False in logical conjunction causes missed null check

[joarwilk]

TypeScript Version: 3.9.2

Search Terms: false logical conjunction null

Expected behavior: Both statements should be valid

Actual behavior: One statement causes a typescript error

Code

const str: string | null = Math.random() > 0.5 ? "Hello World" : null;

const isfalse = false;

false && str && console.log(str.length) // Object (str) is possibly 'null'.
isfalse && str && console.log(str.length) // Valid

Output

"use strict";
const str = Math.random() > 0.5 ? "Hello World" : null;
const isfalse = false;
false && str && console.log(str.length);
isfalse && str && console.log(str.length);

Compiler Options

{
  "compilerOptions": {
    "noImplicitAny": true,
    "strictNullChecks": true,
    "strictFunctionTypes": true,
    "strictPropertyInitialization": true,
    "strictBindCallApply": true,
    "noImplicitThis": true,
    "noImplicitReturns": true,
    "alwaysStrict": true,
    "esModuleInterop": true,
    "declaration": true,
    "experimentalDecorators": true,
    "emitDecoratorMetadata": true,
    "moduleResolution": 2,
    "target": "ES2017",
    "jsx": "React",
    "module": "ESNext"
  }
}

Playground Link: Provided

Not the worst bug in the world and not very relevant for production scenarios, but interesting nonetheless.

[RyanCavanaugh]

Duplicate #26914