[NFC][Clang] Fix static analyzer concerns

[eandrews]

Summary

Fix static analyzer concerns about dereferencing null values

[aaron.ballman]

LGTM though there may be some additional changes worth considering; I don't insist on changes though.

clang/lib/AST/StmtPrinter.cpp

178

Hmmm, I think this is what we're effectively already hoping is the case today, but I don't think that's a safe assertion by itself. Consider: https://github.com/llvm/llvm-project/blob/cd29ebb862b5c7a81c9f39c8c493f9246d6e5f0b/clang/lib/AST/StmtPrinter.cpp#L602

It might be worth looking at all the calls to PrintRawCompoundStmt() to see which ones potentially can pass null in, and decide if there are additional changes to make. e.g., should that dyn_cast be a cast instead so it cannot return nullptr and we get the assertion a little bit earlier when calling cast<>?

[tahonermann]

I think this change is good as is, but I added some additional thoughts to Aaron's earlier comment.

clang/lib/AST/StmtPrinter.cpp

178

Another possibility would be to modify ObjCAtFinallyStmt to declare AtFinallyStmt as CompoundStmt* and to modify getFinallyBody() and setFinallyBody() accordingly. That would remove the need for that dyn_cast in StmtPrinter::VisitObjCAtTryStmt(). This would then require additional changes such as updates to ASTStmtReader::VisitObjCAtFinallyStmt() to perform a cast as is done in ASTStmtReader::VisitStmtExpr(). But none of that actually addresses the fact that this function has a precondition that Node is not null.

[eandrews]

Changed a dyn_cast to cast and handled ObjCAtFinallyStmt similar to how ObjCAtTryStmt is handled, i.e. just check that it exists before calling PrintRawCompoundStmt

clang/lib/AST/StmtPrinter.cpp

 
 //===----------------------------------------------------------------------===//
 //  Stmt printing methods.
 //===----------------------------------------------------------------------===//
 
 /// PrintRawCompoundStmt - Print a compound stmt without indenting the {, and
 /// with no newline after the }.
 void StmtPrinter::PrintRawCompoundStmt(CompoundStmt *Node) {
+  assert(Node && "Compound statement cannot be null");
   OS << "{" << NL;
   PrintFPPragmas(Node);
   for (auto *I : Node->body())
     PrintStmt(I);
 
   Indent() << "}";
 }
 

clang/lib/Analysis/PathDiagnostic.cpp

PathDiagnosticLocation::createBegin(const Decl *D,
                                     const SourceManager &SM) {
   return PathDiagnosticLocation(D->getBeginLoc(), SM, SingleLocK);
 }
 
 PathDiagnosticLocation
 PathDiagnosticLocation::createBegin(const Stmt *S,
                                     const SourceManager &SM,
                                     LocationOrAnalysisDeclContext LAC) {
+  assert(S && "Statement cannot be null");
   return PathDiagnosticLocation(getValidSourceLocation(S, LAC),
                                 SM, SingleLocK);
 }
 
 PathDiagnosticLocation
 PathDiagnosticLocation::createEnd(const Stmt *S,
                                   const SourceManager &SM,
                                   LocationOrAnalysisDeclContext LAC) {