Explicitly thunk tactic argument of `iPoseProofCoreLem`.

This avoids weird Ltac behaviors like those in !272.

Also, change `before_tc` keyword into `as` to be consistent with other tactics.

tests/proofmode.ref

@@ -554,17 +554,16 @@ Tactic failure: iStartProof: not a BI assertion.
 The command has indeed failed with message:
 In nested Ltac calls to "iPoseProof (open_constr) as (constr)",
 "iPoseProofCore (open_constr) as (constr) (tactic3)",
-"iPoseProofCoreLem (constr) as (constr) before_tc (tactic3)" and
+"iPoseProofCoreLem (constr) as (tactic3)" and
 "<iris.proofmode.ltac_tactics.iIntoEmpValid>", last call failed.
 Tactic failure: iPoseProof: not a BI assertion.
 The command has indeed failed with message:
 In nested Ltac calls to "iPoseProof (open_constr) as (constr)",
 "iPoseProofCore (open_constr) as (constr) (tactic3)",
-"iPoseProofCoreLem (constr) as (constr) before_tc (tactic3)", 
-"tac" (bound to spec_tac ltac:(()); [ .. | tac Htmp ]), 
-"tac" (bound to spec_tac ltac:(()); [ .. | tac Htmp ]), 
-"tac" (bound to fun H => iDestructHyp H as pat),
-"iDestructHyp (constr) as (constr)",
+"iPoseProofCoreLem (constr) as (tactic3)", "tac" (bound to
+fun Htmp => spec_tac Htmp; [ .. | tac Htmp ]), "tac" (bound to
+fun Htmp => spec_tac Htmp; [ .. | tac Htmp ]), "tac" (bound to
+fun H => iDestructHyp H as pat), "iDestructHyp (constr) as (constr)",
 "<iris.proofmode.ltac_tactics.iDestructHypFindPat>",
 "<iris.proofmode.ltac_tactics.iDestructHypGo>" and
 "iRename (constr) into (constr)", last call failed.
@@ -581,11 +580,10 @@ Tactic failure: iPoseProof: "Hx" not found.
 The command has indeed failed with message:
 In nested Ltac calls to "iPoseProof (open_constr) as (constr)",
 "iPoseProofCore (open_constr) as (constr) (tactic3)",
-"iPoseProofCoreLem (constr) as (constr) before_tc (tactic3)", 
-"tac" (bound to spec_tac ltac:(()); [ .. | tac Htmp ]), 
-"tac" (bound to spec_tac ltac:(()); [ .. | tac Htmp ]), 
-"spec_tac" (bound to
-fun _ =>
+"iPoseProofCoreLem (constr) as (tactic3)", "tac" (bound to
+fun Htmp => spec_tac Htmp; [ .. | tac Htmp ]), "tac" (bound to
+fun Htmp => spec_tac Htmp; [ .. | tac Htmp ]), "spec_tac" (bound to
+fun Htmp =>
   lazymatch lem with
   | {| itrm := _; itrm_vars := ?xs; itrm_hyps := ?pat |} => iSpecializeCore
   {| itrm := Htmp; itrm_vars := xs; itrm_hyps := pat |} as p

theories/proofmode/ltac_tactics.v

@@ -725,8 +725,8 @@ Tactic Notation "iPoseProofCoreHyp" constr(H) "as" constr(Hnew) :=
     | _ => idtac
     end.
 
-Tactic Notation "iPoseProofCoreLem"
-    constr(lem) "as" constr(Hnew) "before_tc" tactic3(tac) :=
+Tactic Notation "iPoseProofCoreLem" constr(lem) "as" tactic3(tac) :=
+  let Hnew := iFresh in
   eapply tac_pose_proof with Hnew _; (* (j:=H) *)
     [iIntoEmpValid lem
     |pm_reduce;
@@ -734,7 +734,7 @@ Tactic Notation "iPoseProofCoreLem"
      | |- False =>
        let Hnew := pretty_ident Hnew in
        fail "iPoseProof:" Hnew "not fresh"
-     | _ => tac
+     | _ => tac Hnew
      end];
   (* Solve all remaining TC premises generated by [iIntoEmpValid] *)
   try iSolveTC.
@@ -1002,17 +1002,18 @@ whether the conclusion of the specialized term [lem] is persistent. *)
 Tactic Notation "iPoseProofCore" open_constr(lem)
     "as" constr(p) tactic3(tac) :=
   iStartProof;
-  let Htmp := iFresh in
   let t := lazymatch lem with ITrm ?t ?xs ?pat => t | _ => lem end in
   let t := lazymatch type of t with string => constr:(INamed t) | _ => t end in
-  let spec_tac _ :=
+  let spec_tac Htmp :=
     lazymatch lem with
     | ITrm _ ?xs ?pat => iSpecializeCore (ITrm Htmp xs pat) as p
     | _ => idtac
     end in
   lazymatch type of t with
-  | ident => iPoseProofCoreHyp t as Htmp; spec_tac (); [..|tac Htmp]
-  | _ => iPoseProofCoreLem t as Htmp before_tc (spec_tac (); [..|tac Htmp])
+  | ident =>
+     let Htmp := iFresh in
+     iPoseProofCoreHyp t as Htmp; spec_tac Htmp; [..|tac Htmp]
+  | _ => iPoseProofCoreLem t as (fun Htmp => spec_tac Htmp; [..|tac Htmp])
   end.
 
 (** * The apply tactic *)