Implement dynamic slot attribute

src/compiler/compile/nodes/Element.ts

@@ -529,10 +529,6 @@ export default class Element extends Node {
 			}
 
 			if (name === 'slot') {
-				if (!attribute.is_static) {
-					return component.error(attribute, compiler_errors.invalid_slot_attribute);
-				}
-
 				if (component.slot_outlets.has(name)) {
 					return component.error(attribute, compiler_errors.duplicate_slot_attribute(name));
 

src/compiler/compile/nodes/SlotTemplate.ts

@@ -16,6 +16,7 @@ export default class SlotTemplate extends Node {
 	const_tags: ConstTag[];
 	slot_attribute: Attribute;
 	slot_template_name: string = 'default';
+	is_static: boolean = true;
 
 	constructor(
 		component: Component,
@@ -44,14 +45,17 @@ export default class SlotTemplate extends Node {
 				case 'Attribute': {
 					if (node.name === 'slot') {
 						this.slot_attribute = new Attribute(component, this, scope, node);
-						if (!this.slot_attribute.is_static) {
-							return component.error(node, compiler_errors.invalid_slot_attribute);
+						if (this.slot_attribute.is_static) {
+							const value = this.slot_attribute.get_static_value();
+							if (typeof value === 'boolean') {
+								return component.error(node, compiler_errors.invalid_slot_attribute_value_missing);
+							}
+							this.slot_template_name = value as string;
+							this.is_static = true;
+						} else {
+							this.slot_template_name = component.get_unique_name('dynamic_slot_template').name;
+							this.is_static = false;
 						}
-						const value = this.slot_attribute.get_static_value();
-						if (typeof value === 'boolean') {
-							return component.error(node, compiler_errors.invalid_slot_attribute_value_missing);
-						}
-						this.slot_template_name = value as string;
 						break;
 					}
 					throw new Error(`Invalid attribute '${node.name}' in <svelte:fragment>`);

src/compiler/compile/render_dom/wrappers/InlineComponent/index.ts

@@ -29,7 +29,8 @@ const regex_invalid_variable_identifier_characters = /[^a-zA-Z_$]/g;
 
 export default class InlineComponentWrapper extends Wrapper {
 	var: Identifier;
-	slots: Map<string, SlotDefinition> = new Map();
+	slots: Map<SlotTemplate, SlotDefinition> = new Map();
+	staic_slot_names: Set<string> = new Set();
 	node: InlineComponent;
 	fragment: FragmentWrapper;
 	children: Array<Wrapper | FragmentWrapper> = [];
@@ -95,14 +96,20 @@ export default class InlineComponentWrapper extends Wrapper {
 		block.add_outro();
 	}
 
-	set_slot(name: string, slot_definition: SlotDefinition) {
-		if (this.slots.has(name)) {
-			if (name === 'default') {
-				throw new Error('Found elements without slot attribute when using slot="default"');
+	set_slot(slot: SlotTemplate, slot_definition: SlotDefinition) {
+		if (slot.is_static) {
+			const name = slot.slot_template_name;
+			if (this.staic_slot_names.has(name)) {
+				if (name === 'default') {
+					throw new Error('Found elements without slot attribute when using slot="default"');
+				}
+				throw new Error(`Duplicate slot name "${name}" in <${this.node.name}>`);
+			} else {
+				this.staic_slot_names.add(name);
 			}
-			throw new Error(`Duplicate slot name "${name}" in <${this.node.name}>`);
 		}
-		this.slots.set(name, slot_definition);
+
+		this.slots.set(slot, slot_definition);
 	}
 
 	warn_if_reactive() {
@@ -167,8 +174,10 @@ export default class InlineComponentWrapper extends Wrapper {
 		const initial_props = this.slots.size > 0
 			? [
 				p`$$slots: {
-					${Array.from(this.slots).map(([name, slot]) => {
-						return p`${name}: [${slot.block.name}, ${slot.get_context || null}, ${slot.get_changes || null}]`;
+					${Array.from(this.slots).map(([slot_template, slot]) => {
+						const { is_static, slot_template_name, slot_attribute } = slot_template;
+						const slot_expression = is_static ? { type: 'Literal', value: slot_template_name } : slot_attribute.get_value(block);
+						return p`[${slot_expression}]: [${slot.block.name}, ${slot.get_context || null}, ${slot.get_changes || null}]`;
 					})}
 				}`,
 				p`$$scope: {

src/compiler/compile/render_dom/wrappers/SlotTemplate.ts

@@ -52,10 +52,7 @@ export default class SlotTemplateWrapper extends Wrapper {
 			if (!seen.has(l.name.name)) lets.push(l);
 		});
 
-		this.parent.set_slot(
-			slot_template_name,
-			get_slot_definition(this.block, scope, lets)
-		);
+		this.parent.set_slot(this.node, get_slot_definition(this.block, scope, lets));
 
 		this.fragment = new FragmentWrapper(
 			renderer,

src/compiler/compile/render_ssr/handlers/InlineComponent.ts

@@ -77,9 +77,9 @@ export default function(node: InlineComponent, renderer: Renderer, options: Rend
 			slot_scopes
 		}));
 
-		slot_scopes.forEach(({ input, output, statements }, name) => {
+		slot_scopes.forEach(({ input, output, statements }, slot_exp) => {
 			slot_fns.push(
-				p`${name}: (${input}) => { ${statements}; return ${output}; }`
+				p`[${slot_exp}]: (${input}) => { ${statements}; return ${output}; }`
 			);
 		});
 	}

src/compiler/compile/render_ssr/handlers/Slot.ts

@@ -9,7 +9,7 @@ export default function(node: Slot, renderer: Renderer, options: RenderOptions &
 	slot_scopes: Map<any, any>;
 }) {
 	const slot_data = get_slot_data(node.values);
-	const slot = node.get_static_attribute_value('slot');
+	const slot = node.values.get('slot')?.get_value(null);
 	const nearest_inline_component = node.find_nearest(/InlineComponent/);
 
 	if (slot && nearest_inline_component) {

src/compiler/compile/render_ssr/handlers/SlotTemplate.ts

@@ -29,7 +29,8 @@ export default function(node: SlotTemplate, renderer: Renderer, options: RenderO
 			throw new Error(`Duplicate slot name "${node.slot_template_name}" in <${parent_inline_component.name}>`);
 		}
 
-		options.slot_scopes.set(node.slot_template_name, {
+		const slot_expression = node.is_static ? { type: 'Literal', value: node.slot_template_name } : node.slot_attribute.get_value(null);
+		options.slot_scopes.set(slot_expression, {
 			input: get_slot_scope(node.lets),
 			output: slot_fragment_content,
 			statements: get_const_tags(node.const_tags)