CppEditor: More special rendering for string literals

Display prefixes and suffixes different from the actual string, like we
already did for raw string literals.
This uncovered some minor bugs in both lexer and highlighter:
  - Wrong length for a setFormat() call in highlightRawStringLiteral()
  - Missing check for user-defined literal in raw string literals
  - Missing check for user-defined literal in multi-line strings

Fixes: QTCREATORBUG-28869
Change-Id: I018717c50ddc1d09c609556161c85dfb0cc29fab
Reviewed-by: David Schulz <david.schulz@qt.io>

4 files changed, 97 insertions, 8 deletions

diff --git a/src/libs/3rdparty/cplusplus/Lexer.cpp b/src/libs/3rdparty/cplusplus/Lexer.cpp
index e2f1b4e0e6..fc1b72cb7d 100644
--- a/src/libs/3rdparty/cplusplus/Lexer.cpp
+++ b/src/libs/3rdparty/cplusplus/Lexer.cpp
@@ -217,14 +217,17 @@ void Lexer::scan_helper(Token *tok)
         tok->f.kind = s._tokenKind;
         const bool found = _expectedRawStringSuffix.isEmpty()
                 ? scanUntilRawStringLiteralEndSimple() : scanUntilRawStringLiteralEndPrecise();
-        if (found)
+        if (found) {
+            scanOptionalUserDefinedLiteral(tok);
             _state = 0;
+        }
         return;
     } else { // non-raw strings
         tok->f.joined = true;
         tok->f.kind = s._tokenKind;
         _state = 0;
         scanUntilQuote(tok, '"');
+        scanOptionalUserDefinedLiteral(tok);
         return;
     }
 
@@ -829,6 +832,8 @@ void Lexer::scanRawStringLiteral(Token *tok, unsigned char hint)
         _expectedRawStringSuffix.prepend(')');
         _expectedRawStringSuffix.append('"');
     }
+    if (closed)
+        scanOptionalUserDefinedLiteral(tok);
 }
 
 bool Lexer::scanUntilRawStringLiteralEndPrecise()
diff --git a/src/plugins/cppeditor/cpphighlighter.cpp b/src/plugins/cppeditor/cpphighlighter.cpp
index 0f9184600b..87e36491ad 100644
--- a/src/plugins/cppeditor/cpphighlighter.cpp
+++ b/src/plugins/cppeditor/cpphighlighter.cpp
@@ -161,10 +161,8 @@ void CppHighlighter::highlightBlock(const QString &text)
         } else if (tk.is(T_NUMERIC_LITERAL)) {
             setFormat(tk.utf16charsBegin(), tk.utf16chars(), formatForCategory(C_NUMBER));
         } else if (tk.isStringLiteral() || tk.isCharLiteral()) {
-            if (!highlightRawStringLiteral(text, tk, QString::fromUtf8(inheritedRawStringSuffix))) {
-                setFormatWithSpaces(text, tk.utf16charsBegin(), tk.utf16chars(),
-                                    formatForCategory(C_STRING));
-            }
+            if (!highlightRawStringLiteral(text, tk, QString::fromUtf8(inheritedRawStringSuffix)))
+                highlightStringLiteral(text, tk);
         } else if (tk.isComment()) {
             const int startPosition = initialLexerState ? previousTokenEnd : tk.utf16charsBegin();
             if (tk.is(T_COMMENT) || tk.is(T_CPP_COMMENT)) {
@@ -413,8 +411,18 @@ bool CppHighlighter::highlightRawStringLiteral(QStringView text, const Token &tk
         stringOffset = delimiterOffset + delimiter.length() + 1;
         stringLength -= delimiter.length() + 1;
     }();
-    if (text.mid(tk.utf16charsBegin(), tk.utf16chars()).endsWith(expectedSuffix)) {
-        endDelimiterOffset = tk.utf16charsBegin() + tk.utf16chars() - expectedSuffix.size();
+    int operatorOffset = tk.utf16charsBegin() + tk.utf16chars();
+    int operatorLength = 0;
+    if (tk.f.userDefinedLiteral) {
+        const int closingQuoteOffset = text.lastIndexOf('"', operatorOffset);
+        QTC_ASSERT(closingQuoteOffset >= tk.utf16charsBegin(), return false);
+        operatorOffset = closingQuoteOffset + 1;
+        operatorLength = tk.utf16charsBegin() + tk.utf16chars() - operatorOffset;
+        stringLength -= operatorLength;
+    }
+    if (text.mid(tk.utf16charsBegin(), operatorOffset - tk.utf16charsBegin())
+            .endsWith(expectedSuffix)) {
+        endDelimiterOffset = operatorOffset - expectedSuffix.size();
         stringLength -= expectedSuffix.size();
     }
 
