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NilPy: Text as an attribute or base class binds the RTL file record

The collision

lib/pcl/tkinter.pas:302 declares Text = class(Widget). lib/rtl/textfile.pas:14 declares Text = record — standard Pascal's FILE type. One flat class namespace, first match wins, and the file record wins.

This is a live residue of [[bug-pascal-uses-is-transitive]], which is done. That fix is not enough for these two positions, which is the news here. The Pascal source of lib/pcl/tkhtmlview.pas knew about the collision and dodged it by hand — text_: TkTextWidget with the comment "the RTL's Text is a FILE record and wins an unqualified lookup outside tkinter". NilPy has no such alias to reach for, because the application writes the Python name.

What works and what does not — one cause, three faces

Canvas and Scrollbar are the controls: same façade, same positions, no RTL name collision, and they behave correctly throughout.

position Text control (Canvas/Scrollbar)
local / global — t = Text(root, …), t.insert(…) works works
instance attribute — self.t = Text(…) falls back to DYNAMIC statically typed
qualified attribute — self.t = tk.Text(…) compile error works
base class — class H(Text) / class H(tk.Text) wrong base works

The type is recorded correctly wherever it is resolved once and kept (a local), and incorrectly wherever it round-trips through the bare NAME (an attribute's inferred type, a base-class reference).

Face A — attribute becomes dynamic. self.text = Text(self, …) compiles, and direct calls work, because dynamic dispatch finds the façade method by name at run time. The proof it is dynamic rather than typed is the diagnostic, not a guess — an unknown method on each:

self.bar.nosuchmethod()   -> "Nil Python: Scrollbar has no method nosuchmethod"      (STATIC, closed world)
self.text.nosuchmethod()  -> "Nil Python: no class declares a method or callable
                              field .nosuchmethod()"                                 (DYNAMIC, searched everywhere)

The consequence is the one that matters: a bound method as a VALUE fails at run time off a dynamic receiver, while a direct call succeeds.

self.text.yview("moveto 0")            # works    — direct call, dynamic dispatch
self.bar.config(command=self.text.yview)   # AttributeError: 'Text' object has no attribute 'yview'

That second line is the canonical scrollbar wiring, so a scrolled Text cannot be expressed at all. The same line against a Canvas receiver works.

Face B — wrong base class. Both spellings, and the control beside it:

class H(Text):     ...   # "Nil Python: H has no method insert"
class H(tk.Text):  ...   # "Nil Python: H has no method insert"
class G(tk.Canvas): ...  # works: G().yview("moveto 0") runs

H inherits the file RECORD, which has no methods. This is the shape real tkhtmlview uses (HTMLScrolledText(ScrolledText) → Text), so it is not an exotic spelling.

Face C — qualified attribute is a compile error. self.foo = tk.Text(…) then self.foo.insert(…) gives Nil Python: Text has no method insert. Note the attribute NAME is irrelevant and was the first thing ruled out: self.foo fails, and self.text holding a Label is fine. It is the TYPE name.

from tkinter import Text silences face C but leaves face A — the attribute is still dynamic — so it is not a fix, only a quieter failure.

The diagnostic points at the healthy half

Worth fixing alongside, because it cost the most time here. The failure surfaces as:

AttributeError: 'Scrollbar' object has no attribute 'set'

Scrollbar.set is fine — it exists, and calling it directly works. The offending expression is self.text.yview in the other argument of the same statement. Anyone reading that message goes to the scrollbar, which is the one part of the pair that is healthy.

Repro

# tkscroll.npy — expected: prints ok; actual: AttributeError on Scrollbar.set
from tkinter import Frame, Scrollbar, Text
import tkinter as tk

class F(Frame):
    def __init__(self, master):
        super().__init__(master)
        self.bar = Scrollbar(self, orient="vertical")
        self.text = Text(self, width=20, height=3)
        self.text.configure(yscrollcommand=self.bar.set)
        self.bar.config(command=self.text.yview)      # <-- fails here
        self.bar.pack(side="right", fill="y")
        self.text.pack(side="left", fill="both", expand=True)

root = tk.Tk()
f = F(root); f.pack(); root.update()
print("ok")

Swap Text for Canvas (and drop wrap) and it runs — that is the control.

Scope of the damage

Any NilPy program that stores or subclasses a Text widget: every scrolled text view, every editor pane, and [[feature-b-tkhtmlview-in-nilpy]], which is blocked on this and cannot be written around — a Frame-based design needs text.yview as a value (face A) and a Text-based design needs the base class (face B). ~/songformatter reaches it through tkhtmlview.

