[analyzer] Avoid querying this-pointers for static-methods.

[mattd]

Summary

The loop-widening code processes c++ methods looking for this pointers. In
the case of static methods (which do not have this pointers), an assertion
was triggering. This patch avoids trying to process this pointers for
static methods, and thus avoids triggering the assertion .

[george.karpenkov]

Looks reasonable. @NoQ any further comments?

[NoQ]

Yup, fair enough.

lib/StaticAnalyzer/Core/LoopWidening.cpp

for (BoundNodes Match : Matches) {
     const VarRegion *VarMem = MRMgr.getVarRegion(VD, LCtx);
     ITraits.setTrait(VarMem,
                      RegionAndSymbolInvalidationTraits::TK_PreserveContents);
   }
 
 
   // 'this' pointer is not an lvalue, we should not invalidate it. If the loop
   // is located in a method, constructor or destructor, the value of 'this'
-  // pointer shoule remain unchanged.
-  if (const CXXMethodDecl *CXXMD = dyn_cast<CXXMethodDecl>(STC->getDecl())) {
+  // pointer should remain unchanged.  Ignore static methods, since they do not
+  // have 'this' pointers.
+  const CXXMethodDecl *CXXMD = dyn_cast<CXXMethodDecl>(STC->getDecl());
+  if (CXXMD && !CXXMD->isStatic()) {
     const CXXThisRegion *ThisR = MRMgr.getCXXThisRegion(
         CXXMD->getThisType(STC->getAnalysisDeclContext()->getASTContext()),
         STC);
     ITraits.setTrait(ThisR,
                      RegionAndSymbolInvalidationTraits::TK_PreserveContents);
   }
 
   return PrevState->invalidateRegions(Regions, getLoopCondition(LoopStmt),
                                       BlockCount, LCtx, true, nullptr, nullptr,
                                       &ITraits);
 }
 
 } // end namespace ento
 } // end namespace clang

test/Analysis/loop-widening-ignore-static-methods.cpp

+// RUN: %clang_analyze_cc1 -analyzer-checker=core -analyzer-config widen-loops=true -analyzer-max-loop 2 %s
+// REQUIRES: asserts
+// expected-no-diagnostics
+//
+// This test checks that the loop-widening code ignores static methods.  If that is not the
+// case, then an assertion will trigger.
+
+class Test {
+  static void foo() {
+    for (;;) {}
+  }
+};