1621789 - Navigation to MatrixType::Simple from reference does not work

Status: RESOLVED FIXED

(Webtools :: Searchfox, defect)

Description

[Botond Ballo [:botond]]

STR

1. Go to https://searchfox.org/mozilla-central/source/gfx/2d/Matrix.h#1955
2. Click on the token Simple token in MatrixType::Simple

Expected results

There is a navigation target that takes you here.

Actual results

There is no such navigation target.

Comment 1

[Botond Ballo [:botond]]

The issue almost certainly has to do with the fact that MatrixType is a nested type defined inside Matrix4x4TypedFlagged which is a template, making it a dependent name. However, the references occur inside the primary template definition, which means they cannot possibly resolve to anything other than the nested type defined inside that same primary template definition.

Comment 2

[Botond Ballo [:botond]]

(In reply to Botond Ballo [:botond] from comment #1)

However, the references occur inside the primary template definition, which means they cannot possibly resolve to anything other than the nested type defined inside that same primary template definition.

I stand corrected: it turns out you can specialize a nested type of a template without specializing the entire template:

template <typename T>
struct Outer {
  enum class MatrixType {
    Simple,   // declaration #1
    NotSimple
  };

  void foo() {
    // MatrixType::Simple resolves to declaration #1
    // unless T = int in which case it resolves to declaration #2
    MatrixType m = MatrixType::Simple;
  }
};

template <>
enum class Outer<int>::MatrixType {
  CPlusPlusFooledYou,
  Simple  // declaration #2
};

int main() {
  Outer<int>().foo();
  Outer<float>().foo();
}

All the same: it would be an eminently reasonable heuristic for Searchfox to resolve the reference to the declaration inside the primary template.

Comment 3

[Andrew Sutherland [:asuth] (he/him)]

Somewhat off-topic here: I think my recent work on the fancy branch with the "structured" record type may let us avoid the general scale-explosion issue with templates that causes us to be so conservative about what we emit.

On trunk, searchfox doesn't really have a concept of a type hierarchy; instead it emits symbols for a method and all of its overrides. This results in scale problems because de-duplication is based on exact match of the JSON record object. With "structured" records, we can instead just say "this is an instantiation of template Foo with T=Bar" and emit the template records as Foo<T>::Method instead of worrying about emitting every method record for every T. I'll try and take a look at whether that's viable this weekend and perhaps file a canonical bug for that with my results.

Comment 4

[Firefox Bug Husbandry Bot]

Because this bug's Severity has not been changed from the default since it was filed, and it's Priority is -- (Backlog,) indicating it has has not been previously triaged, the bug's Severity is being updated to -- (default, untriaged.)

Comment 5

[Firefox Bug Husbandry Bot]

Because this bug's Severity has not been changed from the default since it was filed, and it's Priority is -- (Backlog,) indicating it has has not been previously triaged, the bug's Severity is being updated to -- (default, untriaged.)

Comment 6

[Firefox Bug Husbandry Bot]

Because this bug's Severity has not been changed from the default since it was filed, and it's Priority is -- (Backlog,) indicating it has has not been previously triaged, the bug's Severity is being updated to -- (default, untriaged.)

Comment 7

[Firefox Bug Husbandry Bot]

The severity of these bugs was changed, mistakenly, from normal to S3.

Because these bugs have a priority of --, indicating that they have not been previously triaged, these bugs should be changed to Severity of --.

Comment 9

[Botond Ballo [:botond]]

Reduced testcase:

Steps to reproduce

Have Searchfox index the following code:

template <typename>
struct Foo {
   enum class E {
     Waldo,
   };
   
  void Bar() {
    E::Waldo;
  }
};

Expected results

Navigation from the use of Waldo goes to the definition.

Actual results

No navigation is offered at the use.

Comment 10

[Botond Ballo [:botond]]

The expression type of E::Waldo in the clang AST is DependentScopeDeclRefExpr. That doesn't currently have a Visit method in IndexConsumer; we'll need to add one.

Comment 11

[Botond Ballo [:botond]]

Attachment: Bug 1621789 - Handle DependentScopeDeclRefExpr in MozsearchIndexer. r=asuth

Comment 12

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/24fb0275178b
Handle DependentScopeDeclRefExpr in MozsearchIndexer. r=andi

Comment 13

[Narcis Beleuzu [:NarcisB]]

https://hg.mozilla.org/mozilla-central/rev/24fb0275178b