[ASTDump] Mark null params with a tag rather than a child node

[aaron.ballman]

Do we have any test coverage for this change? IIRC, this was one we couldn't figure out how to trigger?

lib/AST/ASTDumper.cpp

637

Extra whitespace at the start of the string literal, or is that intentional? Also, do we want to standardize on <<<NULL>>> with three brackets instead of two?

647–648

You can drop getNumParams() here -- if param_begin() returns a non-null value, getNumParams() must return a non-zero value.

(param_begin() is implemented in terms of parameters(), which calls getNumParams() when setting up the returned ArrayRef.)

[aaron.ballman]

lib/AST/ASTDumper.cpp

637

Ah, I understand the whitespace now, so that was intentional I believe. Question remains about whether we want to also switch to use <<< consistently remains though.

[aaron.ballman]

lib/AST/ASTDumper.cpp

647–648

It seems that this is needed because the situation can arise when the function is not fully constructed yet, such as when calling dump() under the debugger.

I think this can be more clearly expressed as if (!D->param_empty() && !D->param_begin()), but should also have some comments explaining that this is guarding against a situation that only comes up while debugging, and thus is not covered by any existing test cases.

[steveire]

Update

[aaron.ballman]

With bracket and comment changes, LGTM. No need for tests on this one because the scenario changed can only occur during debugging.

lib/AST/ASTDumper.cpp

636

Re-flow comments to 80-col.

642

Let's make this <<<NULL params x blah>>> with three brackets instead of two.

lib/AST/ASTDumper.cpp

if (MD->size_overridden_methods() != 0) {
           OS << ", ";
           dumpOverride(Override);
         }
         OS << " ]";
       });
     }
   }
 
+  // Since NumParams comes from the FunctionProtoType of the
+  // FunctionDecl and the Params are set later, it is possible
+  // for a dump during debugging to encounter a FunctionDecl
+  // that has been created but hasn't been assigned
+  // ParmVarDecls yet.
+  if (!D->param_empty() && !D->param_begin())
+    OS << " <<NULL params x " << D->getNumParams() << ">>";
+
   if (const auto *FTSI = D->getTemplateSpecializationInfo())
     dumpTemplateArgumentList(*FTSI->TemplateArguments);
 
-  if (!D->param_begin() && D->getNumParams())
-    dumpChild([=] { OS << "<<NULL params x " << D->getNumParams() << ">>"; });
-  else
-    for (const ParmVarDecl *Parameter : D->parameters())
+  if (D->param_begin())
+    for (const auto *Parameter : D->parameters())
       dumpDecl(Parameter);
 
   if (const auto *C = dyn_cast<CXXConstructorDecl>(D))
     for (const auto *I : C->inits())
       dumpCXXCtorInitializer(I);
 
   if (D->doesThisDeclarationHaveABody())
     dumpStmt(D->getBody());