Add name_arity as a format_component.

compiler/error_util.m:
    As above.

compiler/prog_data.m:
    To make this possible, move the existing definitions of name_arity here.

compiler/hlds_defns.m:
compiler/pred_table.m:
    Delete two the old copies of that definition.

compiler/error_util.m

@@ -508,6 +508,10 @@
             % The output should contain the string form of the sym_name,
             % surrounded by `' quotes.
 
+    ;       name_arity(name_arity)
+            % The output should contain the name, surrounded by `' quotes,
+            % followed by '/' and the arity.
+
     ;       qual_sym_name_arity(sym_name_arity)
     ;       unqual_sym_name_arity(sym_name_arity)
             % The output should contain the string form of the sym_name,
@@ -2045,6 +2049,10 @@ error_pieces_to_string_2(FirstInMsg, [Component | Components]) = Str :-
         ),
         Word = sym_name_to_word(SymName),
         Str = join_string_and_tail(Word, Components, TailStr)
+    ;
+        Component = name_arity(NameAndArity),
+        Word = name_arity_to_word(NameAndArity),
+        Str = join_string_and_tail(Word, Components, TailStr)
     ;
         (
             Component = qual_sym_name_arity(SymNameAndArity)
@@ -2267,6 +2275,10 @@ convert_components_to_paragraphs_acc(FirstInMsg, [Component | Components],
             SymName = unqualified(unqualify_name(SymName0))
         ),
         RevWords1 = [plain_word(sym_name_to_word(SymName)) | RevWords0]
+    ;
+        Component = name_arity(NameAndArity),
+        Word = name_arity_to_word(NameAndArity),
+        RevWords1 = [plain_word(Word) | RevWords0]
     ;
         (
             Component = qual_sym_name_arity(SymNameAndArity)
@@ -2461,6 +2473,11 @@ join_prefixes([Head | Tail]) = Strings :-
 sym_name_to_word(SymName) =
     add_quotes(sym_name_to_string(SymName)).
 
+:- func name_arity_to_word(name_arity) = string.
+
+name_arity_to_word(name_arity(Name, Arity)) =
+    add_quotes(Name) ++ "/" ++ int_to_string(Arity).
+
 :- func sym_name_arity_to_word(sym_name_arity) = string.
 
 sym_name_arity_to_word(sym_name_arity(SymName, Arity)) =

compiler/hlds_defns.m

@@ -80,9 +80,6 @@
 :- import_module string.
 :- import_module term.
 
-:- type name_arity
-    --->    name_arity(string, arity).
-
 %-----------------------------------------------------------------------------%
 
 write_hlds_defns(Stream, ModuleInfo, !IO) :-

compiler/pred_table.m

@@ -425,8 +425,6 @@
 :- type name_index  == map(string, list(pred_id)).
 
 :- type name_arity_index == map(name_arity, list(pred_id)).
-:- type name_arity
-    --->    name_arity(string, arity).
 
 :- type module_and_name
     --->    module_and_name(module_name, string).

compiler/prog_data.m

@@ -1976,6 +1976,9 @@ valid_trace_grade_name(GradeName) :-
 
 :- interface.
 
+:- type name_arity
+    --->    name_arity(string, arity).
+
 :- type sym_name_specifier
     --->    sym_name_specifier_name(sym_name)
     ;       sym_name_specifier_name_arity(sym_name, arity).