feat(language-service): completions support for tuple array (#33928)

PR Close #33928

packages/language-service/src/expression_type.ts

@@ -241,7 +241,8 @@ export class AstType implements AstVisitor {
   visitKeyedRead(ast: KeyedRead): Symbol {
     const targetType = this.getType(ast.obj);
     const keyType = this.getType(ast.key);
-    const result = targetType.indexed(keyType);
+    const result = targetType.indexed(
+        keyType, ast.key instanceof LiteralPrimitive ? ast.key.value : undefined);
     return result || this.anyType;
   }
 

packages/language-service/src/symbols.ts

@@ -116,9 +116,12 @@ export interface Symbol {
 
   /**
    * Return the type of the expression if this symbol is indexed by `argument`.
+   * Sometimes we need the key of arguments to get the type of the expression, for example
+   * in the case of tuples (`type Example = [string, number]`).
+   * [string, number]).
    * If the symbol cannot be indexed, this method should return `undefined`.
    */
-  indexed(argument: Symbol): Symbol|undefined;
+  indexed(argument: Symbol, key?: any): Symbol|undefined;
 }
 
 /**
@@ -349,4 +352,4 @@ export interface SymbolQuery {
    * Return the span of the narrowest non-token node at the given location.
    */
   getSpanAt(line: number, column: number): Span|undefined;
-}
+}

packages/language-service/src/typescript_symbols.ts

@@ -284,7 +284,7 @@ class TypeWrapper implements Symbol {
     return selectSignature(this.tsType, this.context, types);
   }
 
-  indexed(argument: Symbol): Symbol|undefined {
+  indexed(argument: Symbol, value: any): Symbol|undefined {
     const type = argument instanceof TypeWrapper ? argument : argument.type;
     if (!(type instanceof TypeWrapper)) return;
 
@@ -292,7 +292,14 @@ class TypeWrapper implements Symbol {
     switch (typeKind) {
       case BuiltinType.Number:
         const nType = this.tsType.getNumberIndexType();
-        return nType && new TypeWrapper(nType, this.context);
+        if (nType) {
+          // get the right tuple type by value, like 'var t: [number, string];'
+          if (nType.isUnion()) {
+            return new TypeWrapper(nType.types[value], this.context);
+          }
+          return new TypeWrapper(nType, this.context);
+        }
+        return undefined;
       case BuiltinType.String:
         const sType = this.tsType.getStringIndexType();
         return sType && new TypeWrapper(sType, this.context);