Invoking constructors changes global this instead of newTarget

[tofpie]

Describe the bug
String used as a function call messes up with the global object.

To Reproduce

This JavaScript code reproduces the issue:

String(10)
this.length
String.prototype.toString.call(this)

Running this code, 2 is printed as this.length and "10" is printed as String.prototype.toString.call(this).

Expected behavior
Running this code, this.length should stay undefined and String.prototype.toString.call(this) should throw a TypeError.

Build environment (please complete the following information):

• OS: Windows 10
• Version: 0.10
• Target triple: x86_64-pc-windows-msvc
• Rustc version: rustc 1.48.0 (7eac88abb 2020-11-16)

Additional context
None

[tofpie]

This is this part that messes up with the global object when String is called directly:

boa/boa/src/builtins/string/mod.rs

Lines 132 to 153 in 67ee6fa

	pub(crate) fn constructor(
	this: &Value,
	args: &[Value],
	context: &mut Context,
	) -> Result<Value> {
	// This value is used by console.log and other routines to match Obexpecty"failed to parse argument for String method"pe
	// to its Javascript Identifier (global constructor method name)
	let string = match args.get(0) {
	Some(ref value) => value.to_string(context)?,
	None => RcString::default(),
	};
	let length = DataDescriptor::new(
	Value::from(string.encode_utf16().count()),
	Attribute::NON_ENUMERABLE,
	);
	this.set_property("length", length);
	this.set_data(ObjectData::String(string.clone()));
	Ok(Value::from(string))
	}

But I really do not know how to fix that. If anyone has some guidance, I can give it a try though.

[RageKnify]

I think this can happen with most builtin constructors, we can generate a similar effect with:

>>  Boolean()
>> this
Boolean { false }

I assume we need to change most of the constructors, the spec mentions newTarget, which I think can be found in boa in

boa/boa/src/environment/function_environment_record.rs

Line 57 in 7b103a5

pub new_target: Value,

rust-analyzer only spots it only as being declared and initialized so it seems it currently isn't used.