JSDoc:Object<string, T> creates index signature

And `Object<number, T>` creates a numeric index signature. Other uses
still create `any` as before.

src/compiler/checker.ts

@@ -6872,6 +6872,17 @@ namespace ts {
 
         function getPrimitiveTypeFromJSDocTypeReference(node: TypeReferenceNode): Type {
             if (isIdentifier(node.typeName)) {
+                if (node.typeName.text === "Object") {
+                    if (node.typeArguments && node.typeArguments.length === 2) {
+                        const from = getTypeFromTypeNode(node.typeArguments[0]);
+                        const to = getTypeFromTypeNode(node.typeArguments[1]);
+                        let index = createIndexInfo(to, /*isReadonly*/ false);
+                        if (from === stringType || from === numberType) {
+                            return createAnonymousType(undefined, emptySymbols, emptyArray, emptyArray, from === stringType ? index : undefined, from === numberType ? index : undefined)
+                        }
+                    }
+                    return anyType;
+                }
                 switch (node.typeName.text) {
                     case "String":
                         return stringType;
@@ -6885,8 +6896,6 @@ namespace ts {
                         return undefinedType;
                     case "Null":
                         return nullType;
-                    case "Object":
-                        return anyType;
                     case "Function":
                     case "function":
                         return globalFunctionType;

tests/baselines/reference/jsdocIndexSignature.symbols

@@ -0,0 +1,13 @@
+=== tests/cases/conformance/jsdoc/indices.js ===
+/** @type {Object.<string, number>} */
+var o1;
+>o1 : Symbol(o1, Decl(indices.js, 1, 3))
+
+/** @type {Object.<number, boolean>} */
+var o2;
+>o2 : Symbol(o2, Decl(indices.js, 3, 3))
+
+/** @type {Object.<boolean, string>} */
+var o3;
+>o3 : Symbol(o3, Decl(indices.js, 5, 3))
+

tests/baselines/reference/jsdocIndexSignature.types

@@ -0,0 +1,13 @@
+=== tests/cases/conformance/jsdoc/indices.js ===
+/** @type {Object.<string, number>} */
+var o1;
+>o1 : { [x: string]: number; }
+
+/** @type {Object.<number, boolean>} */
+var o2;
+>o2 : { [x: number]: boolean; }
+
+/** @type {Object.<boolean, string>} */
+var o3;
+>o3 : any
+

tests/cases/conformance/jsdoc/jsdocIndexSignature.ts

@@ -0,0 +1,10 @@
+// @allowJs: true
+// @checkJs: true
+// @noEmit: true
+// @Filename: indices.js
+/** @type {Object.<string, number>} */
+var o1;
+/** @type {Object.<number, boolean>} */
+var o2;
+/** @type {Object.<boolean, string>} */
+var o3;