Type mismatch

[plantain-00]

TypeScript Version:

1.8.10

Code

function f(a: { b?: string; c?: number; }){
    // something else
}
f({b: ""}); //  no error as intended
f({b: 1}); //  error as intended
f(1); // expected: error, actually: no error
f(""); // expected: error, actually: no error

Expected behavior:
see comments in the code.
Actual behavior:
see comments in the code.

[malibuzios]

TypeScript currently treats all-optional types similarly to {} types (which are almost as weak as any in practice):

There have been past attempts to address this:

• One pull request dating back to July 2015, which was eventually closed: Weak type detection #3842
• Newer issue which is now labeled as 'Accepting PRs' with milestone of 'Community': All Optional Object Interface Converts to any #7485

[plantain-00]

Seems duplicate.
I searched as a key word "Type mismatch", but didn't find those.
I will close this issue, and focus on #7485.