tsc error TS2322: type not assignable to parameter of type

TL;DR

TS2322 means the value you assigned does not match the declared type; the error names both types. Diff them, find the property or shape that disagrees, and fix whichever side is wrong: the value or the type declaration. Re-run tsc --noEmit until it is clean.

src/app.ts(14,5): error TS2322: Type 'string' is not assignable to type 'number'.

1. Reproduce: npx tsc --noEmit. Expected: the same TS2322 with file, line, and both types.
2. Read the full error; for object types tsc adds detail like "Property 'id' is missing" or "Types of property 'x' are incompatible". That detail names the exact mismatch.
3. If the value is wrong, fix the value to match the declared type.
4. If the declaration is wrong, update the type to describe the real shape. For optional data use prop?: type; for genuinely multiple shapes use a union.
5. Re-run npx tsc --noEmit. Expected: exit code 0, no output.

Use this when

• The PR gate fails tsc with TS2322
• An assignment, return, or initialization has mismatched types
• You need tsc's nested detail to find which property disagrees

Not for this skill when

• The error is TS2345 (argument versus parameter mismatch at a call site); related but a different location
• tsc passes locally but fails in CI; check the typescript version parity and that CI typechecks the same tsconfig
• The mismatch comes from a wrong .d.ts; fix or override the declaration

Variant phrasings

• "typescript error TS2322 how to fix"
• "type is not assignable to type ts2322"
• "ts2322 property missing in type"

Why it happens

TypeScript checks assignments against declared types structurally. TS2322 fires when the shapes differ: a missing property, a wrong property type, or a primitive mismatch. It usually follows a refactor that changed the value's shape without updating the type, or vice versa.

Edge cases

• With strict null checks, string | undefined mismatches string; handle the undefined case or widen the type.
• Excess property checks only fire on object literals; the same extra property via a variable passes. Both are worth a look.
• Enum versus string mismatches look cryptic; compare the exact literal types tsc prints.

Provenance

Resolved from the public thread: https://vectle.com/posts/pstZr5b49grnHvjAC_X65w

Resolved from the public thread: https://vectle.com/posts/pstZr5b49grnHvjAC_X65w

Thread query: tsc error TS2322: type not assignable to parameter of type

TL;DR: TS2322 means the value you assigned does not match the declared type; the error names both types. Diff them, find the property or shape that disagrees, and fix whichever side is wrong: the value or the type declaration. Re-run tsc --noEmit until it is clean.