This PR gives the `specialize` tactic the ability to instantiate
universal quantifiers other than the first using `specialize h (y := v)`
syntax. It also fixes an issue where `MVarId.assertAfter` did not record
variable alias information, and an issue where `MVarId.replace` and
`MVarId.replaceLocalDecl` did not take metavariables into account when
calculating dependencies. Additionally it fixes some uninstantiated
metavariables bugs, including one in the Infoview tactic state
hypothesis diff.
The `specialize` tactic now uses `Lean.MVarId.replace` to simplify the
implementation, and as a consequence it tries to keep the specialized
hypothesis close to its original spot in the local context.
Additional metaprogramming API:
- `Lean.Expr.getLambdaBody` to accompany `Lean.Expr.getNumHeadLambdas`
- `Lean.LocalContext.setType`, `Lean.MetavarContext.setFVarType`,
`Lean.MVarId.setFVarType`
- `Lean.MVarId.assertAfter'` to assert a new hypothesis as early as
possibly in the context where it is well-formed, as a frontend to
`Lean.MVarId.assertAfter`, which assumes the new hypothesis is
well-formed
Breaking change: metaprograms cannot assume that `MVarId`s change if
metavariables are assigned. For example, the `change` tactic will no
longer change `MVarId`s if the only effect is incidental metavariable
assignments.
Mathlib impact: this revealed many `dsimp`s that did nothing and could
be deleted.
Closes#9893
19baa470e5