Add draft refactor for _d_arrayctor

This aims to solve the warnings issued by the compiler when lowering
to strongly pure calls such as `_d_arrayctor(a, b)` and ignoring the
return value.

Signed-off-by: Teodor Dutu <teodor.dutu@gmail.com>

Author: teodutu

src/core/internal/array/construction.d

@@ -9,6 +9,8 @@
 */
 module core.internal.array.construction;
 
+import core.internal.traits : Unqual;
+
 /**
  * Does array initialization (not assignment) from another array of the same element type.
  * Params:
@@ -21,7 +23,8 @@ module core.internal.array.construction;
  *  purity, and throwabilty checks. To prevent breaking existing code, this function template
  *  is temporarily declared `@trusted` until the implementation can be brought up to modern D expectations.
  */
-Tarr _d_arrayctor(Tarr : T[], T)(return scope Tarr to, scope Tarr from) @trusted
+Tarr1 _d_arrayctor(Tarr1 : T1[], Tarr2 : T2[], T1, T2)(scope Tarr2 from, size_t length) @trusted
+    if (is(Unqual!T1 == Unqual!T2))
 {
     pragma(inline, false);
     import core.internal.traits : hasElaborateCopyConstructor, Unqual;
@@ -30,7 +33,15 @@ Tarr _d_arrayctor(Tarr : T[], T)(return scope Tarr to, scope Tarr from) @trusted
     import core.stdc.stdint : uintptr_t;
     debug(PRINTF) import core.stdc.stdio : printf;
 
-    debug(PRINTF) printf("_d_arrayctor(to = %p,%d, from = %p,%d) size = %d\n", from.ptr, from.length, to.ptr, to.length, T.tsize);
+    debug(PRINTF) printf("_d_arrayctor(to = %p,%d, from = %p,%d) size = %d\n", from.ptr, from.length, to.ptr, to.length, T1.tsize);
+
+    Tarr1 to;
+    // Check if Tarr1 is a dynamic array.
+    // Otherwise, to.length is already set.
+    static if (__traits(compiles, {to.length = length;}))
+    {
+        to.length = length;
+    }
 
     void[] vFrom = (cast(void*)from.ptr)[0..from.length];
     void[] vTo = (cast(void*)to.ptr)[0..to.length];
@@ -46,13 +57,11 @@ Tarr _d_arrayctor(Tarr : T[], T)(return scope Tarr to, scope Tarr from) @trusted
         (cast(Type)&enforceRawArraysConformableNogc)(action, elementSize, a1, a2, false);
     }
 
-    enforceRawArraysConformable("initialization", T.sizeof, vFrom, vTo);
+    enforceRawArraysConformable("initialization", T1.sizeof, vFrom, vTo);
 
-    static if (hasElaborateCopyConstructor!T)
+    static if (hasElaborateCopyConstructor!T1)
     {
-        // Use uint instead of size_t as a temporary workaround until this bug is fixed:
-        // https://issues.dlang.org/show_bug.cgi?id=22372
-        uint i;
+        size_t i;
         try
         {
             for (i = 0; i < to.length; i++)
@@ -64,7 +73,7 @@ Tarr _d_arrayctor(Tarr : T[], T)(return scope Tarr to, scope Tarr from) @trusted
             */
             while (i--)
             {
-                auto elem = cast(Unqual!T*)&to[i];
+                auto elem = cast(Unqual!T1*)&to[i];
                 destroy(*elem);
             }
 
@@ -74,7 +83,7 @@ Tarr _d_arrayctor(Tarr : T[], T)(return scope Tarr to, scope Tarr from) @trusted
     else
     {
         // blit all elements at once
-        memcpy(cast(void*) to.ptr, from.ptr, to.length * T.sizeof);
+        memcpy(cast(void*) to.ptr, from.ptr, to.length * T1.sizeof);
     }
 
     return to;
@@ -92,7 +101,7 @@ Tarr _d_arrayctor(Tarr : T[], T)(return scope Tarr to, scope Tarr from) @trusted
 
     S[4] arr1;
     S[4] arr2 = [S(0), S(1), S(2), S(3)];
-    _d_arrayctor(arr1[], arr2[]);
+    arr1 = _d_arrayctor!(S[4])(arr2[], arr1.length);
 
     assert(counter == 4);
     assert(arr1 == arr2);
@@ -115,7 +124,7 @@ Tarr _d_arrayctor(Tarr : T[], T)(return scope Tarr to, scope Tarr from) @trusted
 
     S[4] arr1;
     S[4] arr2 = [S(0), S(1), S(2), S(3)];
-    _d_arrayctor(arr1[], arr2[]);
+    arr1 = _d_arrayctor!(S[4])(arr2[], arr1.length);
 
     assert(counter == 4);
     assert(arr1 == arr2);
@@ -141,7 +150,7 @@ Tarr _d_arrayctor(Tarr : T[], T)(return scope Tarr to, scope Tarr from) @trusted
     {
         Throw[4] a;
         Throw[4] b = [Throw(1), Throw(2), Throw(3), Throw(4)];
-        _d_arrayctor(a[], b[]);
+        a = _d_arrayctor!(Throw[4])(b[], a.length);
     }
     catch (Exception)
     {
@@ -166,7 +175,7 @@ Tarr _d_arrayctor(Tarr : T[], T)(return scope Tarr to, scope Tarr from) @trusted
     {
         NoThrow[4] a;
         NoThrow[4] b = [NoThrow(1), NoThrow(2), NoThrow(3), NoThrow(4)];
-        _d_arrayctor(a[], b[]);
+        a = _d_arrayctor!(NoThrow[4])(b[], a.length);
     }
     catch (Exception)
     {
@@ -190,7 +199,6 @@ Tarr _d_arrayctor(Tarr : T[], T)(return scope Tarr to, scope Tarr from) @trusted
 void _d_arraysetctor(Tarr : T[], T)(scope Tarr p, scope ref T value) @trusted
 {
     pragma(inline, false);
-    import core.internal.traits : Unqual;
     import core.lifetime : copyEmplace;
 
     size_t i;
@@ -273,7 +281,7 @@ void _d_arraysetctor(Tarr : T[], T)(scope Tarr p, scope ref T value) @trusted
     {
         Throw[4] a;
         Throw[4] b = [Throw(1), Throw(2), Throw(3), Throw(4)];
-        _d_arrayctor(a[], b[]);
+        a = _d_arrayctor!(Throw[4])(b[], a.length);
     }
     catch (Exception)
     {