[Clang] Handle static_assert messages with an expression started by a literal

[tbaeder]

clang/lib/Parse/ParseDeclCXX.cpp

1019–1032

[cor3ntin]

clang/lib/Parse/ParseDeclCXX.cpp

1019–1032

Oups, thanks!

[aaron.ballman]

LGTM aside from minor nits.

clang/lib/Parse/ParseDeclCXX.cpp

1022

[cor3ntin]

Typo + format

clang/lib/Parse/ParseDeclCXX.cpp

if (Tok.is(tok::r_paren)) {
     Diag(Tok, DiagVal) << getStaticAssertNoMessageFixIt(AssertExpr.get(),
                                                         Tok.getLocation());
   } else {
     if (ExpectAndConsume(tok::comma)) {
       SkipUntil(tok::semi);
       return nullptr;
     }
 
-    if (isTokenStringLiteral())
-      AssertMessage = ParseUnevaluatedStringLiteralExpression();
-    else if (getLangOpts().CPlusPlus26)
+    bool ParseAsExpression = false;
+    if (getLangOpts().CPlusPlus26) {
+      for (unsigned I = 0;; ++I) {
+        const Token &T = GetLookAheadToken(I);
+        if (T.is(tok::r_paren))
+          break;
+        if (T.isNot(tok::string_literal)) {
+          ParseAsExpression = true;
+          break;
+        }
+      }
+    }
+
+    if (ParseAsExpression)
       AssertMessage = ParseConstantExpressionInExprEvalContext();
+    else if (isTokenStringLiteral())
+      AssertMessage = ParseUnevaluatedStringLiteralExpression();
     else {
       Diag(Tok, diag::err_expected_string_literal)
           << /*Source='static_assert'*/ 1;
       SkipMalformedDecl();
       return nullptr;
     }
 
     if (AssertMessage.isInvalid()) {

clang/test/SemaCXX/static-assert-cxx26.cpp

struct string_view {
     constexpr int size() const {
         return S;
     }
     constexpr const char* data() const {
         return D;
     }
 };
 
+constexpr string_view operator+(auto, string_view S) {
+    return S;
+}
+
 constexpr const char g_[] = "long string";
 
 template <typename T, int S>
 struct array {
     constexpr unsigned long size() const {
         return S;
     }
     constexpr const char* data() const {
         return d_;
     }
     const char d_[S];
 };
 
 static_assert(false, string_view("test")); // expected-error {{static assertion failed: test}}
+static_assert(false, "Literal" + string_view("test")); // expected-error {{static assertion failed: test}}
+static_assert(false, L"Wide Literal" + string_view("test")); // expected-error {{static assertion failed: test}}
+static_assert(false, "Wild" "Literal" "Concatenation" + string_view("test")); // expected-error {{static assertion failed: test}}
+static_assert(false, "Wild" "Literal" L"Concatenation" + string_view("test")); // expected-error {{static assertion failed: test}}
+static_assert(false, "Wild" u"Literal" L"Concatenation" + string_view("test")); // expected-error {{unsupported non-standard concatenation of string literals}}
 static_assert(false, string_view("😀")); // expected-error {{static assertion failed: 😀}}
 static_assert(false, string_view(0, nullptr)); // expected-error {{static assertion failed:}}
 static_assert(false, string_view(1, "ABC")); // expected-error {{static assertion failed: A}}
 static_assert(false, string_view(42, "ABC")); // expected-error {{static assertion failed: ABC}} \
                                               // expected-error {{the message in a static assertion must be produced by a constant expression}} \
                                               // expected-note {{read of dereferenced one-past-the-end pointer is not allowed in a constant expression}}
 static_assert(false, array<char, 2>{'a', 'b'}); // expected-error {{static assertion failed: ab}}