Struct SuppressedTabMarks 

pub struct SuppressedTabMarks(/* private fields */);

Disables tab marks for the lifetime of the guard, restoring the previous count on drop — tex.web §394 macro_call:

align_state:=1000000; {disable tab marks, etc.}

TeX suppresses & and \cr while it scans a macro’s parameters, so a tab mark inside an argument is an ordinary token. Without that, a & in a delimiter-fenced argument reaches the alignment as a cell break: for \mqty( b_0 &0 \\ 0 &b_1 ) (physics.sty, witness 2605.05903) the row splits mid-argument and the alignment then cannot close its own group — Error:unexpected:\lx@begin@alignment Attempt to close a group that switched to mode restricted_horizontal — truncating the rest of the document. The brace form \mqty{…} was always safe because cell scanning skips balanced groups; (…) is not a group. Perl raises the identical error (11 of them on the 14-line repro), so this is beyond-Perl and pdflatex, which renders the repro silently, is the ground truth.

Only armed inside an alignment: outside one there are no tab marks to suppress, which keeps this off the hot path for every ordinary macro call. 28 papers of the 2026-07-29 bibliography-absence residual truncate here.

Implementations

impl SuppressedTabMarks

pub fn for_argument_scan() -> Self

Trait Implementations

impl Drop for SuppressedTabMarks

fn drop(&mut self)

Executes the destructor for this type.

fn pin_drop(self: Pin<&mut Self>)

🔬This is a nightly-only experimental API. (pin_ergonomics)

Execute the destructor for this type, but different to Drop::drop, it requires self to be pinned.