https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101194
Bug ID: 101194 Summary: 7.2 Regression Product: gcc Version: 7.2.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: yannick.lepennec+gcc at live dot fr Target Milestone: --- Dear Maintainers, Obligatory godbolt: https://godbolt.org/z/KnMnc7P57 Since GCC 7.2: $ g++ -std=c++17 -Wall -Wextra -pedantic-errors #include <array> struct nodefault { nodefault(int) {} }; int main() { std::array<nodefault, 1> arr1{ nodefault{1} }; // OK std::array<nodefault, 1> arr2{ arr1[0] }; // Error??? } Gives: main.cpp: In function 'int main()': main.cpp:9:44: error: no matching function for call to 'nodefault::nodefault()' std::array<nodefault, 1> arr2{ arr1[0] }; // Error??? ^ main.cpp:4:5: note: candidate: nodefault::nodefault(int) nodefault(int) {} ^~~~~~~~~ main.cpp:4:5: note: candidate expects 1 argument, 0 provided main.cpp:3:8: note: candidate: constexpr nodefault::nodefault(const nodefault&) struct nodefault { ^~~~~~~~~ main.cpp:3:8: note: candidate expects 1 argument, 0 provided main.cpp:3:8: note: candidate: constexpr nodefault::nodefault(nodefault&&) main.cpp:3:8: note: candidate expects 1 argument, 0 provided main.cpp:9:44: error: no matching function for call to 'nodefault::nodefault()' std::array<nodefault, 1> arr2{ arr1[0] }; // Error??? ^ main.cpp:4:5: note: candidate: nodefault::nodefault(int) nodefault(int) {} ^~~~~~~~~ main.cpp:4:5: note: candidate expects 1 argument, 0 provided main.cpp:3:8: note: candidate: constexpr nodefault::nodefault(const nodefault&) struct nodefault { ^~~~~~~~~ main.cpp:3:8: note: candidate expects 1 argument, 0 provided main.cpp:3:8: note: candidate: constexpr nodefault::nodefault(nodefault&&) main.cpp:3:8: note: candidate expects 1 argument, 0 provided main.cpp:9:44: error: no matching function for call to 'nodefault::nodefault()' std::array<nodefault, 1> arr2{ arr1[0] }; // Error??? ^ main.cpp:4:5: note: candidate: nodefault::nodefault(int) nodefault(int) {} ^~~~~~~~~ main.cpp:4:5: note: candidate expects 1 argument, 0 provided main.cpp:3:8: note: candidate: constexpr nodefault::nodefault(const nodefault&) struct nodefault { ^~~~~~~~~ main.cpp:3:8: note: candidate expects 1 argument, 0 provided main.cpp:3:8: note: candidate: constexpr nodefault::nodefault(nodefault&&) main.cpp:3:8: note: candidate expects 1 argument, 0 provided main.cpp:9:44: error: no matching function for call to 'nodefault::nodefault()' std::array<nodefault, 1> arr2{ arr1[0] }; // Error??? ^ main.cpp:4:5: note: candidate: nodefault::nodefault(int) nodefault(int) {} ^~~~~~~~~ main.cpp:4:5: note: candidate expects 1 argument, 0 provided main.cpp:3:8: note: candidate: constexpr nodefault::nodefault(const nodefault&) struct nodefault { ^~~~~~~~~ main.cpp:3:8: note: candidate expects 1 argument, 0 provided main.cpp:3:8: note: candidate: constexpr nodefault::nodefault(nodefault&&) main.cpp:3:8: note: candidate expects 1 argument, 0 provided main.cpp:9:44: error: no matching function for call to 'nodefault::nodefault()' std::array<nodefault, 1> arr2{ arr1[0] }; // Error??? ^ main.cpp:4:5: note: candidate: nodefault::nodefault(int) nodefault(int) {} ^~~~~~~~~ main.cpp:4:5: note: candidate expects 1 argument, 0 provided main.cpp:3:8: note: candidate: constexpr nodefault::nodefault(const nodefault&) struct nodefault { ^~~~~~~~~ main.cpp:3:8: note: candidate expects 1 argument, 0 provided main.cpp:3:8: note: candidate: constexpr nodefault::nodefault(nodefault&&) main.cpp:3:8: note: candidate expects 1 argument, 0 provided main.cpp:9:44: error: no matching function for call to 'nodefault::nodefault()' std::array<nodefault, 1> arr2{ arr1[0] }; // Error??? ^ main.cpp:4:5: note: candidate: nodefault::nodefault(int) nodefault(int) {} ^~~~~~~~~ main.cpp:4:5: note: candidate expects 1 argument, 0 provided main.cpp:3:8: note: candidate: constexpr nodefault::nodefault(const nodefault&) struct nodefault { ^~~~~~~~~ main.cpp:3:8: note: candidate expects 1 argument, 0 provided main.cpp:3:8: note: candidate: constexpr nodefault::nodefault(nodefault&&) main.cpp:3:8: note: candidate expects 1 argument, 0 provided --- GCC 7.2 and above accept the same code with -std=c++14. GCC 7.1 accepts it with either. The error message seems to have gotten shorter in more recent GCC, but is still present. I have bisected this to https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=0634d9fe36e8ced1c6046759f9ce1d2655c8d731