Merge eval-ast and macro expansion into EVAL, add DEBUG-EVAL

See issue kanaka#587.
 * Merge eval-ast and eval into a single conditional.
 * Expand macros during the apply phase, removing lots of duplicate
   tests, and increasing the overall consistency by allowing the macro
   to be computed instead of referenced by name (`((defmacro! cond
   (...)))` is currently illegal for example).
 * Print "EVAL: $ast" at the top of EVAL if DEBUG-EVAL exists in the
   MAL environment.
 * Remove macroexpand and quasiquoteexpand special forms.
 * Use pattern-matching style in process/step*.txt.

Unrelated fixes:
c: also fixe defmacro so that it does not mutate functions.
ocaml: also remove metadata from symbols.
ruby.2: step9 was failing with REGRESS=1, the fix is now backported.

Unresolved issues:
c.2: unable to reproduce with gcc 11.12.0.
elm: the directory is unchanged.
groovy: sometimes fail, but not on each rebuild.
nasm: fails some new soft tests, but the issue is unreproducible when
  running the interpreter manually.
objpascal: unreproducible with fpc 3.2.2.
ocaml: unreproducible with 4.11.1.
perl6: unreproducible with rakudo 2021.09.

impls/ada.2/envs.adb

@@ -53,6 +53,25 @@ package body Envs is
       return HM.Element (Position);
    end Get;
 
+   function Get_Or_Nil (Env : Instance;
+                        Key : Types.String_Ptr) return Types.T is
+      Position : HM.Cursor := Env.Data.Find (Key);
+      Ref      : Link;
+   begin
+      if not HM.Has_Element (Position) then
+         Ref := Env.Outer;
+         loop
+            if Ref = null then
+               return Types.Nil;
+            end if;
+            Position := Ref.all.Data.Find (Key);
+            exit when HM.Has_Element (Position);
+            Ref := Ref.all.Outer;
+         end loop;
+      end if;
+      return HM.Element (Position);
+   end Get_Or_Nil;
+
    procedure Keep_References (Object : in out Instance) is
    begin
       for Position in Object.Data.Iterate loop

impls/ada.2/envs.ads

@@ -27,6 +27,9 @@ package Envs is
    function Get (Env : in Instance;
                  Key : in Types.String_Ptr) return Types.T;
 
+   function Get_Or_Nil (Env : Instance;
+                        Key : Types.String_Ptr) return Types.T;
+
    procedure Set (Env      : in out Instance;
                   Key      : in     Types.T;
                   New_Item : in     Types.T) with Inline;

impls/ada.2/step2_eval.adb

@@ -1,4 +1,3 @@
-with Ada.Environment_Variables;
 with Ada.Containers.Indefinite_Hashed_Maps;
 with Ada.Strings.Hash;
 with Ada.Text_IO.Unbounded_IO;
@@ -14,7 +13,7 @@ with Types.Strings;
 
 procedure Step2_Eval is
 
-   Dbgeval : constant Boolean := Ada.Environment_Variables.Exists ("dbgeval");
+   Dbgeval : constant Boolean := False;
 
    use type Types.T;
    use all type Types.Kind_Type;
@@ -53,11 +52,9 @@ procedure Step2_Eval is
       First          : Types.T;
    begin
       if Dbgeval then
-         Ada.Text_IO.New_Line;
          Ada.Text_IO.Put ("EVAL: ");
          Print (Ast);
       end if;
-
       case Ast.Kind is
       when Kind_Nil | Kind_Atom | Kind_Boolean | Kind_Number | Types.Kind_Key
         | Kind_Macro | Types.Kind_Function =>

impls/ada.2/step3_env.adb

@@ -1,4 +1,3 @@
-with Ada.Environment_Variables;
 with Ada.Text_IO.Unbounded_IO;
 
 with Envs;
@@ -13,7 +12,7 @@ with Types.Strings;
 
