Don't optimize string literals to string.const if they are not valid UTF-16 strings.

[rluble]

No description provided.

[kripken]

lgtm otherwise, thanks! And sorry for the multiple iterations here.

[kripken]

I think the best place for this might be

src/support/string.h, cpp

alongside the existing isUTF8.

[rluble]

How do I go about the Literal representation and std::string_view or std:string? I assume we don't want isValidUtf16Literal taking a Literal in string.cpp.

[kripken]

Hmm, we have related logic here:

binaryen/src/wasm/literal.cpp

Lines 660 to 677 in 5f767b7

	case HeapType::string: {
	auto data = literal.getGCData();
	if (!data) {
	o << "nullstring";
	} else {
	o << "string(";
	// Convert WTF-16 literals to WTF-16 string.
	std::stringstream wtf16;
	for (auto c : data->values) {
	auto u = c.getInteger();
	assert(u < 0x10000);
	wtf16 << uint8_t(u & 0xFF);
	wtf16 << uint8_t(u >> 8);
	}
	// Escape to ensure we have valid unicode output and to make
	// unprintable characters visible.
	// TODO: Use wtf16.view() once we have C++20.
	String::printEscapedJSON(o, wtf16.str());

Perhaps in this PR we can leave it as is and just add a TODO, something like

// TODO: move this logic to src/support/string, and refactor to share code with wasm/literal.cpp string printing's conversion from a Literal to a raw string

[rluble]

sg. Added a TODO. Thanks.