clang-tidy readability-else-after-return false positive

[LegalizeAdulthood]

Suppose you introduce a variable in the scope of the if statement like so:

    size_t index{};
    if( const auto pos{ std::find( geom->materialIds.begin(), geom->materialIds.end(), proxyMaterialId ) };
        pos == geom->materialIds.end() )
    {
        throw std::runtime_error( "Mismatched material id; expected one of " + toString( geom->materialIds ) + ", got "
                                  + std::to_string( proxyMaterialId ) );
    }
    else
    {
        index = std::distance( geom->materialIds.begin(), pos );
    }

readability-else-after-return doesn't recognize the use of the scoped variable in the else and flags the else after return as a violation. This is a false positive.

[llvmbot]

@llvm/issue-subscribers-bug

Author: Richard Thomson (LegalizeAdulthood)

Suppose you introduce a variable in the scope of the `if` statement like so:

    size_t index{};
    if( const auto pos{ std::find( geom->materialIds.begin(), geom->materialIds.end(), proxyMaterialId ) };
        pos == geom->materialIds.end() )
    {
        throw std::runtime_error( "Mismatched material id; expected one of " + toString( geom->materialIds ) + ", got "
                                  + std::to_string( proxyMaterialId ) );
    }
    else
    {
        index = std::distance( geom->materialIds.begin(), pos );
    }

readability-else-after-return doesn't recognize the use of the scoped variable in the else and flags the else after return as a violation. This is a false positive.

[llvmbot]

@llvm/issue-subscribers-clang-tidy

Author: Richard Thomson (LegalizeAdulthood)

Suppose you introduce a variable in the scope of the `if` statement like so:

    size_t index{};
    if( const auto pos{ std::find( geom->materialIds.begin(), geom->materialIds.end(), proxyMaterialId ) };
        pos == geom->materialIds.end() )
    {
        throw std::runtime_error( "Mismatched material id; expected one of " + toString( geom->materialIds ) + ", got "
                                  + std::to_string( proxyMaterialId ) );
    }
    else
    {
        index = std::distance( geom->materialIds.begin(), pos );
    }

readability-else-after-return doesn't recognize the use of the scoped variable in the else and flags the else after return as a violation. This is a false positive.

[chrchr-github]

Reduced/compilable:

#include <cstdlib>

int main() {
    int i{};
    if (int x = rand(); x == 0) {
        throw 0;
    }
    else {
        i = x;
    }
    return i;
}

https://godbolt.org/z/oPbWxaEdK

To be fair, it is possible to rewrite this without else after return:

int main() {
    int i{};
    {
        int x = rand();
        if (x == 0) {
            throw 0;
        i = x;
    }
    return i;
}