Bug 23751 – Returning by ref from opApply fools DIP1000

DMD 2.102.1: Test case 1: --- struct S{ int x; int opApply(scope int delegate(ref int x)@safe @nogc dg)@safe @nogc{ return dg(x); } } ref int foo(ref S s)@safe @nogc{ foreach(ref x;s) return x; assert(0); } int *escapeStack()@safe{ S s; return &foo(s); } void main()@safe{ import std.stdio; auto p=escapeStack(); writeln(*p); // 0 writeln("overwrite stack"); writeln(*p); // garbage } --- Test case 2: --- struct S{ int x; int opApply(scope int delegate(ref int x)@safe @nogc dg)@safe @nogc{ return dg(x); } } ref int foo(ref S s)@safe @nogc{ foreach(x;s) return x; assert(0); } int *escapeStack()@safe{ S s; return &foo(s); } void overwriteStack(int depth)@safe{ auto s=S(2); import std.stdio; if(depth==0) writeln("overwrite stack: ",s); else overwriteStack(depth-1); } void main()@safe{ import std.stdio; auto p=escapeStack(); writeln(*p); // 0 overwriteStack(10); writeln(*p); // garbage } --- (Partial reboot of Issue 23739 with proper test cases.)

Nice try, Timon. ;)

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