Assertion in form_exception_specification_for_generated_function

[dgrunwald-qt]

Issue Summary

Due to unexpected reentrancy in complete_defaulted_exc_spec, an assertion can occur in form_exception_specification_for_generated_function.

Reproducing Source Code

struct Outer {
    struct Inner {
        Inner() = default;
        int x = 42;
    };
    Inner inner = noexcept(Inner()) ? Inner() : Inner();
    static constexpr bool inner_is_noexcept = noexcept(Inner());
};
Outer o;

https://godbolt.org/z/565T1Wfoq

Command-line Options

cpfe --c++17

Type of Issue

[Front End] I do not care but this code CRASHES the compiler.

Additional Details

This reproducer is rejected by gcc-16, accepted by gcc-trunk, and crashes the EDG frontend.

"test.cpp", line 7: internal error: assertion failed at: "class_decl.c", line
          13764 in form_exception_specification_for_generated_function

      static constexpr bool inner_is_noexcept = noexcept(Inner());
                                                         ^

Reproducing (Standard) Configuration(s)

linux-gcc-debug

Reproducing (Non-standard) Configuration

No response

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• 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.
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