read never assigned

Read but never assigned (read-never-assigned)

A project-wide lint rule: a field or a global variable that something READS but that nothing anywhere in the project ever assigns or creates. Every read sees the default value (0, nil, an empty string), so the read is either dead or a missing assignment -- typically an object field that is used (FList.Add(..)) but never constructed.

The per-file referenced-never-set checks private fields inside one unit; this rule checks every class field and every global, across the whole project, so it runs only where the whole index is in scope.

Running it from the CLI

drag-lint lint-all --db <project.sqlite>                              (ON by default)
drag-lint lint-all --db <project.sqlite> --rule read-never-assigned   (only this rule)
drag-lint lint-project --db <project.sqlite> --rule read-never-assigned
drag-lint lint-all --db <project.sqlite> --disable read-never-assigned

lint <file> does not run it by default: one unit cannot prove "never".

What counts as an assignment

Any one of these silences the symbol:

• X := v, Self.X := v, O.X := v, with O do X := v, a write in an initialization section;
• a hard cast TFoo(P).X := v (ref-gap G5);
• passing it where the callee takes it by var / out -- a project routine, a platform-library routine, an RTL intrinsic (SetLength, Inc, Val, Read, ...), or a callee neither index knows; when the resolver bound the call (Show(X), Obj.Show(X)), only THAT routine's own declaration (its overload set) decides; a same-named routine elsewhere -- e.g. ShlObj's IFileViewer.Show(var ...) -- no longer silences it. Only an unbound call (a late-bound Variant, an unknown receiver type) falls back to every project and library routine of that bare name, and then any var / out among them counts (silence, never a false finding);
• taking its address (@X);
• a property naming it as its write accessor;
• a global declared with an initialiser (G: Integer = 7), declared absolute, or the target of an absolute alias;
• an unbound ref of the same name that writes by any of the shapes above.

Never reported

Typed constants, record fields (a record is filled whole), published fields and the fields of a class's default-visibility section (the form loader streams them from the DFM).

Reviewing a finding

// dl:ok read-never-assigned -- <reason> on the declaration line.

What it needs

A project index (index --project); the platform library index sharpens the var / out answer for library callees.