column: assert nested before delegating so the error names column()

column(null, $indexKey) delegated to indexBy() before asserting, so a flat array threw "indexBy(): Expected a nested array" - a method name the caller never wrote and can't grep for. Same convention as pluckNth(): assert first, then delegate.

Author: daveedis

src/SmartArrayBase.php

@@ -820,11 +820,13 @@ public function columnAt(int $index): static
      */
     public function column(int|string|null $columnKey, int|string|null $indexKey = null): static
     {
+        $this->assertNestedArray(); // assert here so the error names column(), not indexBy()
+
         if ($columnKey === null && $indexKey !== null) {
             return $this->indexBy((string)$indexKey);
         }
 
-        $this->assertNestedArray();
+
         if ($columnKey !== null) {
             $this->warnIfMissing($columnKey);
         }

tests/Unit/ProjectionTest.php

@@ -150,6 +150,17 @@ public function testColumnWithBothArgumentsNullReturnsRenumberedRows(string $cla
         $this->assertSame([['id' => 1], ['id' => 2]], $result->toArray());
     }
 
+    #[DataProvider('modeProvider')]
+    public function testColumnOnFlatThrowsNamingColumn(string $class): void
+    {
+        // Covers the indexBy() delegation shape: the error names the method the
+        // caller actually wrote, not the internal delegate
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('column(): Expected a nested array, but got a flat array');
+
+        $class::new(['a', 'b'])->column(null, 'x');
+    }
+
     //endregion
     //region indexBy()