EDG __builtin_is_implicit_lifetime isn't checking for trivial constructors

[StephanTLavavej]

Issue Summary

I'm the primary maintainer of microsoft/STL, and we've encountered a bug in EDG, which we're working around in the STL. Using VS Insiders / MSVC Build Tools Preview, the following code is correctly accepted by the MSVC Compiler 19.52.36815 and Clang 22.1.3, but incorrectly rejected by EDG 6.9. This is using MSVC's undocumented /BE option to invoke VS's copy of the EDG frontend used for IntelliSense.

When we reported this to EDG before it was open-sourced, we were told this was being tracked as EDGcpfe/28805. (For my own reference, this was also MSVC-internal VSO-2941370.)

Reproducing Source Code

class NonAggregate {
public:
    NonAggregate() = default;

    NonAggregate(const NonAggregate&)            = delete;
    NonAggregate& operator=(const NonAggregate&) = delete;

    void set_num(int x) {
        num = x;
    }
    int get_num() const {
        return num;
    }

private:
    int num;
};

class DataMemberInitializer {
public:
    DataMemberInitializer() = default;

    DataMemberInitializer(const DataMemberInitializer&)            = delete;
    DataMemberInitializer& operator=(const DataMemberInitializer&) = delete;

    void set_num(int x) {
        num = x;
    }
    int get_num() const {
        return num;
    }

private:
    int num{0};
};

class UserProvidedConstructor {
public:
    UserProvidedConstructor() {}

    UserProvidedConstructor(const UserProvidedConstructor&)            = delete;
    UserProvidedConstructor& operator=(const UserProvidedConstructor&) = delete;

    void set_num(int x) {
        num = x;
    }
    int get_num() const {
        return num;
    }

private:
    int num;
};

// N5014 [dcl.init.aggr]/1.2:
// "An aggregate is an array or a class (Clause 11) with [...]
// no private or protected direct non-static data members (11.8),"

// N5014 [class.default.ctor]/3:
// "A default constructor for a class X is trivial if it is not user-provided and if [...]
// - no non-static data member of X has a default member initializer (11.4), and [...]
// Otherwise, the default constructor is non-trivial."

// N5014 [class.prop]/16:
// "A class S is an implicit-lifetime class if
// - it is an aggregate whose destructor is not user-provided or
// - it has at least one trivial eligible constructor and a trivial, non-deleted destructor."

static_assert(__builtin_is_implicit_lifetime(NonAggregate));
static_assert(!__builtin_is_implicit_lifetime(DataMemberInitializer));
static_assert(!__builtin_is_implicit_lifetime(UserProvidedConstructor));

Command-line Options

cl /EHsc /nologo /W4 /std:c++latest /c /BE /dE--version meow.cpp

Type of Issue

[Front End] This code SHOULD compile with these options.

Additional Details

Compiler output showing how MSVC and Clang accept while EDG rejects:

C:\Temp>cl
Microsoft (R) C/C++ Optimizing Compiler Version 19.52.36815 for x64 (PREVIEW)
Copyright (C) Microsoft Corporation.  All rights reserved.

usage: cl [ option... ] filename... [ /link linkoption... ]

C:\Temp>cl /EHsc /nologo /W4 /std:c++latest /c meow.cpp
meow.cpp

C:\Temp>clang-cl -v
clang version 22.1.3 (https://github.com/llvm/llvm-project e9846648fd6183ee6d8cbdb4502213fcf902a211)
Target: x86_64-pc-windows-msvc
Thread model: posix
InstalledDir: C:\Program Files\Microsoft Visual Studio\18\Insiders\VC\Tools\Llvm\x64\bin

C:\Temp>clang-cl /EHsc /nologo /W4 /std:c++latest /c meow.cpp

C:\Temp>cl /EHsc /nologo /W4 /std:c++latest /c /BE /dE--version meow.cpp
meow.cpp
Edison Design Group C/C++ Front End, version 6.9 (Sep 15 2026 13:46:37)
Copyright 1988-2026 Edison Design Group, Inc.

"meow.cpp", line 70: error: static assertion failed
  static_assert(!__builtin_is_implicit_lifetime(DataMemberInitializer));
  ^

"meow.cpp", line 71: error: static assertion failed
  static_assert(!__builtin_is_implicit_lifetime(UserProvidedConstructor));
  ^

Reproducing (Standard) Configuration(s)

windows-msvc-release

Reproducing (Non-standard) Configuration

dump_configuration.txt

I acknowledge that:

• I have checked open issues and existing discussions before filing this report.
• The reproducing source code that I have provided does not depend on headers that I have not included with my submission.
• I have reduced the reproducing source code to the best of my ability.
• I have selected at least one standard configuration or uploaded a non-standard configuration dump.
• I understand code shared via this form is NOT confidential.
• I have permission to share the reproducing source code and grant permission for the project to use the source code (or derivatives of the source code) to create tests.
• I agree that any tests created using the reproducing source code (or deriatives of it) will be licensed under project license unless I included a LICENSE.txt file in my .zip or .tar.gz upload. If I included a LICENSE.txt file, any tests created using the reproducing source code will be governed by the terms of the license I provided instead.