fix: allow for duplicate var declarations (#15382)

Author: paoloricciuti

.changeset/spotty-drinks-tan.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: allow for duplicate `var` declarations

packages/svelte/src/compiler/phases/scope.js

@@ -161,8 +161,12 @@ export class Scope {
 		}
 
 		if (this.declarations.has(node.name)) {
-			// This also errors on var/function types, but that's arguably a good thing
-			e.declaration_duplicate(node, node.name);
+			const binding = this.declarations.get(node.name);
+			if (binding && binding.declaration_kind !== 'var' && declaration_kind !== 'var') {
+				// This also errors on function types, but that's arguably a good thing
+				// declaring function twice is also caught by acorn in the parse phase
+				e.declaration_duplicate(node, node.name);
+			}
 		}
 
 		const binding = new Binding(this, node, kind, declaration_kind, initial);

packages/svelte/tests/validator/samples/multiple-var-same-name/errors.json

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

packages/svelte/tests/validator/samples/multiple-var-same-name/input.svelte

@@ -0,0 +1,6 @@
+<script>
+	var test = "";
+	var test = 42;
+</script>
+
+{test}