 procedure Step3_Env is
 
-   Dbgeval : constant Boolean := Ada.Environment_Variables.Exists ("dbgeval");
+   Dbgeval : constant Types.String_Ptr := Types.Strings.Alloc ("DEBUG-EVAL");
 
    use type Types.T;
    use all type Types.Kind_Type;
@@ -45,8 +44,8 @@ procedure Step3_Env is
    is
       First          : Types.T;
    begin
-      if Dbgeval then
-         Ada.Text_IO.New_Line;
+      <<Restart>>
+      if Types.To_Boolean (Env.all.Get_Or_Nil (Dbgeval)) then
          Ada.Text_IO.Put ("EVAL: ");
          Print (Ast);
          Envs.Dump_Stack (Env.all);
@@ -209,6 +208,7 @@ begin
       --  Collect garbage.
       Err.Data := Types.Nil;
       Repl.all.Keep;
+      Dbgeval.Keep;
       Garbage_Collected.Clean;
    end loop;
    Ada.Text_IO.New_Line;

impls/ada.2/step4_if_fn_do.adb

@@ -1,4 +1,3 @@
-with Ada.Environment_Variables;
 with Ada.Text_IO.Unbounded_IO;
 
 with Core;
@@ -15,7 +14,7 @@ with Types.Strings;
 
 procedure Step4_If_Fn_Do is
 
-   Dbgeval : constant Boolean := Ada.Environment_Variables.Exists ("dbgeval");
+   Dbgeval : constant Types.String_Ptr := Types.Strings.Alloc ("DEBUG-EVAL");
 
    use type Types.T;
    use all type Types.Kind_Type;
@@ -47,8 +46,8 @@ procedure Step4_If_Fn_Do is
    is
       First          : Types.T;
    begin
-      if Dbgeval then
-         Ada.Text_IO.New_Line;
+      <<Restart>>
+      if Types.To_Boolean (Env.all.Get_Or_Nil (Dbgeval)) then
          Ada.Text_IO.Put ("EVAL: ");
          Print (Ast);
          Envs.Dump_Stack (Env.all);
@@ -81,17 +80,13 @@ procedure Step4_If_Fn_Do is
          if First.Str.all = "if" then
             Err.Check (Ast.Sequence.all.Length in 3 .. 4,
                        "expected 2 or 3 parameters");
-            declare
-               Tst : constant Types.T := Eval (Ast.Sequence.all.Data (2), Env);
-            begin
-               if Tst /= Types.Nil and Tst /= (Kind_Boolean, False) then
-                  return Eval (Ast.Sequence.all.Data (3), Env);
-               elsif Ast.Sequence.all.Length = 3 then
-                  return Types.Nil;
-               else
-                  return Eval (Ast.Sequence.all.Data (4), Env);
-               end if;
-            end;
+            if Types.To_Boolean (Eval (Ast.Sequence.all.Data (2), Env)) then
+               return Eval (Ast.Sequence.all.Data (3), Env);
+            elsif Ast.Sequence.all.Length = 3 then
+               return Types.Nil;
+            else
+               return Eval (Ast.Sequence.all.Data (4), Env);
+            end if;
          elsif First.Str.all = "let*" then
             Err.Check (Ast.Sequence.all.Length = 3
                and then Ast.Sequence.all.Data (2).Kind in Types.Kind_Sequence,
@@ -251,6 +246,7 @@ begin
       --  Collect garbage.
       Err.Data := Types.Nil;
       Repl.all.Keep;
+      Dbgeval.Keep;
       Garbage_Collected.Clean;
    end loop;
    Ada.Text_IO.New_Line;

impls/ada.2/step5_tco.adb

@@ -1,4 +1,3 @@
-with Ada.Environment_Variables;
 with Ada.Text_IO.Unbounded_IO;
 
 with Core;
@@ -15,7 +14,7 @@ with Types.Strings;
 
 procedure Step5_Tco is
 
-   Dbgeval : constant Boolean := Ada.Environment_Variables.Exists ("dbgeval");
+   Dbgeval : constant Types.String_Ptr := Types.Strings.Alloc ("DEBUG-EVAL");
 
