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Bug: Boolean type literals misbehaving #10432

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@benjamin-hodgson

Description

@benjamin-hodgson

TypeScript Version: nightly (2.1.0-dev.20160818)

Code
I lifted this from Anders's final example in #9407 (comment).

type Result<T> = { success: true, value: T } | { success: false };

function foo(): Result<number> {
    if (someTest()) {
        return { success: true, value: 42 };
    }
    else {
        return { success: false };
    }
}
function someTest(): Boolean { return true; }

Expected behavior:
Type-checks OK

Actual behavior:
Type error:

result.ts(5,16): error TS2322: Type '{ success: boolean; value: number; }' is not assignable to type 'Result<number>'.
  Type '{ success: boolean; value: number; }' is not assignable to type '{ success: false; }'.
    Types of property 'success' are incompatible.
      Type 'boolean' is not assignable to type 'false'.
result.ts(8,16): error TS2322: Type '{ success: boolean; }' is not assignable to type 'Result<number>'.
  Type '{ success: boolean; }' is not assignable to type '{ success: false; }'.
    Types of property 'success' are incompatible.
      Type 'boolean' is not assignable to type 'false'.

If I add manual type annotations (true as true, false as false) to the success assignments it works:

function foo(): Result<number> {
    if (someTest()) {
        return { success: true as true, value: 42 };
    }
    else {
        return { success: false as false };
    }
}

The bug only affects Boolean literals. If I use enum, number, or string type literals it works - for example:

type Result<T> = { success: 1, value: T } | { success: 0 };

function foo(): Result<number> {
    if (someTest()) {
        return { success: 1, value: 42 };
    }
    else {
        return { success: 0 };
    }
}

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