@@ -422,13 +430,52 @@ bool CppHighlighter::highlightRawStringLiteral(QStringView text, const Token &tk
     //             a string, and the rest (including the delimiter) as a keyword.
     const QTextCharFormat delimiterFormat = formatForCategory(C_KEYWORD);
     if (delimiterOffset != -1)
-        setFormat(tk.utf16charsBegin(), stringOffset, delimiterFormat);
+        setFormat(tk.utf16charsBegin(), stringOffset - tk.utf16charsBegin(), delimiterFormat);
     setFormatWithSpaces(text.toString(), stringOffset, stringLength, formatForCategory(C_STRING));
     if (endDelimiterOffset != -1)
         setFormat(endDelimiterOffset, expectedSuffix.size(), delimiterFormat);
+    if (operatorLength > 0)
+        setFormat(operatorOffset, operatorLength, formatForCategory(C_OPERATOR));
     return true;
 }
 
+void CppHighlighter::highlightStringLiteral(QStringView text, const CPlusPlus::Token &tk)
+{
+    switch (tk.kind()) {
+    case T_WIDE_STRING_LITERAL:
+    case T_UTF8_STRING_LITERAL:
+    case T_UTF16_STRING_LITERAL:
+    case T_UTF32_STRING_LITERAL:
+        break;
+    default:
+        if (!tk.userDefinedLiteral()) { // Simple case: No prefix, no suffix.
+            setFormatWithSpaces(text.toString(), tk.utf16charsBegin(), tk.utf16chars(),
+                                formatForCategory(C_STRING));
+            return;
+        }
+    }
+
+    int stringOffset = 0;
+    if (!tk.f.joined) {
+        stringOffset = text.indexOf('"', tk.utf16charsBegin());
+        QTC_ASSERT(stringOffset > 0, return);
+        setFormat(tk.utf16charsBegin(), stringOffset - tk.utf16charsBegin(),
+                  formatForCategory(C_KEYWORD));
+    }
+    int operatorOffset = tk.utf16charsBegin() + tk.utf16chars();
+    if (tk.userDefinedLiteral()) {
+        const int closingQuoteOffset = text.lastIndexOf('"', operatorOffset);
+        QTC_ASSERT(closingQuoteOffset >= tk.utf16charsBegin(), return);
+        operatorOffset = closingQuoteOffset + 1;
+    }
+    setFormatWithSpaces(text.toString(), stringOffset, operatorOffset - tk.utf16charsBegin(),
+                        formatForCategory(C_STRING));
+    if (const int operatorLength = tk.utf16charsBegin() + tk.utf16chars() - operatorOffset;
+        operatorLength > 0) {
+        setFormat(operatorOffset, operatorLength, formatForCategory(C_OPERATOR));
+    }
+}
+
 void CppHighlighter::highlightDoxygenComment(const QString &text, int position, int)
 {
     int initial = position;
@@ -514,6 +561,32 @@ void CppHighlighterTest::test_data()
     QTest::newRow("operator keyword") << 26 << 5 << 26 << 12 << C_KEYWORD;
     QTest::newRow("type in conversion operator") << 26 << 14 << 26 << 16 << C_PRIMITIVE_TYPE;
     QTest::newRow("concept keyword") << 29 << 22 << 29 << 28 << C_KEYWORD;
+    QTest::newRow("user-defined UTF-16 string literal (prefix)")
+        << 32 << 16 << 32 << 16 << C_KEYWORD;
+    QTest::newRow("user-defined UTF-16 string literal (content)")
