Merge pull request #1762 from alixander/array-class

d2ir: fix merging boards with array composites

Author: alixander

ci/release/changelogs/next.md

@@ -3,3 +3,5 @@
 #### Improvements 🧹
 
 #### Bugfixes ⛑️
+
+- Fix importing files that override an existing value with an array. [#1762](https://github.com/terrastruct/d2/pull/1762)

d2ir/import_test.go

@@ -199,6 +199,18 @@ label: meow`,
 				assert.Success(t, err)
 			},
 		},
+		{
+			name: "merge-arrays",
+			run: func(t testing.TB) {
+				_, err := compileFS(t, "index.d2", map[string]string{
+					"index.d2": `x.class: [a]
+...@d
+`,
+					"d.d2": `x.class: [b]`,
+				})
+				assert.Success(t, err)
+			},
+		},
 	}
 
 	runa(t, tca)

d2ir/merge.go

@@ -30,7 +30,7 @@ func OverlayField(bf, of *Field) {
 		if bf.Map() != nil && of.Map() != nil {
 			OverlayMap(bf.Map(), of.Map())
 		} else {
-			bf.Composite = of.Composite.Copy(bf).(*Map)
+			bf.Composite = of.Composite.Copy(bf).(Composite)
 		}
 	}