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constexpr if condition is not a constant expression and std::is_same #36933

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minib00m mannequin opened this issue May 25, 2018 · 2 comments
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constexpr if condition is not a constant expression and std::is_same #36933

minib00m mannequin opened this issue May 25, 2018 · 2 comments
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bugzilla Issues migrated from bugzilla c++17

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@minib00m
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Mannequin

minib00m mannequin commented May 25, 2018

Bugzilla Link 37585
Resolution FIXED
Resolved on Jul 03, 2018 15:16
Version 6.0
OS Linux

Extended Description

I've found very simple case where clang gives wrong diagnosis.

Let's consider smallest possible program:

#include <type_traits>

int main() {
    if constexpr (std::is_same_v<int, int>) {}
    else if constexpr (std::is_same_v<double, int>) {}
}

clang outputs:

error: constexpr if condition is not a constant expression

    else if constexpr (std::is_same_v<double, int>) {}

Cause of this is statement:
if constexpr (std::is_same_v<int, int>)
any further if constexpr statement is not considered as constant expression.
@llvmbot
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llvmbot commented Jun 19, 2018

I put a patch up here: https://reviews.llvm.org/D48322

@llvmbot
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llvmbot commented Jul 3, 2018

The patch landed as r336233. Thanks for reporting this!

@llvmbot llvmbot transferred this issue from llvm/llvm-bugzilla-archive Dec 10, 2021
This issue was closed.
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