feat(frontends/lean): add 'begin+' and 'by+' that enter tactic mode with the whole context visible

src/emacs/lean-syntax.el

@@ -9,7 +9,7 @@
 
 (defconst lean-keywords
   '("import" "prelude" "tactic_hint" "protected" "private" "opaque" "definition" "renaming"
-    "hiding" "exposing" "parameter" "parameters" "begin" "proof" "qed" "conjecture" "constant" "constants"
+    "hiding" "exposing" "parameter" "parameters" "begin" "begin+" "proof" "qed" "conjecture" "constant" "constants"
     "hypothesis" "lemma" "corollary" "variable" "variables" "premise" "premises"
     "print" "theorem" "example" "abbreviation"
     "open" "as" "export" "axiom" "axioms" "inductive" "with" "structure" "record" "universe" "universes"
@@ -98,7 +98,7 @@
 
 (defconst lean-font-lock-defaults
   `((;; Keywords
-     (,(rx word-start (or "calc" "have" "obtains" "show" "by" "in" "at" "let" "forall" "fun"
+     (,(rx word-start (or "calc" "have" "obtains" "show" "by" "by+" "in" "at" "let" "forall" "fun"
                             "exists" "if" "dif" "then" "else" "assume" "assert" "take" "obtain" "from") word-end)
       . font-lock-keyword-face)
      ;; String

src/frontends/lean/builtin_exprs.cpp

@@ -130,7 +130,13 @@ static expr parse_by(parser & p, unsigned, expr const *, pos_info const & pos) {
     return p.mk_by(t, pos);
 }
 
-static expr parse_begin_end_core(parser & p, pos_info const & pos, name const & end_token, bool nested = false) {
+static expr parse_by_plus(parser & p, unsigned, expr const *, pos_info const & pos) {
+    p.next();
+    expr t = p.parse_tactic();
+    return p.mk_by_plus(t, pos);
+}
+
+static expr parse_begin_end_core(parser & p, pos_info const & pos, name const & end_token, bool plus, bool nested = false) {
     if (!p.has_tactic_decls())
         throw parser_error("invalid 'begin-end' expression, tactic module has not been imported", pos);
     p.next();
@@ -159,10 +165,10 @@ static expr parse_begin_end_core(parser & p, pos_info const & pos, name const &
             }
             if (p.curr_is_token(get_begin_tk())) {
                 auto pos = p.pos();
-                tacs.push_back(parse_begin_end_core(p, pos, get_end_tk(), true));
+                tacs.push_back(parse_begin_end_core(p, pos, get_end_tk(), plus, true));
             } else if (p.curr_is_token(get_lcurly_tk())) {
                 auto pos = p.pos();
-                tacs.push_back(parse_begin_end_core(p, pos, get_rcurly_tk(), true));
+                tacs.push_back(parse_begin_end_core(p, pos, get_rcurly_tk(), plus, true));
             } else if (p.curr_is_token(end_token)) {
                 break;
             } else if (p.curr_is_token(get_assert_tk())) {
@@ -211,7 +217,7 @@ static expr parse_begin_end_core(parser & p, pos_info const & pos, name const &
                         add_tac(t, pos);
                     } else if (p.curr_is_token(get_begin_tk())) {
                         auto pos = p.pos();
-                        tacs.push_back(parse_begin_end_core(p, pos, get_end_tk(), true));
+                        tacs.push_back(parse_begin_end_core(p, pos, get_end_tk(), plus, true));
                     } else if (p.curr_is_token(get_by_tk())) {
                         // parse: 'by' tactic
                         auto pos = p.pos();
@@ -265,12 +271,18 @@ static expr parse_begin_end_core(parser & p, pos_info const & pos, name const &
     r = p.save_pos(mk_begin_end_annotation(r), end_pos);
     if (nested)
         return r;
+    else if (plus)
+        return p.mk_by_plus(r, end_pos);
     else
         return p.mk_by(r, end_pos);
 }
 
 static expr parse_begin_end(parser & p, unsigned, expr const *, pos_info const & pos) {
-    return parse_begin_end_core(p, pos, get_end_tk());
+    return parse_begin_end_core(p, pos, get_end_tk(), false);
+}
+
+static expr parse_begin_end_plus(parser & p, unsigned, expr const *, pos_info const & pos) {
+    return parse_begin_end_core(p, pos, get_end_tk(), true);
 }
 
 static expr parse_proof_qed_core(parser & p, pos_info const & pos) {
@@ -328,7 +340,10 @@ static expr parse_proof(parser & p, expr const & prop) {
         return parse_proof_qed_core(p, pos);
     } else if (p.curr_is_token(get_begin_tk())) {
         auto pos = p.pos();
-        return parse_begin_end_core(p, pos, get_end_tk());
+        return parse_begin_end_core(p, pos, get_end_tk(), false);
+    } else if (p.curr_is_token(get_begin_plus_tk())) {
+        auto pos = p.pos();
+        return parse_begin_end_core(p, pos, get_end_tk(), true);
     } else if (p.curr_is_token(get_by_tk())) {
         // parse: 'by' tactic
         auto pos = p.pos();
@@ -576,6 +591,7 @@ parse_table init_nud_table() {
     parse_table r;
     r = r.add({transition("_", mk_ext_action(parse_placeholder))}, x0);
     r = r.add({transition("by", mk_ext_action_core(parse_by))}, x0);
+    r = r.add({transition("by+", mk_ext_action_core(parse_by_plus))}, x0);
     r = r.add({transition("have", mk_ext_action(parse_have))}, x0);
     r = r.add({transition("assert", mk_ext_action(parse_assert))}, x0);
     r = r.add({transition("show", mk_ext_action(parse_show))}, x0);
@@ -593,6 +609,7 @@ parse_table init_nud_table() {
     r = r.add({transition("@", mk_ext_action(parse_explicit_expr))}, x0);
     r = r.add({transition("!", mk_ext_action(parse_consume_args_expr))}, x0);
     r = r.add({transition("begin", mk_ext_action_core(parse_begin_end))}, x0);
+    r = r.add({transition("begin+", mk_ext_action_core(parse_begin_end_plus))}, x0);
     r = r.add({transition("proof", mk_ext_action(parse_proof_qed))}, x0);
     r = r.add({transition("using", mk_ext_action(parse_using))}, x0);
     r = r.add({transition("sorry", mk_ext_action(parse_sorry))}, x0);

