Bug 17718 – [scope] function literal arguments can be escaped

cat > bug.d << CODE @safe: struct S { int* p; int* leak() return scope { return p; } } alias f = function int*(scope S s) { return s.leak; }; // broken int* f(scope S s) { return s.leak; } // works CODE dmd -c -dip1000 bug

If I change the structure to: struct S { int p; int* leak() return scope { return &p; } } I get: scope_bug17718.d(9): Error: returning s.leak() escapes a reference to parameter s, perhaps annotate with return Where exactly is one supposed to add return?

(Where line 9 is the `alias f = ...` same as in the original example.)

What's happening here is that the function literal f is getting its attributes inferred, so 'return scope' is inferred. The explicit function f is not getting its attributes inferred, the parameter is 'scope', not 'return scope', and so it errors. If the latter is changed to: auto f(scope S s) { return s.leak; } then no error occurs, because attribute inference is done for auto functions. The compiler is working correctly.