error on variables that are used but never initialized (#55887)

Co-authored-by: Daniel Rosenwasser <DanielRosenwasser@users.noreply.github.com>

src/compiler/types.ts

@@ -5970,7 +5970,7 @@ export interface Symbol {
     /** @internal */ exportSymbol?: Symbol; // Exported symbol associated with this symbol
     /** @internal */ constEnumOnlyModule: boolean | undefined; // True if module contains only const enums or other modules with only const enums
     /** @internal */ isReferenced?: SymbolFlags; // True if the symbol is referenced elsewhere. Keeps track of the meaning of a reference in case a symbol is both a type parameter and parameter.
-    /** @internal */ lastAssignmentPos?: number; // Source position of last node that assigns value to symbol
+    /** @internal */ lastAssignmentPos?: number; // Source position of last node that assigns value to symbol. Negative if it is assigned anywhere definitely
     /** @internal */ isReplaceableByMethod?: boolean; // Can this Javascript class property be replaced by a method symbol?
     /** @internal */ assignmentDeclarationMembers?: Map<number, Declaration>; // detected late-bound assignment declarations associated with the symbol
 }