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Compiler Error C3551

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if a trailing return type is used then the leading return type shall be the single type-specifier 'auto' (not 'type')

The leading return type in trailing return type syntax must contain only auto.

// C3551.cpp
// compile with: /c
const auto func1() -> const int;   // C3551
auto* func2() -> int*;   // C3551
auto& func3() -> int&;   // C3551
auto&& func4() -> int&&;   // C3551
decltype(auto) func5() -> int;   // C3551

auto func6() -> int;   // OK