+        << 32 << 17 << 32 << 21 << C_STRING;
+    QTest::newRow("user-defined UTF-16 string literal (suffix)")
+        << 32 << 22 << 32 << 23 << C_OPERATOR;
+    QTest::newRow("wide string literal (prefix)") << 33 << 17 << 33 << 17 << C_KEYWORD;
+    QTest::newRow("wide string literal (content)") << 33 << 18 << 33 << 24 << C_STRING;
+    QTest::newRow("UTF-8 string literal (prefix)") << 34 << 17 << 34 << 18 << C_KEYWORD;
+    QTest::newRow("UTF-8 string literal (content)") << 34 << 19 << 34 << 24 << C_STRING;
+    QTest::newRow("UTF-32 string literal (prefix)") << 35 << 17 << 35 << 17 << C_KEYWORD;
+    QTest::newRow("UTF-8 string literal (content)") << 35 << 18 << 35 << 23 << C_STRING;
+    QTest::newRow("user-defined UTF-16 raw string literal (prefix)")
+        << 36 << 17 << 36 << 20 << C_KEYWORD;
+    QTest::newRow("user-defined UTF-16 raw string literal (content)")
+        << 36 << 38 << 37 << 8 << C_STRING;
+    QTest::newRow("user-defined UTF-16 raw string literal (suffix 1)")
+        << 37 << 9 << 37 << 10 << C_KEYWORD;
+    QTest::newRow("user-defined UTF-16 raw string literal (suffix 2)")
+        << 37 << 11 << 37 << 12 << C_OPERATOR;
+    QTest::newRow("multi-line user-defined UTF-16 string literal (prefix)")
+        << 38 << 17 << 38 << 17 << C_KEYWORD;
+    QTest::newRow("multi-line user-defined UTF-16 string literal (content)")
+        << 38 << 18 << 39 << 3 << C_STRING;
+    QTest::newRow("multi-line user-defined UTF-16 string literal (suffix)")
+        << 39 << 4 << 39 << 5 << C_OPERATOR;
 }
 
 void CppHighlighterTest::test()
diff --git a/src/plugins/cppeditor/cpphighlighter.h b/src/plugins/cppeditor/cpphighlighter.h
index 358fcb2760..1728ffeb77 100644
--- a/src/plugins/cppeditor/cpphighlighter.h
+++ b/src/plugins/cppeditor/cpphighlighter.h
@@ -29,6 +29,7 @@ private:
     void highlightWord(QStringView word, int position, int length);
     bool highlightRawStringLiteral(QStringView text, const CPlusPlus::Token &tk,
                                    const QString &inheritedSuffix);
+    void highlightStringLiteral(QStringView text, const CPlusPlus::Token &tk);
 
     void highlightDoxygenComment(const QString &text, int position,
                                  int length);
diff --git a/src/plugins/cppeditor/testcases/highlightingtestcase.cpp b/src/plugins/cppeditor/testcases/highlightingtestcase.cpp
index 770b22e553..dd1f9c1b3e 100644
--- a/src/plugins/cppeditor/testcases/highlightingtestcase.cpp
+++ b/src/plugins/cppeditor/testcases/highlightingtestcase.cpp
@@ -27,3 +27,13 @@ struct ConversionFunction {
 };
 
 template<typename T> concept NoConstraint = true;
+
+const char16_t *operator ""_w(const char16_t *s, size_t) { return s; }
+const auto s = u"one"_w;
+const auto s2 = L"hello";
+const auto s3 = u8"hello";
+const auto s4 = U"hello";
+const auto s5 = uR"("o
+     ne")"_w;
+const auto s6 = u"o\
+ne"_w;