[clang][Interp] Don't call getSource() on functions without a body

[tbaeder]

Summary

For builtin functions, we create a Function instance without a body or
code. When emitting diagnostics from them, we need a proper SourceInfo
to point to, but the only thing we can use is the call site of the
builtin function.

[aaron.ballman]

LGTM

clang/lib/AST/Interp/Function.cpp

35

clang/lib/AST/Interp/EvalEmitter.h

protected:
   bool jump(const LabelTy &Label);
   bool fallthrough(const LabelTy &Label);
 
   /// Callback for registering a local.
   Local createLocal(Descriptor *D);
 
   /// Returns the source location of the current opcode.
   SourceInfo getSource(const Function *F, CodePtr PC) const override {
-    return F ? F->getSource(PC) : CurrentSource;
+    return (F && F->hasBody()) ? F->getSource(PC) : CurrentSource;
   }
 
   /// Parameter indices.
   llvm::DenseMap<const ParmVarDecl *, unsigned> Params;
   /// Local descriptors.
   llvm::SmallVector<SmallVector<Local, 8>, 2> Descriptors;
 
 private:

clang/lib/AST/Interp/Function.cpp

Function::ParamDescriptor Function::getParamDescriptor(unsigned Offset) const {
   auto It = Params.find(Offset);
   assert(It != Params.end() && "Invalid parameter offset");
   return It->second;
 }
 
 SourceInfo Function::getSource(CodePtr PC) const {
   assert(PC >= getCodeBegin() && "PC does not belong to this function");
   assert(PC <= getCodeEnd() && "PC Does not belong to this function");
+  assert(hasBody() && "Function has no body");
   unsigned Offset = PC - getCodeBegin();
   using Elem = std::pair<unsigned, SourceInfo>;
   auto It = llvm::lower_bound(SrcMap, Elem{Offset, {}}, llvm::less_first());
   assert(It != SrcMap.end());
   return It->second;
 }
 
 bool Function::isVirtual() const {
   if (auto *M = dyn_cast<CXXMethodDecl>(F))
     return M->isVirtual();
   return false;
 }