fix: remove default constructors and require explicit construct new() for all user classes

The compiler no longer auto-generates a default `new()` constructor for classes. All classes must now explicitly define `construct new() {}` to be instantiable. This change removes the `createDefaultConstructor` function from the compiler, eliminates the `return_this` primitive used by Object's default initializer, and adds explicit constructors to all test and example classes. Core metaclasses (Bool, Class, Null, Num, Object, Range, Sequence) now correctly reject `new()` calls with runtime errors.

test/core/bool/no_constructor.wren

@@ -0,0 +1 @@
+Bool.new() // expect runtime error: Bool metaclass does not implement 'new()'.

test/core/class/no_constructor.wren

@@ -0,0 +1 @@
+Class.new() // expect runtime error: Class does not implement 'new()'.

test/core/list/join.wren

@@ -15,6 +15,7 @@ IO.print([1, [2, [3], 4], 5].join(",")) // expect: 1,[2, [3], 4],5
 
 // Calls toString on elements.
 class Foo {
+  construct new() {}
   toString { "Foo.toString" }
 }
 

test/core/list/to_string.wren

@@ -9,6 +9,7 @@ IO.print([1, [2, [3], 4], 5]) // expect: [1, [2, [3], 4], 5]
 
 // Calls toString on elements.
 class Foo {
+  construct new() {}
   toString { "Foo.toString" }
 }
 

test/core/map/to_string.wren

@@ -9,6 +9,7 @@ IO.print({1: {2: {}}}) // expect: {1: {2: {}}}
 
 // Calls toString on elements.
 class Foo {
+  construct new() {}
   toString { "Foo.toString" }
 }
 

test/core/null/no_constructor.wren

@@ -0,0 +1 @@
+Null.new() // expect runtime error: Null metaclass does not implement 'new()'.

test/core/number/no_constructor.wren

@@ -0,0 +1 @@
+Num.new() // expect runtime error: Num metaclass does not implement 'new()'.

test/core/object/no_constructor.wren

@@ -0,0 +1 @@
+Object.new() // expect runtime error: Object metaclass does not implement 'new()'.

test/core/object/not.wren

@@ -1,2 +1,4 @@
-class Foo {}
+class Foo {
+  construct new() {}
+}
 IO.print(!Foo.new()) // expect: false

test/core/object/same.wren

@@ -24,7 +24,9 @@ IO.print(Object.same(Bool, Num)) // expect: false
 IO.print(Object.same(Bool, Bool)) // expect: true
 
 // Other types compare by identity.
-class Foo {}
+class Foo {
+  construct new() {}
+}
 
 var foo = Foo.new()
 IO.print(Object.same(foo, foo)) // expect: true
@@ -32,6 +34,7 @@ IO.print(Object.same(foo, Foo.new())) // expect: false
 
 // Ignores == operators.
 class Bar {
+  construct new() {}
   ==(other) { true }
 }
 

test/core/object/to_string.wren

@@ -1,2 +1,4 @@
-class Foo {}
+class Foo {
+  construct new() {}
+}
 IO.print(Foo.new().toString == "instance of Foo") // expect: true

test/core/range/no_constructor.wren

@@ -0,0 +1 @@
+Range.new() // expect runtime error: Range metaclass does not implement 'new()'.

test/core/sequence/count.wren

@@ -1,4 +1,6 @@
 class TestSequence is Sequence {
+  construct new() {}
+
   iterate(iterator) {
     if (iterator == null) return 1
     if (iterator == 10) return false

test/core/sequence/is_empty.wren

@@ -2,6 +2,7 @@ IO.print([].isEmpty) // expect: true
 IO.print([1].isEmpty) // expect: false
 
 class InfiniteSequence is Sequence {
+  construct new() {}
   iterate(iterator) { true }
   iteratorValue(iterator) { iterator }
 }

test/core/sequence/map.wren

@@ -15,6 +15,8 @@ class FibIterator {
 }
 
 class Fib is Sequence {
+  construct new() {}
+
   iterate(iterator) {
     if (iterator == null) return FibIterator.new()
     iterator.iterate

test/core/sequence/no_constructor.wren

@@ -0,0 +1 @@
+Sequence.new() // expect runtime error: Sequence metaclass does not implement 'new()'.

test/core/sequence/to_list.wren

@@ -1,4 +1,6 @@
 class TestSequence is Sequence {
+  construct new() {}
+
   iterate(iterator) {
     if (iterator == null) return 1
     if (iterator == 3) return false

test/core/sequence/where.wren

@@ -15,6 +15,8 @@ class FibIterator {
 }
 
 class Fib is Sequence {
+  construct new() {}
+
   iterate(iterator) {
     if (iterator == null) return FibIterator.new()
     iterator.iterate

test/core/string/no_constructor.wren

@@ -0,0 +1 @@
+String.new() // expect runtime error: String metaclass does not implement 'new()'.