Issue 6378 - [emscripten] Make DependentString constexpr

test/compiled/String.cpp

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 #include <string>
 #include <gtest/gtest.h>
 #include "compiled/String.h"
 
 ABP_NS_USING
 
+TEST(TestString, checkConstexprCorrectness)
+{
+  static constexpr DependentString s(u"Hello world!");
+  static_assert(s.length() == 12, "Length should be 12");
+
+  EXPECT_FALSE(s.is_writable());

[sergei, 2018/03/14 16:57:44]

I wonder whether it should be static_assert too.

[René Jeschke, 2018/03/14 17:01:00]

Yeah, was thinking about this, too. I wasn't sure if I can have a test case
without any 'tests'. And: if 's.length()' works without errors, the other
functions should, too, as the static assert makes sure, that we really have a
constexpr value.

I can, add more static_asserts, one for each 'constexpr' method, if wanted.

[sergei, 2018/03/14 17:03:09]

I think it's fine, JIC technically it's possible.
That would be very good too.

[René Jeschke, 2018/03/14 17:12:22]

Done.

+}
+
 TEST(TestString, constructInvalidDependentString)
 {
   DependentString s;
   EXPECT_TRUE(s.is_invalid());
 
   DependentString s2(s);
   EXPECT_TRUE(s2.is_invalid());
 }
 
 TEST(TestString, constructInvalidOwnedString)
@@ skipping 134 matching lines @@
   EXPECT_FALSE(lexical_cast<bool>(u"some-string"_str));
   EXPECT_FALSE(lexical_cast<bool>(u""_str));
   EXPECT_FALSE(lexical_cast<bool>(DependentString()));
 }
 
 TEST(TestStringLexicalCast, toOwnedString)
 {
   EXPECT_EQ(u"some-string"_str, lexical_cast<OwnedString>(u"some-string"_str));
   EXPECT_EQ(u""_str, lexical_cast<OwnedString>(u""_str));
 }