playlist/cue/CueParser: use std::string_view in public API

src/playlist/cue/CueParser.cxx

@@ -19,8 +19,8 @@
 
 #include "CueParser.hxx"
 #include "tag/ParseName.hxx"
-#include "util/StringView.hxx"
 #include "util/CharUtil.hxx"
+#include "util/StringView.hxx"
 
 #include <algorithm>
 #include <cassert>
@@ -110,7 +110,7 @@ CueParser::GetCurrentTag() noexcept
 }
 
 static bool
-IsDigit(StringView s) noexcept
+IsDigit(std::string_view s) noexcept
 {
 	return !s.empty() && IsDigitASCII(s.front());
 }
@@ -174,10 +174,12 @@ CueParser::Commit() noexcept
 }
 
 void
-CueParser::Feed(StringView src) noexcept
+CueParser::Feed(std::string_view _src) noexcept
 {
 	assert(!end);
 
+	StringView src{_src};
+
 	auto command = cue_next_token(src);
 	if (command == nullptr)
 		return;

src/playlist/cue/CueParser.hxx

@@ -24,10 +24,9 @@
 #include "tag/Builder.hxx"
 #include "util/Compiler.h"
 
-#include <string>
 #include <memory>
-
-struct StringView;
+#include <string>
+#include <string_view>
 
 class CueParser {
 	enum {
@@ -106,7 +105,7 @@ public:
 	 * Feed a text line from the CUE file into the parser.  Call
 	 * Get() after this to see if a song has been finished.
 	 */
-	void Feed(StringView line) noexcept;
+	void Feed(std::string_view line) noexcept;
 
 	/**
 	 * Tell the parser that the end of the file has been reached.  Call