From e559dfc4995ae6777d9ff07d34db738cb77a519c Mon Sep 17 00:00:00 2001
From: Hugo Herbelin
Date: Tue, 4 Feb 2020 18:40:24 +0100
Subject: Adding an alias "pose proof (x:=a)" for "pose proof a as x".

This is to be consistent with "pose (x:=a)" (and an alternative to
"assert (x:=a)").

This was suggested by
"https://github.com/HoTT/HoTT/pull/1208#discussion_r374342962".
---
 .../04-tactics/11522-master+pose-proof-wo-as-syntax.rst     |  6 ++++++
 doc/sphinx/proof-engine/tactics.rst                         | 13 +++++++++++++
 plugins/ltac/g_tactic.mlg                                   | 10 ++++++++++
 test-suite/success/pose.v                                   |  9 +++++++++
 4 files changed, 38 insertions(+)
 create mode 100644 doc/changelog/04-tactics/11522-master+pose-proof-wo-as-syntax.rst
 create mode 100644 test-suite/success/pose.v

diff --git a/doc/changelog/04-tactics/11522-master+pose-proof-wo-as-syntax.rst b/doc/changelog/04-tactics/11522-master+pose-proof-wo-as-syntax.rst
new file mode 100644
index 0000000000..579ccf839f
--- /dev/null
+++ b/doc/changelog/04-tactics/11522-master+pose-proof-wo-as-syntax.rst
@@ -0,0 +1,6 @@
+- **Added:**
+  Syntax :tacn:`pose proof (@ident:=@term)` as an
+  alternative to `pose proof @term as @ident`, following the model of
+  :tacn:`pose (@ident:=@term)`
+  (`#11522 <https://github.com/coq/coq/pull/11522>`_,
+  by Hugo Herbelin).
diff --git a/doc/sphinx/proof-engine/tactics.rst b/doc/sphinx/proof-engine/tactics.rst
index 6a0ce20c79..206342fef1 100644
--- a/doc/sphinx/proof-engine/tactics.rst
+++ b/doc/sphinx/proof-engine/tactics.rst
@@ -1452,6 +1452,19 @@ Controlling the proof flow
    While :tacn:`pose proof` expects that no existential variables are generated by
    the tactic, :tacn:`epose proof` removes this constraint.
 
+.. tacv:: pose proof (@ident := @term)
+
+   This is an alternative syntax for :n:`assert (@ident := @term)` and
+   :n:`pose proof @term as @ident`, following the model of :n:`pose
+   (@ident := @term)` but dropping the value of :token:`ident`.
+
+.. tacv:: epose proof (@ident := @term)
+
+   This is an alternative syntax for :n:`eassert (@ident := @term)`
+   and :n:`epose proof @term as @ident`, following the model of
+   :n:`epose (@ident := @term)` but dropping the value of
+   :token:`ident`.
+
 .. tacv:: enough (@ident : @type)
    :name: enough
 
diff --git a/plugins/ltac/g_tactic.mlg b/plugins/ltac/g_tactic.mlg
index f0d6258cd1..fe762b4a1f 100644
--- a/plugins/ltac/g_tactic.mlg
+++ b/plugins/ltac/g_tactic.mlg
@@ -611,6 +611,16 @@ GRAMMAR EXTEND Gram
           { TacAtom (CAst.make ~loc @@ TacAssert (false,true,Some tac,ipat,c)) }
       | IDENT "eassert"; c = constr; ipat = as_ipat; tac = by_tactic ->
           { TacAtom (CAst.make ~loc @@ TacAssert (true,true,Some tac,ipat,c)) }
+
+      (* Alternative syntax for "pose proof c as id by tac" *)
+      | IDENT "pose"; IDENT "proof"; test_lpar_id_coloneq; "("; lid = identref; ":=";
+          c = lconstr; ")" ->
+          { let { CAst.loc = loc; v = id } = lid in
+          TacAtom (CAst.make ?loc @@ TacAssert (false,true,None,Some (CAst.make ?loc @@ IntroNaming (IntroIdentifier id)),c)) }
+      | IDENT "epose"; IDENT "proof"; test_lpar_id_coloneq; "("; lid = identref; ":=";
+          c = lconstr; ")" ->
+          { let { CAst.loc = loc; v = id } = lid in
+          TacAtom (CAst.make ?loc @@ TacAssert (true,true,None,Some (CAst.make ?loc @@ IntroNaming (IntroIdentifier id)),c)) }
       | IDENT "pose"; IDENT "proof"; c = lconstr; ipat = as_ipat ->
           { TacAtom (CAst.make ~loc @@ TacAssert (false,true,None,ipat,c)) }
       | IDENT "epose"; IDENT "proof"; c = lconstr; ipat = as_ipat ->
diff --git a/test-suite/success/pose.v b/test-suite/success/pose.v
new file mode 100644
index 0000000000..17007915fe
--- /dev/null
+++ b/test-suite/success/pose.v
@@ -0,0 +1,9 @@
+(* Test syntax *)
+
+Goal 0=0.
+pose proof (a := I).
+Fail clearbody a.
+epose proof (b := fun _ => eq_refl).
+Fail clearbody b.
+exact (b a).
+Qed.
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