a this given as text warns again, at the attribute as before

packages/svelte/src/compiler/phases/1-parse/index.js

@@ -299,8 +299,15 @@ class Finish {
 						: /** @type {any} */ ({});
 				if (node.type === 'SvelteElement') {
 					// a tag named in text is the literal Svelte writes by hand, quoted its way
-					if (node.tag.type === 'Literal' && node.tag.raw === node.tag.value)
+					if (node.tag.type === 'Literal' && node.tag.raw === node.tag.value) {
+						const { start, end } = /** @type {{ start: number; end: number }} */ (node.tag);
+						const quoted = this.template[start - 1] === '"' || this.template[start - 1] === "'";
+						w.svelte_element_invalid_this({
+							start: this.template.lastIndexOf('this', start),
+							end: quoted ? end + 1 : end
+						});
 						node.tag.raw = `'${node.tag.value}'`;
+					}
 					node.metadata.expression = new ExpressionMetadata();
 				}
 				if (node.type === 'SvelteComponent' || node.type === 'Component') {

packages/svelte/tests/validator/samples/svelte-element-invalid-this/input.svelte

@@ -0,0 +1,2 @@
+<svelte:element this="div" />
+<svelte:element this=span>text</svelte:element>

packages/svelte/tests/validator/samples/svelte-element-invalid-this/warnings.json

@@ -0,0 +1,26 @@
+[
+	{
+		"code": "svelte_element_invalid_this",
+		"message": "`this` should be an `{expression}`. Using a string attribute value will cause an error in future versions of Svelte",
+		"start": {
+			"column": 16,
+			"line": 1
+		},
+		"end": {
+			"column": 26,
+			"line": 1
+		}
+	},
+	{
+		"code": "svelte_element_invalid_this",
+		"message": "`this` should be an `{expression}`. Using a string attribute value will cause an error in future versions of Svelte",
+		"start": {
+			"column": 16,
+			"line": 2
+		},
+		"end": {
+			"column": 25,
+			"line": 2
+		}
+	}
+]