Fix Issue 18806 - InputRange for std.algorithm.minIndex

std/algorithm/searching.d

@@ -3789,7 +3789,7 @@ irreflexive (`pred(a, a)` is `false`).
 Params:
     pred = The ordering predicate to use to determine the extremum (minimum or
         maximum) element.
-    range = The $(REF_ALTTEXT input range, isInputRange, std,range,primitives) to search.
+    range = The $(REF_ALTTEXT forward range, isForwardRange, std,range,primitives) to search.
 
 Returns: The position of the minimum (respectively maximum) element of forward
 range `range`, i.e. a subrange of `range` starting at the position of  its
@@ -3909,7 +3909,7 @@ See_Also:
     $(LREF maxIndex), $(REF min, std,algorithm,comparison), $(LREF minCount), $(LREF minElement), $(LREF minPos)
  */
 sizediff_t minIndex(alias pred = "a < b", Range)(Range range)
-if (isForwardRange!Range && !isInfinite!Range &&
+if (isInputRange!Range && !isInfinite!Range &&
     is(typeof(binaryFun!pred(range.front, range.front))))
 {
     if (range.empty) return -1;
@@ -4009,6 +4009,40 @@ if (isForwardRange!Range && !isInfinite!Range &&
     assert(arr2d.minIndex!"a[1] < b[1]" == 2);
 }
 
+@safe nothrow pure unittest
+{
+    // InputRange test
+
+    static struct InRange
+    {
+        @property int front()
+        {
+            return arr[index];
+        }
+
+        bool empty() const
+        {
+            return arr.length == index;
+        }
+
+        void popFront()
+        {
+            index++;
+        }
+
+        int[] arr;
+        size_t index = 0;
+    }
+
+    static assert(isInputRange!InRange);
+
+    auto arr1 = InRange([5, 2, 3, 4, 5, 3, 6]);
+    auto arr2 = InRange([7, 3, 8, 2, 1, 4]);
+
+    assert(arr1.minIndex == 1);
+    assert(arr2.minIndex == 4);
+}
+
 /**
 Computes the index of the first occurrence of `range`'s maximum element.