Struct literal/constructor call should make rvalue. Related issue is issue5178. Test code: ---- struct S // has default parameterized constructor { int n; } struct T // has normal constructor { this(int n){} // ref T __ctor(int n){ return this; } // dmd generates internally like this } struct T2 { template __ctor() // workaround { T2 __ctor(int n){ return this; } // return copied rvalue } } // lvalue checker bool checker(T...)(auto ref T t){ return __traits(isRef, t[0]); } import std.stdio; void main() { int n = 20; S s = S(20); T t = T(20); T2 t2 = T2(20); writefln("%s / %s", checker( 10) , checker( n)); // false/true, ok writefln("%s / %s", checker( S(10)), checker( s)); // true /true, NG (Fixed by issue5178 patch) writefln("%s / %s", checker( T(10)), checker( t)); // true /true, NG!!! writefln("%s / %s", checker(T2(10)), checker(t2)); // false/true, ok } ----
Fixing thi bug is difficult for me. DMD internally behavior is... 1.Elaborate constructor returns this reference internally. -> see CtorDeclaration::semantic() 2.Elaborate constructor call T(args) is translated like (T __ctmp, __ctmp.__ctor(args)) and __ctmp.__ctor returns ref T. -> see CallExp::semantic Trivial fix patch is follwing, but this causes copying value. ---- src/func.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/src/func.c b/src/func.c index c3fd455..ea48670 100644 --- a/src/func.c +++ b/src/func.c @@ -2953,7 +2953,7 @@ void CtorDeclaration::semantic(Scope *sc) #if STRUCTTHISREF if (ad && ad->isStructDeclaration()) - { ((TypeFunction *)type)->isref = 1; + { //((TypeFunction *)type)->isref = 1; if (!originalType) // Leave off the "ref" originalType = new TypeFunction(arguments, tret, varargs, LINKd, storage_class | sc->stc); ----
On 2.059, PS E:\DigitalMars\dmd2\samples> rdmd bug.d false / true false / true false / true false / true
*** This issue has been marked as a duplicate of issue 5889 ***