d2parser: Error on unquoted strings starting with ...@

d2ast/d2ast.go

@@ -257,6 +257,13 @@ func (p Position) Subtract(r rune, byUTF16 bool) Position {
 	return p
 }
 
+func (p Position) AdvanceString(s string, byUTF16 bool) Position {
+	for _, r := range s {
+		p = p.Advance(r, byUTF16)
+	}
+	return p
+}
+
 func (p Position) SubtractString(s string, byUTF16 bool) Position {
 	for _, r := range s {
 		p = p.Subtract(r, byUTF16)

d2parser/parse.go

@@ -1046,6 +1046,14 @@ func (p *parser) parseUnquotedString(inKey bool) (s *d2ast.UnquotedString) {
 		s.Value = append(s.Value, d2ast.InterpolationBox{String: &sv, StringRaw: &rawv})
 	}()
 
+	_s, eof := p.peekn(4)
+	p.rewind()
+	if !eof {
+		if _s == "...@" {
+			p.errorf(p.readerPos, p.pos.AdvanceString("...@", p.utf16), "unquoted strings cannot begin with ...@ as that's import spread syntax")
+		}
+	}
+
 	for {
 		r, eof := p.peek()
 		if eof {

d2parser/parse_test.go

@@ -463,6 +463,12 @@ func testImport(t *testing.T) {
 				assert.ErrorString(t, err, "d2/testdata/d2parser/TestParse/import/#07.d2:1:1: @file is not a valid import, did you mean ...@file?")
 			},
 		},
+		{
+			text: "meow: ...@file",
+			assert: func(t testing.TB, ast *d2ast.Map, err error) {
+				assert.ErrorString(t, err, "d2/testdata/d2parser/TestParse/import/#08.d2:1:10: unquoted strings cannot begin with ...@ as that's import spread syntax")
+			},
+		},
 	}
 
 	runa(t, tca)

testdata/d2parser/TestParse/import/#03.exp.json

@@ -24,7 +24,7 @@
           "primary": {},
           "value": {
             "array": {
-              "range": "d2/testdata/d2parser/TestParse/import/#03.d2,0:3:3-0:15:15",
+              "range": "d2/testdata/d2parser/TestParse/import/#03.d2,0:3:3-0:16:16",
               "nodes": [
                 {
                   "import": {

testdata/d2parser/TestParse/import/#08.exp.json

@@ -0,0 +1,48 @@
+{
+  "ast": {
+    "range": "d2/testdata/d2parser/TestParse/import/#08.d2,0:0:0-0:14:14",
+    "nodes": [
+      {
+        "map_key": {
+          "range": "d2/testdata/d2parser/TestParse/import/#08.d2,0:0:0-0:14:14",
+          "key": {
+            "range": "d2/testdata/d2parser/TestParse/import/#08.d2,0:0:0-0:4:4",
+            "path": [
+              {
+                "unquoted_string": {
+                  "range": "d2/testdata/d2parser/TestParse/import/#08.d2,0:0:0-0:4:4",
+                  "value": [
+                    {
+                      "string": "meow",
+                      "raw_string": "meow"
+                    }
+                  ]
+                }
+              }
+            ]
+          },
+          "primary": {},
+          "value": {
+            "unquoted_string": {
+              "range": "d2/testdata/d2parser/TestParse/import/#08.d2,0:6:6-0:14:14",
+              "value": [
+                {
+                  "string": "...@file",
+                  "raw_string": "...@file"
+                }
+              ]
+            }
+          }
+        }
+      }
+    ]
+  },
+  "err": {
+    "errs": [
+      {
+        "range": "d2/testdata/d2parser/TestParse/import/#08.d2,0:9:9-0:10:10",
+        "errmsg": "d2/testdata/d2parser/TestParse/import/#08.d2:1:10: unquoted strings cannot begin with ...@ as that's import spread syntax"
+      }
+    ]
+  }
+}