type '(this: { n: number; }, m: number) => number'.
-!!! error TS2322:   Types of parameters 'this' and 'this' are incompatible.
+!!! error TS2322:   'this' types of each signature are incompatible.
 !!! error TS2322:     Type '{ n: number; }' is not assignable to type '{ x: number; }'.
 !!! error TS2322:       Property 'x' is missing in type '{ n: number; }'.
     
     c.explicitC = d.explicitD;
     ~~~~~~~~~~~
 !!! error TS2322: Type '(this: D, m: number) => number' is not assignable to type '(this: C, m: number) => number'.
-!!! error TS2322:   Types of parameters 'this' and 'this' are incompatible.
+!!! error TS2322:   'this' types of each signature are incompatible.
 !!! error TS2322:     Type 'C' is not assignable to type 'D'.
     c.explicitC = d.explicitThis;
     ~~~~~~~~~~~
 !!! error TS2322: Type '(this: D, m: number) => number' is not assignable to type '(this: C, m: number) => number'.
-!!! error TS2322:   Types of parameters 'this' and 'this' are incompatible.
+!!! error TS2322:   'this' types of each signature are incompatible.
 !!! error TS2322:     Type 'C' is not assignable to type 'D'.
     c.explicitThis = d.explicitD;
     ~~~~~~~~~~~~~~
 !!! error TS2322: Type '(this: D, m: number) => number' is not assignable to type '(this: C, m: number) => number'.
-!!! error TS2322:   Types of parameters 'this' and 'this' are incompatible.
+!!! error TS2322:   'this' types of each signature are incompatible.
 !!! error TS2322:     Type 'C' is not assignable to type 'D'.
     c.explicitThis = d.explicitThis;
     ~~~~~~~~~~~~~~
 !!! error TS2322: Type '(this: D, m: number) => number' is not assignable to type '(this: C, m: number) => number'.
-!!! error TS2322:   Types of parameters 'this' and 'this' are incompatible.
+!!! error TS2322:   'this' types of each signature are incompatible.
 !!! error TS2322:     Type 'C' is not assignable to type 'D'.
     c.explicitProperty = d.explicitD;
     ~~~~~~~~~~~~~~~~~~
 !!! error TS2322: Type '(this: D, m: number) => number' is not assignable to type '(this: { n: number; }, m: number) => number'.
-!!! error TS2322:   Types of parameters 'this' and 'this' are incompatible.
+!!! error TS2322:   'this' types of each signature are incompatible.
 !!! error TS2322:     Type '{ n: number; }' is not assignable to type 'D'.
 !!! error TS2322:       Property 'x' is missing in type '{ n: number; }'.
     c.explicitThis = d.explicitThis;
@@ -313,12 +313,12 @@ tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(176,35): e
     c.explicitVoid = d.explicitD;
     ~~~~~~~~~~~~~~
 !!! error TS2322: Type '(this: D, m: number) => number' is not assignable to type '(this: void, m: number) => number'.
-!!! error TS2322:   Types of parameters 'this' and 'this' are incompatible.
+!!! error TS2322:   'this' types of each signature are incompatible.
 !!! error TS2322:     Type 'void' is not assignable to type 'D'.
     c.explicitVoid = d.explicitThis;
     ~~~~~~~~~~~~~~
 !!! error TS2322: Type '(this: D, m: number) => number' is not assignable to type '(this: void, m: number) => number'.
-!!! error TS2322:   Types of parameters 'this' and 'this' are incompatible.
+!!! error TS2322:   'this' types of each signature are incompatible.
 !!! error TS2322:     Type 'void' is not assignable to type 'D'.
     
     /// class-based polymorphic assignability (with inheritance!) ///
@@ -352,13 +352,13 @@ tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(176,35): e
     b1.polymorphic = b2.polymorphic // error, 'this.y' not in Base1: { x }
     ~~~~~~~~~~~~~~
 !!! error TS2322: Type '(this: Base2) => number' is not assignable to type '(this: Base1) => number'.
-!!! error TS2322:   Types of parameters 'this' and 'this' are incompatible.
+!!! error TS2322:   'this' types of each signature are incompatible.
 !!! error TS2322:     Type 'Base1' is not assignable to type 'Base2'.
 !!! error TS2322:       Property 'y' is missing in type 'Base1'.
     b1.explicit = b2.polymorphic // error, 'y' not in Base1: { x }
     ~~~~~~~~~~~
 !!! error TS2322: Type '(this: Base2) => number' is not assignable to type '(this: Base1) => number'.
-!!! error TS2322:   Types of parameters 'this' and 'this' are incompatible.
+!!! error TS2322:   'this' types of each signature are incompatible.
 !!! error TS2322:     Type 'Base1' is not assignable to type 'Base2'.
     
     d1.explicit = b2.polymorphic // error, 'y' not in Base1: { x }
@@ -371,7 +371,7 @@ tests/cases/conformance/types/thisType/thisTypeInFunctionsNegative.ts(176,35): e
     }
     let voidThis = new VoidThis();
                    ~~~~~~~~~~~~~~
-!!! error TS2679: A function that is called with the 'new' keyword cannot have a 'this' type that is void.
+!!! error TS2679: A function that is called with the 'new' keyword cannot have a 'this' type that is 'void'.
     
     ///// syntax-ish errors /////
     class ThisConstructor {