DeclPrinter prints 'final' twice

[kimgr]

@tom-anders @sam-mccall

IWYU's hacky forward-declare printer broke yesterday when 9f57b65 landed.

For the following declaration:

template <typename T>
class FinalTemplate final {};

decl->print() generates:

template <typename T> class final FinalTemplate final {\n}

So while it's nice that final ends up in the right place, it's a little annoying that it's printed both before and after the decl name.

The reason for that is DeclPrinter::prettyPrintAttributes, which emits all decl attributes, and is called before the new final code in DeclPrinter::VisitCXXRecordDecl.

There's a bunch of things wrong with our current parsing and rewriting of the decl->print() output, so I'll look into hardening that, but I figured this might hit someone else.

Not sure why it doesn't show up in your tests. Does the Hover code do any additional cleanup?

[kimgr]

Here's a DeclPrinter unittest that shows the duplication:

diff --git a/clang/unittests/AST/DeclPrinterTest.cpp b/clang/unittests/AST/DeclPrinterTest.cpp
index 11dca6ed6816..79c047edf369 100644
--- a/clang/unittests/AST/DeclPrinterTest.cpp
+++ b/clang/unittests/AST/DeclPrinterTest.cpp
@@ -1324,6 +1324,14 @@ TEST(DeclPrinter, TestTemplateArgumentList15) {
     // Should be: with semicolon
 }
 
+TEST(DeclPrinter, TestTemplateFinal) {
+  ASSERT_TRUE(PrintedDeclCXX11Matches(
+    "template<typename T>"
+    "class FinalTemplate final {};",
+    classTemplateDecl(hasName("FinalTemplate")).bind("id"),
+    "template <typename T> class FinalTemplate final {}"));
+}
+
 TEST(DeclPrinter, TestTemplateArgumentList16) {
   llvm::StringLiteral Code = "template<typename T1, int NT1, typename T2 = "
                              "bool, int NT2 = 5> struct Z {};";

Fails with:

...clang/unittests/AST/DeclPrinterTest.cpp:1328: Failure
Value of: PrintedDeclCXX11Matches( "template<typename T>" "class FinalTemplate final {};", classTemplateDecl(hasName("FinalTemplate")).bind("id"), "template <typename T> class FinalTemplate final {}")
  Actual: false (Expected "template <typename T> class FinalTemplate final {}", got "template <typename T> class final FinalTemplate final {}")

[sam-mccall]

Doh, sorry about that!

Clangd's hover sets PolishForDeclaration, which seems to cause prettyPrintAttributes to not print anything.
This interaction is surprising to me - now I look, PolishForDeclaration does say it hides attributes but I assume it intends to hide things that are syntactically attributes, while final is only semantically one.

I'll fix it and add a test.

[kimgr]

@sam-mccall Thanks! That PolishForDeclaration looks like it would be useful to IWYU as well.