Before You File a Bug Report Please Confirm You Have Done The Following...

• I have tried restarting my IDE and the issue persists.
• I have updated to the latest version of the packages.
• I havesearched for related issues and found none that matched my issue.
• I haveread the FAQ and my problem is not listed.

Playground Link

https://typescript-eslint.io/play/#ts=5.8.2&fileType=.ts&code=GYVwdgxgLglg9mABAUwB4EMC2AHANsgCgEpEBvAKEUXykVQG5LEZhECBZdKACwDoAndGAAmcTMUQA%2BRAFoAjCQpUqqRAF5EAJkZUAvk37IoIfklQBCRAGpEcxvvJoseQkUZA&eslintrc=N4KABGBECmAeAu0B2ATAzpAXGA2uCUADgDYCuA5gJZKYAC8AnodGgMYBOlh8AtC8dXgB6dtFYB7ALaTkKaCh6NmPVgAsxAa3mR8AXQA0%2BSO1LEWWMMAC%2BIK0A&tsconfig=N4KABGBEDGD2C2AHAlgGwKYCcDyiAuysAdgM6QBcYoEEkJemy0eFYDAruuGAL4g9A&tokens=false

Repro Code

functionexample(){letx;if(Math.random()>-1){x=2;}returnx!+1;}example();

ESLint Config

importtseslintfrom'typescript-eslint';exportdefaulttseslint.config(tseslint.configs.recommendedTypeChecked,{languageOptions:{parserOptions:{projectService:true,tsconfigRootDir:import.meta.dirname,},},},{files:['eslint.config.mjs'],extends:[tseslint.configs.disableTypeChecked],});

tsconfig

{"include": ["**/*.ts"],"compilerOptions": {"strict":true,            }}

Expected Result

No errors, since the non-null assertion (!)is necessary here; without it, tsc will refuse to compile the code, complaining that `'x' is possibly 'undefined'!

Actual Result

6:10  error  This assertion is unnecessary since it does not change the type of the expression  @typescript-eslint/no-unnecessary-type-assertion

Additional Info

Things that seem necessary to produce the error above:

• x is not explicitly typed when declared (so is implicitlyany)
• the initial assignment ofx takes place inside a conditional or a loop, and TypeScript therefore can't tell, without the non-null assertion, that the initial assignment is guaranteed to take place
• strict: true is enabled

The example code above is of course contrived, but a more realistic example where this would in fact be totally reasonable code would be one where, instead of anif (...) {...} that's guaranteed to run, the assignment takes place within aloop that's guaranteed to run (andx gets used to store some sort of information about the final iteration of the loop that gets used after the loop finishes).