fix: don't show state_referenced_locally warning on types (#13177)

Add a new visitor to the "strip TS AST" logic. Strictly speaking this results in incorrect ASTs but esrap, our printer, just ignores them at those positions, so we can do that.
An alternative would be to adjust zimmerframe to be able to return something to say "delete this node"
Fixes #13173

Author: paoloricciuti

.changeset/five-suns-roll.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: don't show `state_referenced_locally` warning on types

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

@@ -73,6 +73,11 @@ const visitors = {
 	TSNonNullExpression(node, context) {
 		return context.visit(node.expression);
 	},
+	TSTypeAnnotation() {
+		// This isn't correct, strictly speaking, and could result in invalid ASTs (like an empty statement within function parameters),
+		// but esrap, our printing tool, just ignores these AST nodes at invalid positions, so it's fine
+		return b.empty;
+	},
 	TSInterfaceDeclaration() {
 		return b.empty;
 	},
@@ -94,15 +99,6 @@ const visitors = {
 		}
 		return node.parameter;
 	},
-	Identifier(node) {
-		if (node.typeAnnotation) {
-			return {
-				...node,
-				typeAnnotation: null
-			};
-		}
-		return node;
-	},
 	FunctionExpression: remove_this_param,
 	FunctionDeclaration: remove_this_param,
 	TSDeclareFunction() {

packages/svelte/tests/validator/samples/state-referenced-locally-types/input.svelte

@@ -0,0 +1,6 @@
+<script lang="ts">
+	let { a }: { a: string } = $state({});
+	let { b }: { b: string } = $derived(a);
+</script>
+
+<button onclick={()=>a++}></button>

packages/svelte/tests/validator/samples/state-referenced-locally-types/warnings.json

@@ -0,0 +1 @@
+[]