feat(frontends/lean): add let-expr pretty printer, reduce default indentation to 2

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>

src/frontends/lean/pp.cpp

@@ -10,6 +10,7 @@ Author: Leonardo de Moura
 #include "library/aliases.h"
 #include "library/scoped_ext.h"
 #include "library/coercion.h"
+#include "library/expr_pair.h"
 #include "frontends/lean/pp.h"
 #include "frontends/lean/pp_options.h"
 #include "frontends/lean/token_table.h"
@@ -25,6 +26,9 @@ static format g_pi_n_fmt      = highlight_keyword(format("Π"));
 static format g_pi_fmt        = highlight_keyword(format("Pi"));
 static format g_arrow_n_fmt   = highlight_keyword(format("\u2192"));
 static format g_arrow_fmt     = highlight_keyword(format("->"));
+static format g_let_fmt       = highlight_keyword(format("let"));
+static format g_in_fmt        = highlight_keyword(format("in"));
+static format g_assign_fmt    = highlight_keyword(format(":="));
 
 name pretty_fn::mk_metavar_name(name const & m) {
     if (auto it = m_purify_meta_table.find(m))
@@ -272,14 +276,51 @@ auto pretty_fn::pp_pi(expr const & e) -> result {
     }
 }
 
+auto pretty_fn::pp_let(expr e) -> result {
+    buffer<expr_pair> decls;
+    while (true) {
+        if (!is_let_macro(e))
+            break;
+        e = let_macro_arg(e);
+        if (!is_app(e) || !is_lambda(app_fn(e)))
+            break;
+        expr v = app_arg(e);
+        auto p = binding_body_fresh(app_fn(e), true);
+        decls.emplace_back(p.second, v);
+        e = p.first;
+    }
+    if (decls.empty())
+        return pp(e);
+    format r    = g_let_fmt;
+    unsigned sz = decls.size();
+    for (unsigned i = 0; i < sz; i++) {
+        auto const & d = decls[i];
+        format beg     = i == 0 ? space() : line();
+        format sep     = i < sz - 1 ? comma() : format();
+        name const & n = local_pp_name(d.first);
+        format t       = pp_child(mlocal_type(d.first), 0).first;
+        format v       = pp_child(d.second, 0).first;
+        r += nest(3 + 1, compose(beg, group(format{format(n), space(),
+                            colon(), nest(n.size() + 1 + 1 + 1, compose(space(), t)), space(), g_assign_fmt,
+                            nest(m_indent, format{line(), v, sep})})));
+    }
+    format b = pp_child(e, 0).first;
+    r += format{line(), g_in_fmt, space(), nest(2 + 1, b)};
+    return mk_result(r, 0);
+}
+
 auto pretty_fn::pp_macro(expr const & e) -> result {
-    // TODO(Leo): handle let, have macro annotations
+    if (is_let_macro(e)) {
+        return pp_let(e);
+    } else {
+        // TODO(Leo): have macro annotations
         // fix macro<->pp interface
         format r = compose(format("["), format(macro_def(e).get_name()));
         for (unsigned i = 0; i < macro_num_args(e); i++)
             r += nest(m_indent, compose(line(), pp_child(macro_arg(e, i), max_bp()).first));
         r += format("]");
         return mk_result(group(r));
+    }
 }
 
 auto pretty_fn::pp(expr const & e) -> result {

src/frontends/lean/pp.h

@@ -62,6 +62,7 @@ private:
     result pp_app(expr const & e);
     result pp_lambda(expr const & e);
     result pp_pi(expr const & e);
+    result pp_let(expr e);
     result pp_macro(expr const & e);
 
 public:

src/util/sexpr/format.cpp

@@ -20,7 +20,7 @@
 #include "util/sexpr/options.h"
 
 #ifndef LEAN_DEFAULT_PP_INDENTATION
-#define LEAN_DEFAULT_PP_INDENTATION 4
+#define LEAN_DEFAULT_PP_INDENTATION 2
 #endif
 