    use type Types.T;
    use all type Types.Kind_Type;
@@ -56,8 +55,7 @@ procedure Step5_Tco is
       First          : Types.T;
    begin
       <<Restart>>
-      if Dbgeval then
-         Ada.Text_IO.New_Line;
+      if Types.To_Boolean (Env.all.Get_Or_Nil (Dbgeval)) then
          Ada.Text_IO.Put ("EVAL: ");
          Print (Ast);
          Envs.Dump_Stack (Env.all);
@@ -90,19 +88,15 @@ procedure Step5_Tco is
          if First.Str.all = "if" then
             Err.Check (Ast.Sequence.all.Length in 3 .. 4,
                        "expected 2 or 3 parameters");
-            declare
-               Tst : constant Types.T := Eval (Ast.Sequence.all.Data (2), Env);
-            begin
-               if Tst /= Types.Nil and Tst /= (Kind_Boolean, False) then
-                  Ast := Ast.Sequence.all.Data (3);
-                  goto Restart;
-               elsif Ast.Sequence.all.Length = 3 then
-                  return Types.Nil;
-               else
-                  Ast := Ast.Sequence.all.Data (4);
-                  goto Restart;
-               end if;
-            end;
+            if Types.To_Boolean (Eval (Ast.Sequence.all.Data (2), Env)) then
+               Ast := Ast.Sequence.all.Data (3);
+               goto Restart;
+            elsif Ast.Sequence.all.Length = 3 then
+               return Types.Nil;
+            else
+               Ast := Ast.Sequence.all.Data (4);
+               goto Restart;
+            end if;
          elsif First.Str.all = "let*" then
             Err.Check (Ast.Sequence.all.Length = 3
                and then Ast.Sequence.all.Data (2).Kind in Types.Kind_Sequence,
@@ -284,6 +278,7 @@ begin
       --  Collect garbage.
       Err.Data := Types.Nil;
       Repl.all.Keep;
+      Dbgeval.Keep;
       Garbage_Collected.Clean;
    end loop;
    Ada.Text_IO.New_Line;

impls/ada.2/step6_file.adb

@@ -1,5 +1,4 @@
 with Ada.Command_Line;
-with Ada.Environment_Variables;
 with Ada.Text_IO.Unbounded_IO;
 
 with Core;
@@ -16,7 +15,7 @@ with Types.Strings;
 
 procedure Step6_File is
 
-   Dbgeval : constant Boolean := Ada.Environment_Variables.Exists ("dbgeval");
+   Dbgeval : constant Types.String_Ptr := Types.Strings.Alloc ("DEBUG-EVAL");
 
    use type Types.T;
    use all type Types.Kind_Type;
@@ -60,8 +59,7 @@ procedure Step6_File is
       First          : Types.T;
    begin
       <<Restart>>
-      if Dbgeval then
-         Ada.Text_IO.New_Line;
+      if Types.To_Boolean (Env.all.Get_Or_Nil (Dbgeval)) then
          Ada.Text_IO.Put ("EVAL: ");
          Print (Ast);
          Envs.Dump_Stack (Env.all);
@@ -94,19 +92,15 @@ procedure Step6_File is
          if First.Str.all = "if" then
             Err.Check (Ast.Sequence.all.Length in 3 .. 4,
                        "expected 2 or 3 parameters");
-            declare
-               Tst : constant Types.T := Eval (Ast.Sequence.all.Data (2), Env);
-            begin
-               if Tst /= Types.Nil and Tst /= (Kind_Boolean, False) then
-                  Ast := Ast.Sequence.all.Data (3);
-                  goto Restart;
-               elsif Ast.Sequence.all.Length = 3 then
-                  return Types.Nil;
-               else
-                  Ast := Ast.Sequence.all.Data (4);
-                  goto Restart;
-               end if;
-            end;
+            if Types.To_Boolean (Eval (Ast.Sequence.all.Data (2), Env)) then
+               Ast := Ast.Sequence.all.Data (3);
+               goto Restart;
+            elsif Ast.Sequence.all.Length = 3 then
+               return Types.Nil;
+            else
+               Ast := Ast.Sequence.all.Data (4);
+               goto Restart;
+            end if;
          elsif First.Str.all = "let*" then
             Err.Check (Ast.Sequence.all.Length = 3
                and then Ast.Sequence.all.Data (2).Kind in Types.Kind_Sequence,
@@ -310,6 +304,7 @@ begin
          --  Collect garbage.
          Err.Data := Types.Nil;
          Repl.all.Keep;
+         Dbgeval.Keep;
          Garbage_Collected.Clean;
       end loop;
       Ada.Text_IO.New_Line;

