include checking for {@html} tags in invalid location

src/compiler/parse/errors.ts

@@ -111,6 +111,10 @@ export default {
 		code: 'invalid-logic-block-placement',
 		message: `{#${name}} logic block cannot be ${location}`
 	}),
+	invalid_tag_placement: (location: string, name: string) => ({
+		code: 'invalid-tag-placement',
+		message: `{@${name}} tag cannot be ${location}`
+	}),
 	invalid_ref_directive: (name: string) => ({
 		code: 'invalid-ref-directive',
 		message: `The ref directive is no longer supported — use \`bind:this={${name}}\` instead`

src/compiler/parse/state/tag.ts

@@ -527,6 +527,11 @@ function read_sequence(parser: Parser, done: () => boolean, location: string): T
 				parser.eat('#');
 				const name = parser.read_until(/[^a-z]/);
 				parser.error(parser_errors.invalid_logic_block_placement(location, name), index);
+			} else if (parser.match('@')) {
+				const index = parser.index - 1;
+				parser.eat('@');
+				const name = parser.read_until(/[^a-z]/);
+				parser.error(parser_errors.invalid_tag_placement(location, name), index);
 			}
 
 			flush(parser.index - 1);

test/validator/samples/html-block-in-attribute/errors.json

@@ -0,0 +1,9 @@
+[
+	{
+		"code": "invalid-tag-placement",
+		"message": "{@html} tag cannot be in attribute value",
+		"start": { "line": 1, "column": 12, "character": 12 },
+		"end": { "line": 1, "column": 12, "character": 12 },
+		"pos": 12
+	}
+]

test/validator/samples/html-block-in-attribute/input.svelte

@@ -0,0 +1 @@
+<div style="{@html text}" />

test/validator/samples/html-block-in-textarea/errors.json

@@ -0,0 +1,9 @@
+[
+	{
+		"code": "invalid-tag-placement",
+		"message": "{@html} tag cannot be inside <textarea>",
+		"start": { "line": 2, "column": 1, "character": 12 },
+		"end": { "line": 2, "column": 1, "character": 12 },
+		"pos": 12
+	}
+]

test/validator/samples/html-block-in-textarea/input.svelte

@@ -0,0 +1,3 @@
+<textarea>
+	{@html fruit}
+</textarea>