Bug 4891 – Assignment from non-pure function to pure function pointer compiles when it shouldn't

Take this program struct S { public: this(int function(int) pure func) { _func = func; } @property int function(int) pure func() { return func; } private: int function(int) pure _func; } int add1(int num) { return num + 1; } void main() { auto s = S(&add1); } The construction of s should not compile because add1() is not a pure function. Granted, it could be pure if I declared it as such, but I didn't. And the compiler isn't figuring out that add1() could be pure and letting it through because of that because if I add a writeln() call to add1(), it still compiles.

Oh, there's an error in my example - func return func instead of _func, resulting infinite recursion and therefore a segfault. I could have removed that function for the bug report anyway.

See bug 3833

This is a dupe of 3797, the purity of a function pointer (among other things) is not checked when performing implicit conversions. With dmd pull 88 you get the following error from dmd: testx.d(26): Error: constructor testx.S.this (int function(int) pure func) is no t callable using argument types (int function(int num)) testx.d(26): Error: cannot implicitly convert expression (& add1) of type int fu nction(int num) to int function(int) pure *** This issue has been marked as a duplicate of issue 3797 ***