 #ifndef LEAN_DEFAULT_PP_UNICODE

tests/lean/let1.lean.expected.out

@@ -1,36 +1,29 @@
-[let
+let and_intro : ∀ (p q : Bool),
-    ((λ (and_intro : ∀ (p q : Bool), p → q → (λ (p q : Bool), ∀ (c : Bool), (p → q → c) → c) p q),
+                  p → q → (λ (p q : Bool), ∀ (c : Bool), (p → q → c) → c) p q :=
-          [let
+      λ (p q : Bool) (H1 : p) (H2 : q) (c : Bool) (H : p → q → c),
-              ((λ
+        H H1 H2,
-                (and_elim_left : ∀ (p q : Bool), (λ (p q : Bool), ∀ (c : Bool), (p → q → c) → c) p q → p),
+    and_elim_left : ∀ (p q : Bool),
-                    [let
+                      (λ (p q : Bool), ∀ (c : Bool), (p → q → c) → c) p q → p :=
-                        ((λ
+      λ (p q : Bool) (H : (λ (p q : Bool), ∀ (c : Bool), (p → q → c) → c) p q),
-                          (and_elim_right :
+        H p (λ (H1 : p) (H2 : q), H1),
-                              ∀ (p q : Bool),
+    and_elim_right : ∀ (p q : Bool),
-                                  (λ (p q : Bool), ∀ (c : Bool), (p → q → c) → c) p q → q),
+                       (λ (p q : Bool), ∀ (c : Bool), (p → q → c) → c) p q → q :=
-                              and_intro)
+      λ (p q : Bool) (H : (λ (p q : Bool), ∀ (c : Bool), (p → q → c) → c) p q),
-                             (λ (p q : Bool) (H : (λ (p q : Bool), ∀ (c : Bool), (p → q → c) → c) p q),
+        H q (λ (H1 : p) (H2 : q), H2)
-                                  H q (λ (H1 : p) (H2 : q), H2)))])
+in and_intro :
-                   (λ (p q : Bool) (H : (λ (p q : Bool), ∀ (c : Bool), (p → q → c) → c) p q),
-                        H p (λ (H1 : p) (H2 : q), H1)))])
-         (λ (p q : Bool) (H1 : p) (H2 : q) (c : Bool) (H : p → q → c), H H1 H2))] :
   ∀ (p q : Bool),
     p → q → (λ (p q : Bool), ∀ (c : Bool), (p → q → c) → c) p q
 let1.lean:17:20: error: type mismatch at application
   (λ (and_intro : ∀ (p q : Bool), p → q → (λ (p q : Bool), ∀ (c : Bool), (p → q → c) → c) q p),
-         [let
+     let and_elim_left : ∀ (p q : Bool),
-             ((λ
+                           (λ (p q : Bool), ∀ (c : Bool), (p → q → c) → c) p q → p :=
-               (and_elim_left : ∀ (p q : Bool), (λ (p q : Bool), ∀ (c : Bool), (p → q → c) → c) p q → p),
+           λ (p q : Bool) (H : (λ (p q : Bool), ∀ (c : Bool), (p → q → c) → c) p q),
-                   [let
+             H p (λ (H1 : p) (H2 : q), H1),
-                       ((λ
+         and_elim_right : ∀ (p q : Bool),
-                         (and_elim_right :
+                            (λ (p q : Bool), ∀ (c : Bool), (p → q → c) → c) p q → q :=
-                             ∀ (p q : Bool),
+           λ (p q : Bool) (H : (λ (p q : Bool), ∀ (c : Bool), (p → q → c) → c) p q),
-                                 (λ (p q : Bool), ∀ (c : Bool), (p → q → c) → c) p q → q),
+             H q (λ (H1 : p) (H2 : q), H2)
-                             and_intro)
+     in and_intro)
-                            (λ (p q : Bool) (H : (λ (p q : Bool), ∀ (c : Bool), (p → q → c) → c) p q),
-                                 H q (λ (H1 : p) (H2 : q), H2)))])
-                  (λ (p q : Bool) (H : (λ (p q : Bool), ∀ (c : Bool), (p → q → c) → c) p q),
-                       H p (λ (H1 : p) (H2 : q), H1)))])
     (λ (p q : Bool) (H1 : p) (H2 : q) (c : Bool) (H : p → q → c), H H1 H2)
 expected type:
   ∀ (p q : Bool),

tests/lean/run/t6.lean

@@ -3,7 +3,7 @@ precedence `++` : 100
 variable N : Type.{1}
 variable f : N → N → N
 variable a : N
-print raw
+check
    let g x y         := f x y,
        infix +       := g,
        b : N         := a+a,