This implements the `termination_by structural` syntax proposed in
#3909.
I went with `termination_by structural` over, say,
`termination_by (config := {method := .structural})` mainly because it
was
easier to get going (otherwise I’d have to look into how to define
recursive
parsers, as `Parser.config` depends on `term` and `termination_by` is
part of
term. But also because I find it more ergonomic and aesthetic as a user.
But syntax can still change.
The `termination_by?` syntax will no longer force well-founded
recursion,
and instead the inferred `termination_by structurally` annotation will
be shown
if structural termination is possible.
While I was it, this fixes#4546 the easy way (log errors about but
otherwise
ignore incomplete `termination_by` sets for mutual recursion). Maybe we
get
multiple replacements (#4551), but even then this this good behavior.
Involves a bit of shuffling around `TerimationHints` (now validated for
a
clique already by `PreDefinition.main`) and `TerminationArguments` (now
lifted
out of the `WF` namespace, and a bit simplified).
Fixes#3909
---------
Co-authored-by: Richard Kiss <him@richardkiss.com>
This is the groundwork for a tactic index in generated documentation, as
there was in Lean 3. There are a few challenges to getting this to work
well in Lean 4:
* There's no natural notion of *tactic identity* - a tactic may be
specified by multiple syntax rules (e.g. the pattern-matching version of
`intro` is specified apart from the default version, but both are the
same from a user perspective)
* There's no natural notion of *tactic name* - here, we take the
pragmatic choice of using the first keyword atom in the tactic's syntax
specification, but this may need to be overridable someday.
* Tactics are extensible, but we don't want to allow arbitrary imports
to clobber existing tactic docstrings, which could become unpredictable
in practice.
For tactic identity, this PR introduces the notion of a *tactic
alternative*, which is a `syntax` specification that is really "the same
as" an existing tactic, but needs to be separate for technical reasons.
This provides a notion of tactic identity, which we can use as the basis
of a tactic index in generated documentation. Alternative forms of
tactics are specified using a new `@[tactic_alt IDENT]` attribute,
applied to the new tactic syntax. It is an error to declare a tactic
syntax rule to be an alternative of another one that is itself an
alternative. Documentation hovers now take alternatives into account,
and display the docs for the canonical name.
*Tactic tags*, created with the `register_tactic_tag` command, specify
tags that may be applied to tactics. This is intended to be used by
doc-gen and Verso. Tags may be applied using the `@[tactic_tag TAG1 TAG2
...]` attribute on a canonical tactic parser, which may be used in any
module to facilitate downstream projects introducing tags that apply to
pre-existing tactics. Tags may not be removed, but it's fine to
redundantly add them. The collection of tags, and the tactics to which
they're applied, can be seen using the `#print tactic tags` command.
*Extension documentation* provides a structured way to document
extensions to tactics. The resulting documentation is gathered into a
bulleted list at the bottom of the tactic's docstring. Extensions are
added using the `tactic_extension TAC` command. This can be used when
adding new interpretations of a tactic via `macro_rules`, when extending
some table or search index used by the tactic, or in any other way. It
is a command to facilitate its flexible use with various extension
mechanisms.
Extends Lean's incremental reporting and reuse between commands into
various steps inside declarations:
* headers and bodies of each (mutual) definition/theorem
* `theorem ... := by` for each contained tactic step, including
recursively inside supported combinators currently consisting of
* `·` (cdot), `case`, `next`
* `induction`, `cases`
* macros such as `next` unfolding to the above
*Incremental reuse* means not recomputing any such steps if they are not
affected by a document change. *Incremental reporting* includes the
parts seen in the recording above: the progress bar and messages. Other
language server features such as hover etc. are *not yet* supported
incrementally, i.e. they are shown only when the declaration has been
fully processed as before.
---------
Co-authored-by: Scott Morrison <scott.morrison@gmail.com>
To eliminate parsing differences between Windows and other platforms,
the frontend now normalizes all CRLF line endings to LF, like [in
Rust](https://github.com/rust-lang/rust/issues/62865).
Effects:
- This makes Lake hashes be faithful to what Lean sees (Lake already
normalizes line endings before computing hashes).
