[OPENMP] Fix crash in LoopCounterRefChecker when MemberExpr is not Var or Field

[mikerice]

Summary

checkDecl is only valid for VarDecls or FieldDecls, since getCanonicalDecl expects only these. Prevent other Decl kinds (such as CXXMethodDecls and EnumConstantDecls) from entering and asserting.

[ABataev]

LG

clang/lib/Sema/SemaOpenMP.cpp

bool VisitDeclRefExpr(const DeclRefExpr *E) {
     const ValueDecl *VD = E->getDecl();
     if (isa<VarDecl>(VD))
       return checkDecl(E, VD);
     return false;
   }
   bool VisitMemberExpr(const MemberExpr *E) {
     if (isa<CXXThisExpr>(E->getBase()->IgnoreParens())) {
       const ValueDecl *VD = E->getMemberDecl();
+      if (isa<VarDecl>(VD) || isa<FieldDecl>(VD))
         return checkDecl(E, VD);
     }
     return false;
   }
   bool VisitStmt(const Stmt *S) {
     bool Res = true;
     for (const Stmt *Child : S->children())
       Res = Child && Visit(Child) && Res;
     return Res;

clang/test/OpenMP/for_loop_messages.cpp

for (GoodIter1 I = I1; I < E1; I++)
     ;
   return 0;
 }
 
 template <typename IT, int ST>
 class TC {
   int ii, iii, kk;
 public:
+  enum { myconstant = 42 };
+  int ub();
   int dotest_lt(IT begin, IT end) {
 #pragma omp parallel
 // expected-error@+3 3 {{the loop initializer expression depends on the current loop control variable}}
 // expected-error@+2 6 {{the loop condition expression depends on the current loop control variable}}
 #pragma omp for
   for (ii = ii * 10 + 25; ii < ii / ii - 23; ii += 1)
     ;
 
+// Check that member function calls and enum constants in the condition is
+// handled.
+#pragma omp for
+  for (ii = 0; ii < ub() + this->myconstant; ii += 1) // expected-no-error
+    ;
+
 #pragma omp parallel
 // expected-error@+4 2 {{expected loop invariant expression or '<invariant1> * ii + <invariant2>' kind of expression}}
 // expected-error@+3 {{expected loop invariant expression or '<invariant1> * TC::ii + <invariant2>' kind of expression}}
 #pragma omp for collapse(2)
     for (ii = 10 + 25; ii < 1000; ii += 1)
       for (iii = ii * 10 + 25; iii < ii / ii - 23; iii += 1)
         ;