Not a façade gap, and not fixable in lib/pcl. Track B cannot rename tkinter.Text (the application writes the Python name) nor textfile.Text (standard Pascal's file type). The alias TkTextWidget = Text already exists at tkinter.pas:565 for the Pascal side and is unreachable from Python.

Fix direction — for whoever holds Track A

Make the two by-name positions carry the RESOLVED class the way a local does, rather than re-looking-up the bare name. The ordering subtleties are the ones [[decide-class-namespace-scoping]] and bug-nilpy-stdlib-name-binds-pascal-unit already record; this ticket adds that a record and a class can collide, not just two classes, and that a Text record silently wins over a Text class.

Found alongside, already fixed (Track B, not part of this ticket)

Text had no yview / xview / yview_scroll in lib/pcl/tkinter.pas at all — Canvas has carried them since it was written. Added, and verified from Pascal where a missing method is a hard compile error. That gap is real and independent, but it is NOT the cause here: with it fixed, the direct call self.text.yview("moveto 0") works and the bound-method-as-value still fails.

There is already a test for this invariant — it just uses Canvas

examples/tk/field_class_identity.npy (in make test-nilpy) opens with:

A field assigned a QUALIFIED construction keeps its class — in any method, not only __init__ — so calls on it resolve statically and bind keyword arguments.

That is exactly face A, asserted and passing. It passes because every field in it is a Canvas or a Frame. The invariant it defends is false for Text, and the suite cannot see that because no case picks a name the RTL also uses.

So the cheap regression is a sibling case in that same file — a field assigned tk.Text(...), plus one class H(tk.Text) — and it is worth adding whatever else is done here, because a colliding name is the one thing the existing test was never pointed at.

Gate

The repro above printing ok; class H(tk.Text) inheriting insert; make test-nilpy green; self-host byte-identical. Add the Text cases to field_class_identity.npy per the section above — this survived a done root fix unnoticed precisely because nothing tested a colliding name.

Resolution (2026-08-11) — one predicate, and the helper was already written

The repro does not need tkinter, X11 or a display

Before touching anything, the collision was reduced to a 12-line Pascal unit and 6 lines of NilPy — a Text = class next to the RTL's Text = record, no widgets involved. That made the edit/measure loop seconds instead of a headless X server, and it gave a control that removes the variable rather than relabelling it: the identical unit with the class renamed Zext.

Text (collides) Zext (control)
before attribute dynamic, class H(Text) → "H has no method Insert" both fine
after attribute: 15 / base class: 17 11 identical

The root — IsClassType asked the wrong ROW

ci := FindUClass(lo2);                          { the FIRST row of that name }
if (ci >= 0) and (not UClsIsRecord[ci]) then Result := True;

FindUClass answers with the first row whatever it is, so testing not UClsIsRecord[ci] on it says False whenever a same-named record comes first — even though a class of that name also exists. The RTL's Text sits ahead of lib/pcl's Text = class(Widget), so IsClassType('Text') was False and every gate keyed on it stood down. That is the ticket's "one cause, three faces", and it is one line.

The helper for it already existed, wired to only three sites

FindUClassNonRecord (symtab.inc:1171) — "the CLASS of that name, skipping same-named RECORDS" — was written for this exact Text collision, cites decide-class-namespace-scoping, and its comment names the file record. It had been wired into the construction intercept and the Pascal typecast branch. The positions this ticket reports were left on plain FindUClass:

site face
IsClassType (symtab.inc) the root predicate under all three
PyParseClass base-class lookup B — inherited the record
the hoisted base-class lookup B — the same, on the pre-pass path
PyRecFromTokenIndex A — the field's recorded type
the qualified-construction arm (self.t = tk.Text(...)) C — compile error
the annotation arm beside IsClassType the ci disagreeing with the predicate that just said yes

Textbook normalise-dont-special-case.md: the fix existed, and the siblings were never grepped for. Six sites now share one rule.

Verified

Regression test — in the file that was already asserting this

Per the ticket's own section, the cases went into examples/tk/field_class_identity.npy rather than a new file: it has asserted this invariant since it was written and could not see the break, because every field in it was a Canvas or a Frame — a name nothing else uses. Added: a field from bare Text(...) and from qualified tk.Text(...) (separate lookups, both were broken), a bound method taken as a value off that field (the thing a dynamic receiver could not do, while a direct call on it worked — so a direct call alone would not have caught it), and class Editor(tk.Text).

Confirmed it fails on the old compiler, which is what makes it a regression test rather than a passing example: stable_linux_amd64/default/pinned reports "Nil Python: Text has no method configure" on it, and HEAD compiles it.

Gate: tools/gate.sh quick GREEN (self-host fixedpoint + FPC seed canary) + make test-nilpy.

Log