- Docstrings now have normalized line endings. In particular, this fixes
`#guard_msgs` failing multiline tests for Windows users using CRLF.
- Now strings don't have different lengths depending on the platform.
Before this PR, the following theorem is true for LF and false for CRLF
files.
```lean
example : "
".length = 1 := rfl
```
Note: the normalization will take `\r\r\n` and turn it into `\r\n`. In
the elaborator, we reject loose `\r`'s that appear in whitespace. Rust
instead takes the approach of making the normalization routine fail.
They do this so that there's no downstream confusion about any `\r\n`
that appears.
Implementation note: the LSP maintains its own copy of a source file
that it updates when edit operations are applied. We are assuming that
edit operations never split or join CRLFs. If this assumption is not
correct, then the LSP copy of a source file can become slightly out of
sync. If this is an issue, there is some discussion
[here](https://github.com/leanprover/lean4/pull/3903#discussion_r1592930085).
even when rewriting the type of `h` becuase there is no expected type.
(When there is an expected type, it already tried both orientations.)
Also feeble attempt to include this information in the docstring without
writing half a manual chapter.
Go-to-def on `@[builtin_term_parser]` should go to the line
```lean
builtin_initialize registerBuiltinParserAttribute `builtin_term_parser ``Category.term
```
not
```lean
/-- `term` is the builtin syntax category for terms. ... -/
def term : Category := {}
```
While implementing #3925, I noticed that the performance of the
`textDocument/semanticTokens/full` request is *extremely* bad due to a
quadratic implementation. Specifically, on my machine, computing the
full semantic tokens for `Lean/Elab/Do.lean` took a full 5s. In
practice, this means that while elaborating the file, one core is
entirely busy with computing the semantic tokens for the file.
This PR fixes this performance bug by re-implementing the semantic token
handling, reducing the latency for `Lean/Elab/Do.lean` from 5s to 60ms.
As a result, the overly cautious refresh latency of 5s in #3925 can
easily be reduced to 2s again.
Since the previous semantic tokens implementation used a very brittle
hack to identify projections, this PR also changes the projection
notation elaboration to augment the `InfoTree` syntax for the field of a
projection with a special syntax node of kind
`Lean.Parser.Term.identProjKind`. With this syntax kind, projection
fields can now easily be identified in the `InfoTree`.
This fixes an issue where the completion would use info nodes before the
cursor for computing completions.
Fixes https://github.com/leanprover/lean4/issues/3462.
ToDo:
- [x] Fix test failures for completions that previously worked by
accident (cc: @Kha)
- [x] stage0 update
---------
Co-authored-by: Sebastian Ullrich <sebasti@nullri.ch>
Commands that can optionally parse an `ident` or parse any number of
`ident`s generally should require that the `ident` use `colGt`. This
keeps typos in commands from being interpreted as identifiers.
For example, without this rule,
```
universe u
Open Lean
````
parses the same as `universe u Open Lean`. It would be better to get an
error on `Open`.
This PR adds `checkColGt` to `section`, `namespace`, `end`, `variable`,
and `universe`.
Closes#2684
This coercion caused difficult-to-diagnose bugs sometimes. Because there
are some situations where converting a string to a name should be done
by parsing the string, and others where it should not, an explicit
choice seems better here.
---------
Co-authored-by: Mac Malone <tydeu@hatpress.net>
This adds the concept of **functional induction** to lean.
Derived from the definition of a (possibly mutually) recursive function,
a **functional
induction principle** is tailored to proofs about that function. For
example from:
```
def ackermann : Nat → Nat → Nat
| 0, m => m + 1
| n+1, 0 => ackermann n 1
| n+1, m+1 => ackermann n (ackermann (n + 1) m)
derive_functional_induction ackermann
```
we get
```
ackermann.induct (motive : Nat → Nat → Prop) (case1 : ∀ (m : Nat), motive 0 m)
(case2 : ∀ (n : Nat), motive n 1 → motive (Nat.succ n) 0)
(case3 : ∀ (n m : Nat), motive (n + 1) m → motive n (ackermann (n + 1) m) → motive (Nat.succ n) (Nat.succ m))
(x x : Nat) : motive x x
```
At the moment, the user has to ask for the functional induction
principle explicitly using
```
derive_functional_induction ackermann
```
The module docstring of `Lean/Meta/Tactic/FunInd.lean` contains more
details on the
design and implementation of this command.
