[analyzer] pr43036: Fix support for operator `sizeof...'.

[NoQ]

Summary

A tiny fix for https://bugs.llvm.org/show_bug.cgi?id=43036 . We should probably double-check other fancy compile-time expressions.

[xazax.hun]

LG!

[a_sidorin]

LGTM++

[Szelethus]

(++LGTM)++

cfe/trunk/lib/StaticAnalyzer/Core/Environment.cpp

SVal Environment::getSVal(const EnvironmentEntry &Entry,
   case Stmt::CXXScalarValueInitExprClass:
   case Stmt::ImplicitValueInitExprClass:
   case Stmt::IntegerLiteralClass:
   case Stmt::ObjCBoolLiteralExprClass:
   case Stmt::CXXNullPtrLiteralExprClass:
   case Stmt::ObjCStringLiteralClass:
   case Stmt::StringLiteralClass:
   case Stmt::TypeTraitExprClass:
+  case Stmt::SizeOfPackExprClass:
     // Known constants; defer to SValBuilder.
     return svalBuilder.getConstantVal(cast<Expr>(S)).getValue();
 
   case Stmt::ReturnStmtClass: {
     const auto *RS = cast<ReturnStmt>(S);
     if (const Expr *RE = RS->getRetValue())
       return getSVal(EnvironmentEntry(RE, LCtx), svalBuilder);
     return UndefinedVal();

cfe/trunk/test/Analysis/sizeofpack.cpp

+// RUN: %clang_analyze_cc1 -analyzer-checker=core,debug.ExprInspection \
+// RUN:                    -verify %s
+
+typedef __typeof(sizeof(int)) size_t;
+
+void clang_analyzer_eval(bool);
+
+template <int... N> size_t foo() {
+  return sizeof...(N);
+}
+
+void bar() {
+  clang_analyzer_eval(foo<>() == 0); // expected-warning{{TRUE}}
+  clang_analyzer_eval(foo<1, 2, 3>() == 3); // expected-warning{{TRUE}}
+}