Remove 'cond'-expressions from syntax_tools

'cond' expressions were an experimental addition to the Erlang language
that never matured to the point that it could be incorporated to it.

This pull request takes out the (incomplete anyway) handling of 'cond'
expressions from the syntax_tools application, so as to simplify its
code base.

5 files changed, 9 insertions, 102 deletions

diff --git a/lib/syntax_tools/src/epp_dodger.erl b/lib/syntax_tools/src/epp_dodger.erl
index 7e741cc649..da22a91de0 100644
--- a/lib/syntax_tools/src/epp_dodger.erl
+++ b/lib/syntax_tools/src/epp_dodger.erl
@@ -598,8 +598,6 @@ skip_macro_args([{'receive',_}=T | Ts], Es, As) ->
     skip_macro_args(Ts, ['end' | Es], [T | As]);
 skip_macro_args([{'try',_}=T | Ts], Es, As) ->
     skip_macro_args(Ts, ['end' | Es], [T | As]);
-skip_macro_args([{'cond',_}=T | Ts], Es, As) ->
-    skip_macro_args(Ts, ['end' | Es], [T | As]);
 skip_macro_args([{E,_}=T | Ts], [E], As) ->		%final close
     {lists:reverse([T | As]), Ts};
 skip_macro_args([{E,_}=T | Ts], [E | Es], As) ->	%matching close
diff --git a/lib/syntax_tools/src/erl_prettypr.erl b/lib/syntax_tools/src/erl_prettypr.erl
index 6ad9bec2e6..d70dd40a8a 100644
--- a/lib/syntax_tools/src/erl_prettypr.erl
+++ b/lib/syntax_tools/src/erl_prettypr.erl
@@ -53,7 +53,7 @@
 
 -type hook() :: 'none'
               | fun((erl_syntax:syntaxTree(), _, _) -> prettypr:document()).
--type clause_t() :: 'case_expr' | 'cond_expr' | 'fun_expr'
+-type clause_t() :: 'case_expr' | 'fun_expr'
                   | 'if_expr' | 'receive_expr' | 'try_expr'
                   | {'function', prettypr:document()}
                   | 'spec'.
@@ -586,8 +586,6 @@ lay_2(Node, Ctxt) ->
 		    make_fun_clause(N, D1, D2, D3, Ctxt);
 		if_expr ->
 		    make_if_clause(D1, D2, D3, Ctxt);
-		cond_expr ->
-		    make_if_clause(D1, D2, D3, Ctxt);
 		case_expr ->
 		    make_case_clause(D1, D2, D3, Ctxt);
 		receive_expr ->
@@ -627,14 +625,6 @@ lay_2(Node, Ctxt) ->
 	    sep([follow(text("if"), D, Ctxt1#ctxt.sub_indent),
 		 text("end")]);
 