More convenience around this (e.g. a `functional induction` tactic) will
follow eventually.
This PR includes a bunch of `PSum`/`PSigma` related functions in the
`Lean.Tactic.FunInd`
namespace. I plan to move these to `PackArgs`/`PackMutual` afterwards,
and do some cleaning
up as I do that.
---------
Co-authored-by: David Thrane Christiansen <david@davidchristiansen.dk>
Co-authored-by: Leonardo de Moura <leomoura@amazon.com>
the user can now write `termination_by?` to see the termination argument
inferred by GuessLex, and turn it into `termination_by …` using the “Try
this” widget or a code action.
To be done later, maybe: Avoid writing `sizeOf` if it's not necessary.
When editing core Lean, the `pp.proofs` feature causes goal states to fail to display in the Infoview, instead showing only "error when printing message: unknown constant '«term⋯»'". This PR moves the `⋯` syntax from Init.NotationExtra to Lean.Elab.BuiltinTerm
It also makes it so that `⋯` elaborates as `_` while logging a warning, rather than throwing an error, which should be somewhat more friendly when copy/pasting from the Infoview.
Closes#3476
The `decide` tactic produces error messages that users find to be
obscure. Now:
1. If the `Decidable` instance reduces to `isFalse`, it reports that
`decide` failed because the proposition is false.
2. If the `Decidable` instance fails to reduce, it explains what
proposition it failed for, and it shows the reduced `Decidable` instance
rather than the `Decidable.decide` expression. That expression tends to
be less useful since it shows the unreduced `Decidable` argument (plus
it's a lot longer!)
Examples:
```lean
example : 1 ≠ 1 := by decide
/-
tactic 'decide' proved that the proposition
1 ≠ 1
is false
-/
opaque unknownProp : Prop
open scoped Classical in
example : unknownProp := by decide
/-
tactic 'decide' failed for proposition
unknownProp
since its 'Decidable' instance reduced to
Classical.choice ⋯
rather than to the 'isTrue' constructor.
-/
```
When reporting the error, `decide` only shows the whnf of the
`Decidable` instance. In the future we could consider having it reduce
all decidable instances present in the term, which can help with
determining the cause of failure (this was explored in
8cede580690faa5ce18683f168838b08b372bacb).
Adds a simple error-recovery mechanism to Lean's parser, similar to
those used in other combinator parsing libraries.
Lean itself isn't very amenable to error recovery with this mechanism,
as it requires global knowledge of the grammar in question to write
recovery rules that don't break backtracking or `<|>`. I only found a
few opportunities.
But for DSLs, this is really important. In particular, Verso parse
errors interacted very badly with Lean parse errors in a way that
required frequent "restart file" commands, but this mechanism allows me
to both recover from Verso parse errors and to have Lean skip the rest
of the file rather than repeatedly trying to parse it as Lean commands.
This is not a complete upstreaming of that file (it also supports `∀ᵉ (x
< 2) (y < 3), p x y` as shorthand for `∀ x < 2, ∀ y < 3, p x y`, but I
don't think we need this; it is used in Mathlib).
Syntaxes still need to be made built-in.
---------
Co-authored-by: Leonardo de Moura <leomoura@amazon.com>
This change
* moves `termination_by` and `decreasing_by` next to the function they
apply to
* simplify the syntax of `termination_by`
* apply the `decreasing_by` goal to all goals at once, for better
interactive use.
See the section in `RELEASES.md` for more details and migration advise.
This is a hard breaking change, requiring developers to touch every
`termination_by` in their code base. We decided to still do it as a
hard-breaking change, because supporting both old and new syntax at the
same time would be non-trivial, and not save that much. Moreover, this
requires changes to some metaprograms that developers might have
written, and supporting both syntaxes at the same time would make
_their_ migration harder.
