Make cgen/seq for lists be used more often.
Correctly instantiate poly dots during inference.

This removes the need for the cache of type variables for instantiating
dotted variables, because we instantiate the uses at once.

Closes PR 14576.
Closes PR 14577.
Closes PR 14579.
Closes PR 14580.
avoid re-generating some bitmaps on test
move some test-generated files to temp dir
raco test: handling of spurious files

A `--drdr` run shouldn't stop because a discoevered file
disappears (such as one generated temporarily by a test).

Also, use new style for some errors.
raco test: add `--heartbeat` flag

Useful when running many tests in parallel to keep track of a test
that is running especially long (and maybe stuck).
bitwise-bit-field: repair fixnum overflow problems

Bug reported by Roman Klochkov
add to the framework's spell checking support

the ability to determine if specific spots in the editor correspond to
misspelled words
improve drracket to offer spelling suggestions and to jump to next misspelled word
optimizer: reduce constants to #t/#f in boolean contexts

While something like `(if 7 e1 e2)` was already reduced to `e1`,
this improvement makes `(if (let ([x (random)]) 7) e1 e2)`
reduce to `(if (let ([x (random)]) #t) e1 e2)`.
optimizer: local known to satisfy predicate => #t in a boolean context

For example, `(if (pair? x) (if x e1 e2) e3)` => `(if (pair? x) e1 e3)`.
optimizer: unwrap `let` and `begin` around constant test in `if`

Takes advantage of Gustavo's improvements
redex: refactor benchmark plotting

- add sane interface for points plot
- add the line plot
fix bitmap rotate/flip interaction

closes PR 14585
adjust render-metafunction docs
redex: adjust benchmark contracts and provides
Readline-to-Racket: Rename file to mzrl.rkt to rktrl.rkt
Make type of make-vector more precise.

Before that, ((inst make-vector Natural) 10) would return a (Vectorof
Integer) which is bad.

Thanks to Alexander Knauth for the suggestion!
Make TypeFilter and NotTypeFilter have a Path as a subcomponent.

This changes Filters to have a Path as a subcomponent instead of having
the list of Path-Elems and name-ref/c separately. This is part of the
rework to have better object support.
optimizer: add missing "else"

Thanks to David Vanderson