PR23942: a pure-specifier's integer literal must be spelled '0'

llvm-svn: 241019
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index ae97b24..bce0a37 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -8783,6 +8783,19 @@
   }
 }
 
+/// Determine whether the given expression was formed from the token '0'. This
+/// test is necessary to determine whether an initializer is really a
+/// pure-specifier.
+static bool isZeroToken(Sema &S, Expr *E) {
+  auto *IL = dyn_cast<IntegerLiteral>(E);
+  if (!IL || !!IL->getValue() ||
+      !IL->getType()->isSpecificBuiltinType(BuiltinType::Int))
+    return false;
+
+  SmallString<8> Buffer;
+  return S.PP.getSpelling(E->getLocStart(), Buffer) == "0";
+}
+
 /// AddInitializerToDecl - Adds the initializer Init to the
 /// declaration dcl. If DirectInit is true, this is C++ direct
 /// initialization rather than copy initialization.
@@ -8799,9 +8812,11 @@
     // With declarators parsed the way they are, the parser cannot
     // distinguish between a normal initializer and a pure-specifier.
     // Thus this grotesque test.
-    IntegerLiteral *IL;
-    if ((IL = dyn_cast<IntegerLiteral>(Init)) && IL->getValue() == 0 &&
-        Context.getCanonicalType(IL->getType()) == Context.IntTy)
+    //
+    // FIXME: The parser should instead treat anything that looks like a
+    // pure-specifier as a pure-specifier, and Sema should convert it to an
+    // initializer when necessary, rather than doing things this way around.
+    if (!DirectInit && isZeroToken(*this, Init))
       CheckPureMethod(Method, Init->getSourceRange());
     else {
       Diag(Method->getLocation(), diag::err_member_function_initialization)