chore(*): Minor tweaks. Console warn on invalid setup.

Author: MKirova

projects/igniteui-angular/src/lib/data-operations/merge-strategy.ts

@@ -14,6 +14,7 @@ export interface IGridMergeStrategy {
         activeRowIndex? : number,
         grid?: GridType
     ) => any[];
+    comparer: (prevRecord: any, record: any, field: string) => boolean;
 }
 
 export class DefaultMergeStrategy implements IGridMergeStrategy {

projects/igniteui-angular/src/lib/grids/columns/column.component.ts

@@ -115,7 +115,17 @@ export class IgxColumnComponent implements AfterContentInit, OnDestroy, ColumnTy
      *
      */
     @Input()
-    public merge = false;
+    public get merge() {
+        return this._merge;
+    }
+
+    public set merge(value) {
+        if (this.grid.hasColumnLayouts) {
+            console.warn('Merging is not supported with multi-row layouts.');
+            return;
+        }
+        this._merge = value;
+    }
 
     /**
      * @hidden @internal
@@ -1911,6 +1921,10 @@ export class IgxColumnComponent implements AfterContentInit, OnDestroy, ColumnTy
      * @hidden
      */
     protected _groupable = false;
+    /**
+     * @hidden
+     */
+    protected _merge = false;
     /**
      *  @hidden
      */