Compilation exception in mapped type

[zamb3zi]

TypeScript Version: nightly (2.2.0-dev.20161219)

Code

type Foo<T, F extends keyof T> = {
    pf: {[P in F]?: T[P]},
    pt: {[P in T]?: T[P]}, // note: should be in keyof T
};
type O = {x: number, y: boolean};
let o: O = {x: 5, y: false};
let f: Foo<O, 'x'> = {
    pf: {x: 7},
    pt: {x: 7, y: false},
};

Expected behavior:

Compiling only the first type declaration produces the following expected error:

$ node node_modules/typescript/bin/tsc test.ts
test.ts(4,16): error TS2322: Type '{}' is not assignable to type 'string'.
test.ts(4,21): error TS2536: Type 'P' cannot be used to index type 'T'.

Actual behavior:
Compiling the whole example with a clean nightly install without tsconfig produces:

$ node node_modules/typescript/bin/tsc test.ts
C:\Users\...\Documents\TCM\git\tmp\node_modules\typescript\lib\tsc.js:49834
                throw e;
                ^

TypeError: Cannot read property 'flags' of undefined
    at getModifiersTypeFromMappedType (C:\Users\...\Documents\TCM\git\tmp\node_modules\typescript\lib\tsc.js:23125:60)
    at resolveMappedTypeMembers (C:\Users\...\Documents\TCM\git\tmp\node_modules\typescript\lib\tsc.js:23068:49)
    at resolveStructuredTypeMembers (C:\Users\...\Documents\TCM\git\tmp\node_modules\typescript\lib\tsc.js:23153:25)
    at getPropertyOfType (C:\Users\...\Documents\TCM\git\tmp\node_modules\typescript\lib\tsc.js:23307:32)
    at C:\Users\...\Documents\TCM\git\tmp\node_modules\typescript\lib\tsc.js:28345:47
    at applyToContextualType (C:\Users\...\Documents\TCM\git\tmp\node_modules\typescript\lib\tsc.js:28321:24)
    at getTypeOfPropertyOfContextualType (C:\Users\...\Documents\TCM\git\tmp\node_modules\typescript\lib\tsc.js:28344:20)
    at getContextualTypeForObjectLiteralElement (C:\Users\...\Documents\TCM\git\tmp\node_modules\typescript\lib\tsc.js:28368:40)
    at getContextualType (C:\Users\...\Documents\TCM\git\tmp\node_modules\typescript\lib\tsc.js:28442:28)
    at checkExpressionForMutableLocation (C:\Users\...\Documents\TCM\git\tmp\node_modules\typescript\lib\tsc.js:31213:69)