See Section "Other goodies" at
https://github.com/leanprover/lean/wiki/Refactoring-structures
This commit also improves the support for projections in the
unifier/matcher.
Now, we consider the extra case-split for projections.
Given a projection `proj`, and the constraint `proj s =?= proj t`, we need to try first `s =?= t` and if it fails, then try to reduce.
This is needed in the standard library because we now have constraints such as:
```
@has_le.le ?A ?s ?a ?b =?= @has_le.le nat nat.has_add x y
```
If we reduce the right hand side, we get the unsolvable constraint
```
@has_le.le ?A ?s ?a ?b =?= nat.le x y
```
Before this change, the constraint was `@le ?A ?s ?a ?b =?= @le nat nat.has_add x y`, and we already perform a case-split in this case.
Moreover, projections were eagerly reduced whenever possible.
The extra case-split generates a performance problem in several tests. For example `fib 8 = 34` was timing out.
I worked around this issue by performing the case-split only when the constraint contains meta-variables.
There are also minor issues. Example. `<` is notation for `has_lt.lt`, but `>` is for `gt`.
@kha I had to add yet another hack to fix this issue.
In notation declarations, names are resolved at notation declaration time.
So, users do not expect them to be resolved again at tactic execution time.
I addressed this problem by wrapping constants occurring in notation
declarations with a "frozen_name" annotation. This transformation is
only performed if m_in_quote is true.
Then resolve_names_fn at elaborator.cpp will not try to resolve the
names again.
This change broke two other modules. `-` notation for inverting
equations at `rw`, and `calc` expressions inside quotes.
The broke for the same reason. They were not expecting the constants
to be wrapped with an annotation.
Summary:
We minimize the number of "'sorry' used warning messages". We also
re-target the error to the main declaration. Example: foo._main ==> foo
We do not report for auxiliary declarations such as "_example" and
"foo.equations._eqn_1"
Get rid of the redundant error message "error : failed" for tactics.
We added "silent failures" in the tactic framework.
We do not store line/col information for tactics nested in notation
declarations. Before this commit, we would have tactics such
as (tactic.save_info line col) nested inside of notation declarations.