-	cond_expr ->
-	    Ctxt1 = reset_prec(Ctxt),
-	    D = lay_clauses(erl_syntax:cond_expr_clauses(Node),
-			    cond_expr, Ctxt1),
-	    sep([text("cond"),
-		 nest(Ctxt1#ctxt.sub_indent, D),
-		 text("end")]);
-
 	fun_expr ->
 	    Ctxt1 = reset_prec(Ctxt),
 	    D = lay_clauses(erl_syntax:fun_expr_clauses(Node),
diff --git a/lib/syntax_tools/src/erl_syntax.erl b/lib/syntax_tools/src/erl_syntax.erl
index 1be644c620..251c89a86c 100644
--- a/lib/syntax_tools/src/erl_syntax.erl
+++ b/lib/syntax_tools/src/erl_syntax.erl
@@ -183,8 +183,6 @@
 	 comment/2,
 	 comment_padding/1,
 	 comment_text/1,
-	 cond_expr/1,
-	 cond_expr_clauses/1,
 	 conjunction/1,
 	 conjunction_body/1,
          constrained_function_type/2,
@@ -494,39 +492,38 @@
 %%   <td>class_qualifier</td>
 %%   <td>clause</td>
 %%   <td>comment</td>
-%%   <td>cond_expr</td>
-%%  </tr><tr>
 %%   <td>conjunction</td>
+%%  </tr><tr>
 %%   <td>constrained_function_type</td>
 %%   <td>constraint</td>
 %%   <td>disjunction</td>
-%%  </tr><tr>
 %%   <td>eof_marker</td>
+%%  </tr><tr>
 %%   <td>error_marker</td>
 %%   <td>float</td>
 %%   <td>form_list</td>
-%%  </tr><tr>
 %%   <td>fun_expr</td>
+%%  </tr><tr>
 %%   <td>fun_type</td>
 %%   <td>function</td>
 %%   <td>function_type</td>
-%%  </tr><tr>
 %%   <td>generator</td>
+%%  </tr><tr>
 %%   <td>if_expr</td>
 %%   <td>implicit_fun</td>
 %%   <td>infix_expr</td>
-%%  </tr><tr>
 %%   <td>integer</td>
+%%  </tr><tr>
 %%   <td>integer_range_type</td>
 %%   <td>list</td>
 %%   <td>list_comp</td>
-%%  </tr><tr>
 %%   <td>macro</td>
+%%  </tr><tr>
 %%   <td>map_expr</td>
 %%   <td>map_field_assoc</td>
 %%   <td>map_field_exact</td>
-%%  </tr><tr>
 %%   <td>map_type</td>
+%%  </tr><tr>
 %%   <td>map_type_assoc</td>
 %%   <td>map_type_exact</td>
 %%   <td>match_expr</td>
@@ -556,6 +553,7 @@
 %%   <td>tuple_type</td>
 %%   <td>typed_record_field</td>
 %%   <td>type_application</td>
+%%  </tr><tr>
 %%   <td>type_union</td>
 %%   <td>underscore</td>
 %%   <td>user_type_application</td>
@@ -587,7 +585,6 @@
 %% @see class_qualifier/2
 %% @see clause/3
 %% @see comment/2
-%% @see cond_expr/1
 %% @see conjunction/1
 %% @see constrained_function_type/2
 %% @see constraint/2
@@ -673,7 +670,6 @@ type(Node) ->
 	%% Composite types
 	{'case', _, _, _} -> case_expr;
 	{'catch', _, _} -> catch_expr;
-	{'cond', _, _} -> cond_expr;
 	{'fun', _, {clauses, _}} -> fun_expr;
 	{named_fun, _, _, _} -> named_fun_expr;
 	{'fun', _, {function, _, _}} -> implicit_fun;
@@ -6290,7 +6286,6 @@ if_expr_clauses(Node) ->
 %% @see case_expr_argument/1
 %% @see clause/3
 %% @see if_expr/1
-%% @see cond_expr/1
 
 -record(case_expr, {argument :: syntaxTree(), clauses :: [syntaxTree()]}).
 
@@ -6357,60 +6352,6 @@ case_expr_clauses(Node) ->
 
 
 %% =====================================================================
-%% @doc Creates an abstract cond-expression. If `Clauses' is
-%% `[C1, ..., Cn]', the result represents "<code>cond
-%% <em>C1</em>; ...; <em>Cn</em> end</code>". More exactly, if each
-%% `Ci' represents "<code>() <em>Ei</em> ->
-%% <em>Bi</em></code>", then the result represents "<code>cond
-%% <em>E1</em> -> <em>B1</em>; ...; <em>En</em> -> <em>Bn</em>
-%% end</code>".
-%%
-%% @see cond_expr_clauses/1
-%% @see clause/3
-%% @see case_expr/2
-
-%% type(Node) = cond_expr
-%% data(Node) = Clauses
-%%
-%%	Clauses = [syntaxTree()]
-%%
-%% `erl_parse' representation:
-%%
-%% {'cond', Pos, Clauses}
-%%
-%%	Clauses = [Clause] \ []
-%%	Clause = {clause, ...}
-%%
-%%	See `clause' for documentation on `erl_parse' clauses.
-
--spec cond_expr([syntaxTree()]) -> syntaxTree().
-
-cond_expr(Clauses) ->
-    tree(cond_expr, Clauses).
-
-revert_cond_expr(Node) ->
-    Pos = get_pos(Node),
-    Clauses = [revert_clause(C) || C <- cond_expr_clauses(Node)],
-    {'cond', Pos, Clauses}.
-
-
-%% =====================================================================
-%% @doc Returns the list of clause subtrees of a `cond_expr' node.
-%%
-%% @see cond_expr/1
-
--spec cond_expr_clauses(syntaxTree()) -> [syntaxTree()].
-
-cond_expr_clauses(Node) ->
-    case unwrap(Node) of
-	{'cond', _, Clauses} ->
-	    Clauses;
-	Node1 ->
-	    data(Node1)
-    end.
-
-
-%% =====================================================================
 %% @equiv receive_expr(Clauses, none, [])
 
