pmacs-gpu/src/math_parse.rs — the Q#MS2 subset: characters, groups,
sub/superscripts in either order, and \frac, plus the Greek seed map.
Everything outside the subset is a typed error, which Q#MS8 turns into
"render the raw source".
The AST is semantic, not presentational: \alpha resolves to 'α' here, but the
math-italic mapping stays in layout, where a codepoint becomes a glyph.
Baking italics into the AST would make the tree disagree with the source and
would have to be unpicked by any later non-italic style context.
Two bugs the tests caught before they could reach layout, both from skipping
whitespace in the wrong place. `parse_atom` consumed it, but the ^/_ dispatch
happens in `parse_sequence` BEFORE atoms are read — so `x ^ 2` parsed the
caret as a literal character, and an all-whitespace span produced an empty
group instead of the Empty error. Whitespace is now skipped at the dispatch
point, which fixes both at one seam.
Interior `$` is rejected explicitly so `$$x$$` degrades through the error path
(acceptance 15) rather than half-rendering.
Clippy reports MathNode as dead code, which is correct and expected: the
parser has no consumer until Tier 3 layout lands. That is exactly the
condition Q#LX5 refused to ship, now enforced mechanically. It is not
suppressed; it clears when layout arrives in this same branch.
11 unit tests, no GPU or font required.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Levi Neuwirth
b9aed61e23