src/frontends/lean/token_table.cpp

@@ -89,7 +89,7 @@ static char const * g_decreasing_unicode = "↓";
 void init_token_table(token_table & t) {
     pair<char const *, unsigned> builtin[] =
         {{"fun", 0}, {"Pi", 0}, {"let", 0}, {"in", 0}, {"at", 0}, {"have", 0}, {"assert", 0}, {"show", 0}, {"obtain", 0},
-         {"if", 0}, {"then", 0}, {"else", 0}, {"by", 0}, {"hiding", 0}, {"replacing", 0}, {"renaming", 0},
+         {"if", 0}, {"then", 0}, {"else", 0}, {"by", 0}, {"by+", 0}, {"hiding", 0}, {"replacing", 0}, {"renaming", 0},
          {"from", 0}, {"(", g_max_prec}, {")", 0}, {"{", g_max_prec}, {"}", 0}, {"_", g_max_prec},
          {"[", g_max_prec}, {"]", 0}, {"⦃", g_max_prec}, {"⦄", 0}, {".{", 0}, {"Type", g_max_prec},
          {"{|", g_max_prec}, {"|}", 0}, {"⊢", 0}, {"⟨", g_max_prec}, {"⟩", 0}, {"^", 0}, {"↑", 0}, {"▸", 0},
@@ -97,7 +97,7 @@ void init_token_table(token_table & t) {
          {".", 0}, {":", 0}, {"::", 0}, {"calc", 0}, {"rewrite", 0}, {"esimp", 0}, {"fold", 0}, {"unfold", 0},
          {"generalize", 0}, {"as", 0},
          {":=", 0}, {"--", 0}, {"#", 0},
-         {"(*", 0}, {"/-", 0}, {"begin", g_max_prec}, {"proof", g_max_prec}, {"qed", 0}, {"@", g_max_prec},
+         {"(*", 0}, {"/-", 0}, {"begin", g_max_prec}, {"begin+", g_max_prec}, {"proof", g_max_prec}, {"qed", 0}, {"@", g_max_prec},
          {"sorry", g_max_prec}, {"+", g_plus_prec}, {g_cup, g_cup_prec}, {"->", g_arrow_prec},
          {"?(", g_max_prec}, {"⌞", g_max_prec}, {"⌟", 0}, {"match", 0},
          {"<d", g_decreasing_prec}, {"renaming", 0}, {"extends", 0}, {nullptr, 0}};

src/frontends/lean/tokens.cpp

@@ -89,6 +89,7 @@ static name * g_rewrite      = nullptr;
 static name * g_proof        = nullptr;
 static name * g_qed          = nullptr;
 static name * g_begin        = nullptr;
+static name * g_beginp       = nullptr;
 static name * g_end          = nullptr;
 static name * g_private      = nullptr;
 static name * g_definition   = nullptr;
@@ -223,6 +224,7 @@ void initialize_tokens() {
     g_proof        = new name("proof");
     g_qed          = new name("qed");
     g_begin        = new name("begin");
+    g_beginp       = new name("beginp");
     g_end          = new name("end");
     g_private      = new name("private");
     g_definition   = new name("definition");
@@ -338,6 +340,7 @@ void finalize_tokens() {
     delete g_proof;
     delete g_qed;
     delete g_begin;
+    delete g_beginp;
     delete g_end;
     delete g_raw;
     delete g_true;
@@ -494,6 +497,7 @@ name const & get_rewrite_tk() { return *g_rewrite; }
 name const & get_proof_tk() { return *g_proof; }
 name const & get_qed_tk() { return *g_qed; }
 name const & get_begin_tk() { return *g_begin; }
+name const & get_begin_plus_tk() { return *g_beginp; }
 name const & get_end_tk() { return *g_end; }
 name const & get_private_tk() { return *g_private; }
 name const & get_definition_tk() { return *g_definition; }

src/frontends/lean/tokens.h

@@ -90,6 +90,7 @@ name const & get_by_tk();
 name const & get_rewrite_tk();
 name const & get_proof_tk();
 name const & get_begin_tk();
+name const & get_begin_plus_tk();
 name const & get_qed_tk();
 name const & get_end_tk();
 name const & get_private_tk();

tests/lean/run/begin_end_plus.lean

@@ -0,0 +1,13 @@
+example (a b c : Prop) : a → b → c → a ∧ c ∧ b :=
+assume Ha Hb Hc,
+have aux : c ∧ b, from and.intro Hc Hb,
+begin+  -- the whole context is visible
+  split,
+  state,
+  repeat assumption
+end
+
+example (a b c : Prop) : a → b → c → a ∧ c ∧ b :=
+assume Ha Hb Hc,
+have aux : c ∧ b, from and.intro Hc Hb,
+by+ split; repeat assumption