impls/ada.2/step7_quote.adb

@@ -1,5 +1,4 @@
 with Ada.Command_Line;
-with Ada.Environment_Variables;
 with Ada.Text_IO.Unbounded_IO;
 
 with Core;
@@ -16,7 +15,7 @@ with Types.Strings;
 
 procedure Step7_Quote is
 
-   Dbgeval : constant Boolean := Ada.Environment_Variables.Exists ("dbgeval");
+   Dbgeval : constant Types.String_Ptr := Types.Strings.Alloc ("DEBUG-EVAL");
 
    use type Types.T;
    use all type Types.Kind_Type;
@@ -62,8 +61,7 @@ procedure Step7_Quote is
       First          : Types.T;
    begin
       <<Restart>>
-      if Dbgeval then
-         Ada.Text_IO.New_Line;
+      if Types.To_Boolean (Env.all.Get_Or_Nil (Dbgeval)) then
          Ada.Text_IO.Put ("EVAL: ");
          Print (Ast);
          Envs.Dump_Stack (Env.all);
@@ -96,19 +94,15 @@ procedure Step7_Quote is
          if First.Str.all = "if" then
             Err.Check (Ast.Sequence.all.Length in 3 .. 4,
                        "expected 2 or 3 parameters");
-            declare
-               Tst : constant Types.T := Eval (Ast.Sequence.all.Data (2), Env);
-            begin
-               if Tst /= Types.Nil and Tst /= (Kind_Boolean, False) then
-                  Ast := Ast.Sequence.all.Data (3);
-                  goto Restart;
-               elsif Ast.Sequence.all.Length = 3 then
-                  return Types.Nil;
-               else
-                  Ast := Ast.Sequence.all.Data (4);
-                  goto Restart;
-               end if;
-            end;
+            if Types.To_Boolean (Eval (Ast.Sequence.all.Data (2), Env)) then
+               Ast := Ast.Sequence.all.Data (3);
+               goto Restart;
+            elsif Ast.Sequence.all.Length = 3 then
+               return Types.Nil;
+            else
+               Ast := Ast.Sequence.all.Data (4);
+               goto Restart;
+            end if;
          elsif First.Str.all = "let*" then
             Err.Check (Ast.Sequence.all.Length = 3
                and then Ast.Sequence.all.Data (2).Kind in Types.Kind_Sequence,
@@ -167,9 +161,6 @@ procedure Step7_Quote is
                   Ast    => Ast.Sequence.all.Data (3),
                   Env    => Env));
             end;
-         elsif First.Str.all = "quasiquoteexpand" then
-            Err.Check (Ast.Sequence.all.Length = 2, "expected 1 parameter");
-            return Quasiquote (Ast.Sequence.all.Data (2));
          elsif First.Str.all = "quasiquote" then
             Err.Check (Ast.Sequence.all.Length = 2, "expected 1 parameter");
             Ast := Quasiquote (Ast.Sequence.all.Data (2));
@@ -379,6 +370,7 @@ begin
          --  Collect garbage.
          Err.Data := Types.Nil;
          Repl.all.Keep;
+         Dbgeval.Keep;
          Garbage_Collected.Clean;
       end loop;
       Ada.Text_IO.New_Line;