syntax/types: Derive VisitorKeysMap type from visitorKeys object …

…definition
glimmerjs · Dec 24, 2018 · ebe2ef1 · ebe2ef1
1 parent a018e58
commit ebe2ef1
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Showing 2 changed files with 30 additions and 45 deletions.
diff --git a/packages/@glimmer/syntax/lib/types/nodes.ts b/packages/@glimmer/syntax/lib/types/nodes.ts
@@ -1,3 +1,5 @@
+import { VisitorKeysMap } from './visitor-keys';
+
 export type Option<T> = T | null;
 
 export interface BaseNode {
@@ -206,29 +208,6 @@ export interface Nodes {
   HashPair: HashPair;
 }
 
-export interface VisitorKeysMap {
-  Program: ['body'];
-  MustacheStatement: ['path', 'params', 'hash'];
-  BlockStatement: ['path', 'params', 'hash', 'program', 'inverse'];
-  ElementModifierStatement: ['path', 'params', 'hash'];
-  PartialStatement: ['name', 'params', 'hash'];
-  CommentStatement: never[];
-  MustacheCommentStatement: never[];
-  ElementNode: ['attributes', 'modifiers', 'children', 'comments'];
-  AttrNode: ['value'];
-  TextNode: never[];
-  ConcatStatement: ['parts'];
-  SubExpression: ['path', 'params', 'hash'];
-  PathExpression: never[];
-  StringLiteral: never[];
-  BooleanLiteral: never[];
-  NumberLiteral: never[];
-  NullLiteral: never[];
-  UndefinedLiteral: never[];
-  Hash: ['pairs'];
-  HashPair: ['value'];
-}
-
 export type NodeType = keyof Nodes;
 export type Node = Nodes[NodeType];
 

diff --git a/packages/@glimmer/syntax/lib/types/visitor-keys.ts b/packages/@glimmer/syntax/lib/types/visitor-keys.ts
@@ -1,31 +1,37 @@
-import { VisitorKeysMap } from './nodes';
+function tuple(): never[];
+function tuple<T extends string[]>(...args: T): T;
+function tuple<T>(...args: T[]): T[] {
+  return args;
+}
 
 // ensure stays in sync with typing
 // ParentNode and ChildKey types are derived from VisitorKeysMap
-const visitorKeys: VisitorKeysMap = {
-  Program: ['body'],
-  MustacheStatement: ['path', 'params', 'hash'],
-  BlockStatement: ['path', 'params', 'hash', 'program', 'inverse'],
-  ElementModifierStatement: ['path', 'params', 'hash'],
-  PartialStatement: ['name', 'params', 'hash'],
-  CommentStatement: [],
-  MustacheCommentStatement: [],
-  ElementNode: ['attributes', 'modifiers', 'children', 'comments'],
-  AttrNode: ['value'],
-  TextNode: [],
+const visitorKeys = {
+  Program: tuple('body'),
+  MustacheStatement: tuple('path', 'params', 'hash'),
+  BlockStatement: tuple('path', 'params', 'hash', 'program', 'inverse'),
+  ElementModifierStatement: tuple('path', 'params', 'hash'),
+  PartialStatement: tuple('name', 'params', 'hash'),
+  CommentStatement: tuple(),
+  MustacheCommentStatement: tuple(),
+  ElementNode: tuple('attributes', 'modifiers', 'children', 'comments'),
+  AttrNode: tuple('value'),
+  TextNode: tuple(),
 
-  ConcatStatement: ['parts'],
-  SubExpression: ['path', 'params', 'hash'],
-  PathExpression: [],
+  ConcatStatement: tuple('parts'),
+  SubExpression: tuple('path', 'params', 'hash'),
+  PathExpression: tuple(),
 
-  StringLiteral: [],
-  BooleanLiteral: [],
-  NumberLiteral: [],
-  NullLiteral: [],
-  UndefinedLiteral: [],
+  StringLiteral: tuple(),
+  BooleanLiteral: tuple(),
+  NumberLiteral: tuple(),
+  NullLiteral: tuple(),
+  UndefinedLiteral: tuple(),
 
-  Hash: ['pairs'],
-  HashPair: ['value'],
+  Hash: tuple('pairs'),
+  HashPair: tuple('value'),
 };
 
 export default visitorKeys;
+
+export type VisitorKeysMap = typeof visitorKeys;