 -spec receive_expr([syntaxTree()]) -> syntaxTree().
@@ -7534,8 +7475,6 @@ revert_root(Node) ->
 	    revert_char(Node);
 	clause ->
 	    revert_clause(Node);
-	cond_expr ->
-	    revert_cond_expr(Node);
         constrained_function_type ->
             revert_constrained_function_type(Node);
         constraint ->
@@ -7802,8 +7741,6 @@ subtrees(T) ->
 			    [clause_patterns(T), [G],
 			     clause_body(T)]
 		    end;
-		cond_expr ->
-		    [cond_expr_clauses(T)];
 		conjunction ->
 		    [conjunction_body(T)];
                 constrained_function_type ->
@@ -8017,7 +7954,6 @@ make_tree(class_qualifier, [[A], [B]]) -> class_qualifier(A, B);
 make_tree(class_qualifier, [[A], [B], [C]]) -> class_qualifier(A, B, C);
 make_tree(clause, [P, B]) -> clause(P, none, B);
 make_tree(clause, [P, [G], B]) -> clause(P, G, B);
-make_tree(cond_expr, [C]) -> cond_expr(C);
 make_tree(conjunction, [E]) -> conjunction(E);
 make_tree(constrained_function_type, [[F],C]) ->
     constrained_function_type(F, C);
diff --git a/lib/syntax_tools/src/erl_syntax_lib.erl b/lib/syntax_tools/src/erl_syntax_lib.erl
index 352165893f..6185007235 100644
--- a/lib/syntax_tools/src/erl_syntax_lib.erl
+++ b/lib/syntax_tools/src/erl_syntax_lib.erl
@@ -528,8 +528,6 @@ vann(Tree, Env) ->
             vann_case_expr(Tree, Env);
         if_expr ->
             vann_if_expr(Tree, Env);
-        cond_expr ->
-            vann_cond_expr(Tree, Env);
         receive_expr ->
             vann_receive_expr(Tree, Env);
         catch_expr ->
@@ -613,9 +611,6 @@ vann_if_expr(Tree, Env) ->
     Tree1 = rewrite(Tree, erl_syntax:if_expr(Cs1)),
     {ann_bindings(Tree1, Env, Bound, Free), Bound, Free}.
 
-vann_cond_expr(_Tree, _Env) ->
-    erlang:error({not_implemented,cond_expr}).
-
 vann_catch_expr(Tree, Env) ->
     E = erl_syntax:catch_expr_body(Tree),
     {E1, _, Free} = vann(E, Env),
diff --git a/lib/syntax_tools/src/erl_tidy.erl b/lib/syntax_tools/src/erl_tidy.erl
index 5623aa6af3..1ced48ecb3 100644
--- a/lib/syntax_tools/src/erl_tidy.erl
+++ b/lib/syntax_tools/src/erl_tidy.erl
@@ -1551,18 +1551,6 @@ visit_match_body(Ps, P, B, Tree, Env, St0) ->
                 false ->
                     visit_match_expr_final(P, B, Tree, Env, St0)
             end;
-        cond_expr ->
-            Cs = erl_syntax:cond_expr_clauses(B),
-            case multival_clauses(Cs, length(Ps), Ps) of
-                {true, Cs1} ->
-                    report_export_vars(Env#env.file,
-				       erl_syntax:get_pos(B),
-				       "cond", Env#env.verbosity),
-                    Tree1 = erl_syntax:cond_expr(Cs1),
-                    {rewrite(Tree, Tree1), St0};
-                false ->
-                    visit_match_expr_final(P, B, Tree, Env, St0)
-            end;
         receive_expr ->
             %% Handle the timeout case as an extra clause.
             As = erl_syntax:receive_expr_action(B),