FP S3403: in JavaScript type of the initializer is considered

[vilchik-elena]

let x = true; // as there is no type in the declaration, the type of initializer is taken for the variable

if (cond) {
  x = "foo"; // compilation error should be produced by TypeScript
}

if (x === "foo") { // FP is reported here
  doSomething();
}

This issue mainly appears in JS code as TS code would not compile and we usually analyze valid code.

This is a problem in the way TypeScript compiler is working, so it's not clear how to approach this FP. One (not great) approach could be to disable the rule is there are diagnostics (compilation errors).

[vilchik-elena]

Reported in https://community.sonarsource.com/t/rule-falsely-claims-dissimilar-types-when-they-might-match/56330

[ilia-kebets-sonarsource]

Sames as https://github.com/SonarSource/SonarJS/issues/2819

[yassin-kammoun-sonarsource]

Closing since this is a duplicate.