fix: append start/end info to more tags (#11930)

* fix: append start/end info to more tags

We should add them everywhere we can
Related https://github.com/sveltejs/language-tools/pull/2385

* changeset

---------

Co-authored-by: Rich Harris <rich.harris@vercel.com>

.changeset/orange-comics-prove.md

@@ -0,0 +1,5 @@
+---
+"svelte": patch
+---
+
+fix: append start/end info to `AssignmentPattern` and `VariableDeclarator`

packages/svelte/src/compiler/phases/1-parse/state/tag.js

@@ -281,10 +281,13 @@ function open(parser) {
 			parser.allow_whitespace();
 			if (parser.eat('=')) {
 				parser.allow_whitespace();
+				const right = read_expression(parser);
 				pattern = {
 					type: 'AssignmentPattern',
 					left: pattern,
-					right: read_expression(parser)
+					right: right,
+					start: pattern.start,
+					end: right.end
 				};
 			}
 
@@ -572,7 +575,7 @@ function special(parser) {
 			declaration: {
 				type: 'VariableDeclaration',
 				kind: 'const',
-				declarations: [{ type: 'VariableDeclarator', id, init }],
+				declarations: [{ type: 'VariableDeclarator', id, init, start: id.start, end: init.end }],
 				start: start + 2, // start at const, not at @const
 				end: parser.index - 1
 			}