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during the lookup for a base class name, non-type names should be ignored #16855

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llvmbot opened this issue Jun 28, 2013 · 2 comments · Fixed by #112166
Closed

during the lookup for a base class name, non-type names should be ignored #16855

llvmbot opened this issue Jun 28, 2013 · 2 comments · Fixed by #112166
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bugzilla Issues migrated from bugzilla c++ clang:frontend Language frontend issues, e.g. anything involving "Sema"

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@llvmbot
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llvmbot commented Jun 28, 2013 •
edited by shafik
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Bugzilla Link 16481
Version 3.2
OS Windows NT
Reporter LLVM Bugzilla Contributor
CC @DougGregor

Extended Description

[class.derived]p2 says:

"During the lookup for a base class name, non-type names are ignored."

So clang should compile this program:

struct x
{};

namespace
{
    namespace x
    {
        struct y : x
        {};
    }
}
@llvmbot llvmbot transferred this issue from llvm/llvm-bugzilla-archive Dec 9, 2021
@Endilll Endilll added the clang:frontend Language frontend issues, e.g. anything involving "Sema" label Nov 3, 2023
@llvmbot
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llvmbot commented Nov 3, 2023

@llvm/issue-subscribers-clang-frontend

Author: None (llvmbot)

| | | | --- | --- | | Bugzilla Link | [16481](https://llvm.org/bz16481) | | Version | 3.2 | | OS | Windows NT | | Reporter | LLVM Bugzilla Contributor | | CC | @DougGregor |

Extended Description

[class.derived]p2 says:

"During the lookup for a base class name, non-type names are ignored."

So clang should compile this program:

struct x
{};

namespace
{
namespace x
{
struct y : x
{};
}
}

@shafik
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shafik commented Nov 4, 2023 •
edited
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It looks like we have a FIXME for this:

llvm-project/clang/lib/Sema/SemaDecl.cpp

Lines 402 to 406 in b0d5b4d

// FIXME: LookupNestedNameSpecifierName isn't the right kind of
// lookup for class-names.
LookupNameKind Kind = isClassName ? LookupNestedNameSpecifierName :
LookupOrdinaryName;
LookupResult Result(*this, &II, NameLoc, Kind);

from 9025ec2

CC @zygoloid who might know of how to fix this correctly

Note:

During the lookup for a base class name, non-type names are ignored.

is not in the standard anymore but it is not clear what replaced it.

@shafik shafik mentioned this issue Feb 14, 2024
Open
spaits added a commit to spaits/llvm-project that referenced this issue Oct 14, 2024
@spaits
Use tag name lookup for class names
e9d43ef 
This PR would fix llvm#16855 .

I think the correct lookup to use for class names is Tag name lookup,
because it does not take namespaces into account. The current lookup
does and because of this some valid programs are not accepted.

If you think that Tag name lookup is not correct for all cases when
we are looking up types based on class names then we can only
do tag name lookup when looking up class names for inheritance.
In case of inheritance:
```
[class.derived]p2 says:

"During the lookup for a base class name, non-type names are ignored."
```
@spaits spaits mentioned this issue Oct 14, 2024
Merged
spaits added a commit to spaits/llvm-project that referenced this issue Oct 14, 2024
@spaits
Use tag name lookup for class names
64aa2ad 
This PR would fix llvm#16855 .

I think the correct lookup to use for class names is Tag name lookup,
because it does not take namespaces into account. The current lookup
does and because of this some valid programs are not accepted.

If you think that Tag name lookup is not correct for all cases when
we are looking up types based on class names then we can only
do tag name lookup when looking up class names for inheritance.
In case of inheritance:
```
[class.derived]p2 says:

"During the lookup for a base class name, non-type names are ignored."
```
spaits added a commit to spaits/llvm-project that referenced this issue Oct 14, 2024
@spaits
Use tag name lookup for class names
6935e90 
This PR would fix llvm#16855 .

I think the correct lookup to use for class names is Tag name lookup,
because it does not take namespaces into account. The current lookup
does and because of this some valid programs are not accepted.

If you think that Tag name lookup is not correct for all cases when
we are looking up types based on class names then we can only
do tag name lookup when looking up class names for inheritance.
In case of inheritance:
```
[class.derived]p2 says:

"During the lookup for a base class name, non-type names are ignored."
```
spaits added a commit to spaits/llvm-project that referenced this issue Oct 15, 2024
@spaits
Use tag name lookup for class names
4afa9c5 
This PR would fix llvm#16855 .

I think the correct lookup to use for class names is Tag name lookup,
because it does not take namespaces into account. The current lookup
does and because of this some valid programs are not accepted.

If you think that Tag name lookup is not correct for all cases when
we are looking up types based on class names then we can only
do tag name lookup when looking up class names for inheritance.
In case of inheritance:
```
[class.derived]p2 says:

"During the lookup for a base class name, non-type names are ignored."
```
@spaits spaits closed this as completed in 4852120 Oct 15, 2024
DanielCChen pushed a commit to DanielCChen/llvm-project that referenced this issue Oct 16, 2024
@spaits @DanielCChen
[Sema]Use tag name lookup for class names (llvm#112166)
4f63e44 
This PR would fix llvm#16855 .

The correct lookup to use for class names is Tag name lookup,
because it does not take namespaces into account. The lookup before
does and because of this some valid programs are not accepted.

An example scenario of a valid program being declined is when you have a struct (let's call it `y`) inheriting from another struct with a name `x` but the struct `y` is in a namespace that is also called `x`:
```
struct x
{};

namespace
{
    namespace x
    {
        struct y : x
        {};
    }
}
```

This shall be accepted because: 
```
C++ [class.derived]p2 (wrt lookup in a base-specifier): The lookup for
  // the component name of the type-name or simple-template-id is type-only.
```
bricknerb pushed a commit to bricknerb/llvm-project that referenced this issue Oct 17, 2024
@spaits @bricknerb
[Sema]Use tag name lookup for class names (llvm#112166)
bd03c48 
This PR would fix llvm#16855 .

The correct lookup to use for class names is Tag name lookup,
because it does not take namespaces into account. The lookup before
does and because of this some valid programs are not accepted.

An example scenario of a valid program being declined is when you have a struct (let's call it `y`) inheriting from another struct with a name `x` but the struct `y` is in a namespace that is also called `x`:
```
struct x
{};

namespace
{
    namespace x
    {
        struct y : x
        {};
    }
}
```

This shall be accepted because: 
```
C++ [class.derived]p2 (wrt lookup in a base-specifier): The lookup for
  // the component name of the type-name or simple-template-id is type-only.
```
EricWF pushed a commit to efcs/llvm-project that referenced this issue Oct 22, 2024
@spaits @EricWF
[Sema]Use tag name lookup for class names (llvm#112166)
bf7d610 
This PR would fix llvm#16855 .

The correct lookup to use for class names is Tag name lookup,
because it does not take namespaces into account. The lookup before
does and because of this some valid programs are not accepted.

An example scenario of a valid program being declined is when you have a struct (let's call it `y`) inheriting from another struct with a name `x` but the struct `y` is in a namespace that is also called `x`:
```
struct x
{};

namespace
{
    namespace x
    {
        struct y : x
        {};
    }
}
```

This shall be accepted because: 
```
C++ [class.derived]p2 (wrt lookup in a base-specifier): The lookup for
  // the component name of the type-name or simple-template-id is type-only.
```
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[Sema]Use tag name lookup for class names spaits/llvm-project
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@shafik @Endilll @llvmbot