Fix Issue 22105 - std.container.array.Array.length setter creates values of init-less types

std/algorithm/mutation.d

@@ -866,6 +866,9 @@ if (isInputRange!InputRange
 Initializes all elements of `range` with their `.init` value.
 Assumes that the elements of the range are uninitialized.
 
+This function is unavailable if `T` is a `struct` and  `T.this()` is annotated
+with `@disable`.
+
 Params:
         range = An
                 $(REF_ALTTEXT input range, isInputRange, std,range,primitives)
@@ -877,7 +880,8 @@ See_Also:
         $(LREF uninitializedFill)
  */
 void initializeAll(Range)(Range range)
-if (isInputRange!Range && hasLvalueElements!Range && hasAssignableElements!Range)
+if (isInputRange!Range && hasLvalueElements!Range && hasAssignableElements!Range
+    && __traits(compiles, { static ElementType!Range _; }))
 {
     import core.stdc.string : memset, memcpy;
     import std.traits : hasElaborateAssign, isDynamicArray;
@@ -1037,6 +1041,18 @@ if (is(Range == char[]) || is(Range == wchar[]))
     assert(xs[1].x == 3);
 }
 
+// https://issues.dlang.org/show_bug.cgi?id=22105
+@system unittest
+{
+    struct NoDefaultCtor
+    {
+        @disable this();
+    }
+
+    NoDefaultCtor[1] array = void;
+    static assert(!__traits(compiles, array[].initializeAll));
+}
+
 // move
 /**
 Moves `source` into `target`, via a destructive copy when necessary.

std/container/array.d

@@ -428,8 +428,6 @@ if (!is(immutable T == immutable bool))
 
         @property void length(size_t newLength)
         {
-            import std.algorithm.mutation : initializeAll;
-
             if (length >= newLength)
             {
                 // shorten
@@ -440,10 +438,22 @@ if (!is(immutable T == immutable bool))
                 _payload = _payload.ptr[0 .. newLength];
                 return;
             }
-            immutable startEmplace = length;
+
-            reserve(newLength);
+            static if (__traits(compiles, { static T _; }))
-            initializeAll(_payload.ptr[startEmplace .. newLength]);
+            {
-            _payload = _payload.ptr[0 .. newLength];
+                import std.algorithm.mutation : initializeAll;
+
+                immutable startEmplace = length;
+                reserve(newLength);
+                initializeAll(_payload.ptr[startEmplace .. newLength]);
+                _payload = _payload.ptr[0 .. newLength];
+            }
+            else
+            {
+                assert(0, "Cannot add elements to array because `" ~
+                    fullyQualifiedName!T ~ ".this()` is annotated with " ~
+                    "`@disable`.");
+            }
         }
 
         @property size_t capacity() const
@@ -901,12 +911,16 @@ if (!is(immutable T == immutable bool))
     /**
      * Sets the number of elements in the array to `newLength`. If `newLength`
      * is greater than `length`, the new elements are added to the end of the
-     * array and initialized with `T.init`.
+     * array and initialized with `T.init`. If `T` is a `struct` whose default
+     * constructor is annotated with `@disable`, `newLength` must be lower than
+     * or equal to `length`.
      *
      * Complexity:
      * Guaranteed $(BIGOH abs(length - newLength)) if `capacity >= newLength`.
      * If `capacity < newLength` the worst case is $(BIGOH newLength).
      *
+     * Precondition: `__traits(compiles, { static T _; }) || newLength <= length`
+     *
      * Postcondition: `length == newLength`
      */
     @property void length(size_t newLength)
@@ -1708,6 +1722,23 @@ if (!is(immutable T == immutable bool))
     assert(equal(a[], [1,2,3,4,5,6,7,8]));
 }
 
+// https://issues.dlang.org/show_bug.cgi?id=22105
+@system unittest
+{
+    import core.exception : AssertError;
+    import std.exception : assertThrown, assertNotThrown;
+
+    struct NoDefaultCtor
+    {
+        int i;
+        @disable this();
+        this(int j) { i = j; }
+    }
+
+    auto array = Array!NoDefaultCtor([NoDefaultCtor(1), NoDefaultCtor(2)]);
+    assertNotThrown!AssertError(array.length = 1);
+    assertThrown!AssertError(array.length = 5);
+}
 
 ////////////////////////////////////////////////////////////////////////////////
 // Array!bool