tests/cases/compiler/numericIndexerTyping2.ts(9,5): error TS2322: Type 'Date' is not assignable to type 'string'. tests/cases/compiler/numericIndexerTyping2.ts(12,5): error TS2322: Type 'Date' is not assignable to type 'string'. ==== tests/cases/compiler/numericIndexerTyping2.ts (2 errors) ==== class I { [x: string]: Date } class I2 extends I { } var i: I; var r: string = i[1]; // error: numeric indexer returns the type of the string indexer ~ !!! error TS2322: Type 'Date' is not assignable to type 'string'. var i2: I2; var r2: string = i2[1]; // error: numeric indexer returns the type of the string indexere ~~ !!! error TS2322: Type 'Date' is not assignable to type 'string'.