[clang] Give priority to Class context while parsing declarations

[furkanusta]

Summary

Fixes: https://github.com/clangd/clangd/issues/290

[kadircet]

Can you also add a test, preferably in clang/test/CodeCompletion/overrides.cpp ?

clang/lib/Parse/ParseDecl.cpp

3269–3270

i think the importance of ordering requires a comment here, maybe something like:
Class context can appear inside a function/block, so prioritise that.

[furkanusta]

• [clang] Add test case for D130363

[furkanusta]

I've added a test case but I have a question.
This is regardless of the current issue (i.e. no function context, clang++14 with no patches)

struct X {
virtual void foo();
};
struct Y : public X {
over
};

I am trying to complete override in class Y here, but I get no result.
The command I am using is:
clang++ -cc1 -xc++ -code-completion-patterns -fsyntax-only -code-completion-at="test.cpp:5:2" test.cpp
The only output I get is: COMPLETION: operator
If I start the completion at the first column I receive the correct result.
Is my invocation correct or is this case handled by clangd and not clang?

[kadircet]

Is my invocation correct or is this case handled by clangd and not clang?

yeah your invocation is correct. this is because clang's printer does a prefix based filtering (while clangd does a fuzzy match) https://github.com/llvm/llvm-project/blob/main/clang/lib/Sema/CodeCompleteConsumer.cpp#L623.

clang/test/CodeCompletion/overrides.cpp

36

no need for -code-completion-patterns. can you also move the new test case below (after CHECK-CC3-NOT) that way we get to keep the line numbers for old tests the same.

[furkanusta]

• [clangd] D130363 (CodeCompletion/overrides.cpp) Move tests to bottom

[kadircet]

thanks, lgtm! let me know if i should land this for you.

[furkanusta]

That would be great, thanks

clang/test/CodeCompletion/overrides.cpp

36

I put the test in between because anything after vf on line 14 gives an error.

error: unknown type name 'vf'

vf
^

It still outputs the correct completions but since the return code is non-zero, FileCheck fails

36

I've found from one of the others tests it is possible to invert the return code from clang.
This way I was able to move the newly added test to bottom.

clang/lib/Parse/ParseDecl.cpp

case tok::code_completion: {
 
         cutOffParsing();
         Actions.CodeCompleteDeclSpec(getCurScope(), DS,
                                      AllowNonIdentifiers,
                                      AllowNestedNameSpecifiers);
         return;
       }
 
-      if (getCurScope()->getFnParent() || getCurScope()->getBlockParent())
-        CCC = Sema::PCC_LocalDeclarationSpecifiers;
-      else if (TemplateInfo.Kind != ParsedTemplateInfo::NonTemplate)
+      // Class context can appear inside a function/block, so prioritise that.
+      if (TemplateInfo.Kind != ParsedTemplateInfo::NonTemplate)
         CCC = DSContext == DeclSpecContext::DSC_class ? Sema::PCC_MemberTemplate
                                                       : Sema::PCC_Template;
       else if (DSContext == DeclSpecContext::DSC_class)
         CCC = Sema::PCC_Class;
+      else if (getCurScope()->getFnParent() || getCurScope()->getBlockParent())
+        CCC = Sema::PCC_LocalDeclarationSpecifiers;
       else if (CurParsedObjCImpl)
         CCC = Sema::PCC_ObjCImplementation;
 
       cutOffParsing();
       Actions.CodeCompleteOrdinaryName(getCurScope(), CCC);
       return;
     }
 

clang/test/CodeCompletion/overrides.cpp

 class A {
  public:
   virtual void vfunc(bool param);
   virtual void vfunc(bool param, int p);
   void func(bool param);
 };
 class B : public A {
 virtual int ttt(bool param, int x = 3) const;
 void vfunc(bool param, int p) override;
 };
 class C : public B {
  public:
   void vfunc(bool param) override;
-  vf
+  vf;
 };
 
 // Runs completion at ^vf
 // RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:14:3 %s -o - | FileCheck -check-prefix=CHECK-CC1 %s
 // CHECK-CC1: COMPLETION: Pattern : int ttt(bool param, int x = 3) const override{{$}}
 // CHECK-CC1: COMPLETION: Pattern : void vfunc(bool param, int p) override{{$}}
 // CHECK-CC1-NOT: COMPLETION: Pattern : void vfunc(bool param) override{{$}}
 //
 // Runs completion at vf^
 // RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:14:5 %s -o - | FileCheck -check-prefix=CHECK-CC2 %s
 // CHECK-CC2-NOT: COMPLETION: Pattern : int ttt(bool param, int x = 3) const override{{$}}
 // CHECK-CC2: COMPLETION: Pattern : void vfunc(bool param, int p) override{{$}}
 // CHECK-CC2-NOT: COMPLETION: Pattern : void vfunc(bool param) override{{$}}
 //
 // Runs completion at void ^ on line 13.
 // RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:13:8 %s -o - | FileCheck -check-prefix=CHECK-CC3 %s
 // CHECK-CC3-NOT: COMPLETION: Pattern : int ttt(bool param, int x = 3) const override{{$}}
 // CHECK-CC3-NOT: COMPLETION: Pattern : void vfunc(bool param, int p) override{{$}}
 // CHECK-CC3-NOT: COMPLETION: Pattern : void vfunc(bool param) override{{$}}
+
+void func() {
+  class D : public A {
+
+  };
+}
+
+// Runs completion at empty line on line 37.
+// RUN: not %clang_cc1 -fsyntax-only -code-completion-at=%s:37:1 %s -o - | FileCheck -check-prefix=CHECK-CC4 %s
+// CHECK-CC4: COMPLETION: Pattern : void vfunc(bool param, int p) override{{$}}