add actionable advice

Author: dummdidumm

packages/svelte/src/compiler/migrate/index.js

@@ -246,7 +246,7 @@ export function migrate(source, { filename, use_ts } = {}) {
 			const has_rune_binding = !!state.scope.get(rune);
 			if (has_rune_binding) {
 				throw new MigrationError(
-					`migrating this component would require adding a \`$${rune}\` but there's already a variable named ${rune}`
+					`migrating this component would require adding a \`$${rune}\` rune but there's already a variable named ${rune}.\n     Rename the variable and try again or migrate by hand.`
 				);
 			}
 		}
@@ -670,14 +670,13 @@ const instance_script = {
 			}
 
 			/**
-			 *
 			 * @param {"state"|"derived"} rune
 			 */
 			function check_rune_binding(rune) {
 				const has_rune_binding = !!state.scope.get(rune);
 				if (has_rune_binding) {
 					throw new MigrationError(
-						`can't migrate \`${state.str.original.substring(/** @type {number} */ (node.start), node.end)}\` to \`$${rune}\` because there's a variable named ${rune}`
+						`can't migrate \`${state.str.original.substring(/** @type {number} */ (node.start), node.end)}\` to \`$${rune}\` because there's a variable named ${rune}.\n     Rename the variable and try again or migrate by hand.`
 					);
 				}
 			}
@@ -901,7 +900,7 @@ const instance_script = {
 			const has_rune_binding = state.scope.get(rune);
 			if (has_rune_binding) {
 				throw new MigrationError(
-					`can't migrate \`$: ${state.str.original.substring(/** @type {number} */ (node.body.start), node.body.end)}\` to \`$${rune}\` because there's a variable named ${rune}`
+					`can't migrate \`$: ${state.str.original.substring(/** @type {number} */ (node.body.start), node.body.end)}\` to \`$${rune}\` because there's a variable named ${rune}.\n     Rename the variable and try again or migrate by hand.`
 				);
 			}
 		}

packages/svelte/tests/migrate/samples/impossible-migrate-$bindable-bindable-var-1/output.svelte

@@ -1,4 +1,5 @@
-<!-- @migration-task Error while migrating Svelte code: migrating this component would require adding a `$bindable` but there's already a variable named bindable -->
+<!-- @migration-task Error while migrating Svelte code: migrating this component would require adding a `$bindable` rune but there's already a variable named bindable.
+     Rename the variable and try again or migrate by hand. -->
 <script>
 	let bindable;
 	export let something;

packages/svelte/tests/migrate/samples/impossible-migrate-$derived-derived-var-1/output.svelte

@@ -1,4 +1,5 @@
-<!-- @migration-task Error while migrating Svelte code: can't migrate `$: other = name;` to `$derived` because there's a variable named derived -->
+<!-- @migration-task Error while migrating Svelte code: can't migrate `$: other = name;` to `$derived` because there's a variable named derived.
+     Rename the variable and try again or migrate by hand. -->
 <script>
 	let name = 'world';
 

packages/svelte/tests/migrate/samples/impossible-migrate-$derived-derived-var-2/output.svelte

@@ -1,4 +1,5 @@
-<!-- @migration-task Error while migrating Svelte code: migrating this component would require adding a `$derived` but there's already a variable named derived -->
+<!-- @migration-task Error while migrating Svelte code: migrating this component would require adding a `$derived` rune but there's already a variable named derived.
+     Rename the variable and try again or migrate by hand. -->
 <script>
 	let derived;
 </script>

packages/svelte/tests/migrate/samples/impossible-migrate-$derived-derived-var-4/output.svelte

@@ -1,4 +1,5 @@
-<!-- @migration-task Error while migrating Svelte code: can't migrate `let other;` to `$derived` because there's a variable named derived -->
+<!-- @migration-task Error while migrating Svelte code: can't migrate `let other;` to `$derived` because there's a variable named derived.
+     Rename the variable and try again or migrate by hand. -->
 <script>
 	let name = 'world';
 

packages/svelte/tests/migrate/samples/impossible-migrate-$props-props-var-1/output.svelte

@@ -1,4 +1,5 @@
-<!-- @migration-task Error while migrating Svelte code: migrating this component would require adding a `$props` but there's already a variable named props -->
+<!-- @migration-task Error while migrating Svelte code: migrating this component would require adding a `$props` rune but there's already a variable named props.
+     Rename the variable and try again or migrate by hand. -->
 <script>
 	let props;
 	export let something;

packages/svelte/tests/migrate/samples/impossible-migrate-$state-state-var-1/output.svelte

@@ -1,4 +1,5 @@
-<!-- @migration-task Error while migrating Svelte code: can't migrate `let other;` to `$state` because there's a variable named state -->
+<!-- @migration-task Error while migrating Svelte code: can't migrate `let other;` to `$state` because there's a variable named state.
+     Rename the variable and try again or migrate by hand. -->
 <script>
 	let state = 'world';
 

packages/svelte/tests/migrate/samples/impossible-migrate-$state-state-var-2/output.svelte

@@ -1,4 +1,5 @@
-<!-- @migration-task Error while migrating Svelte code: can't migrate `let other = 42;` to `$state` because there's a variable named state -->
+<!-- @migration-task Error while migrating Svelte code: can't migrate `let other = 42;` to `$state` because there's a variable named state.
+     Rename the variable and try again or migrate by hand. -->
 <script>
 	let state = 'world';
 

packages/svelte/tests/migrate/samples/impossible-migrate-$state-state-var-3/output.svelte

@@ -1,4 +1,5 @@
-<!-- @migration-task Error while migrating Svelte code: can't migrate `$: other = 42;` to `$state` because there's a variable named state -->
+<!-- @migration-task Error while migrating Svelte code: can't migrate `$: other = 42;` to `$state` because there's a variable named state.
+     Rename the variable and try again or migrate by hand. -->
 <script>
 	let state = 'world';