Correct parsing of discrete_choice expressions.

The existing grammar was causing simple expressions to be incorrectly
parsed as a subtype indication.  This change raises the precedence for
a discrete choice expression to address that issue.

Updated the test corpus to reflect the parsing correction.  Additional
test cases were added for discrete choice.

grammar.js

@@ -704,7 +704,7 @@ module.exports = grammar({
       ),
       component_choice_list: $ => choice(                 // RM 4.3.1
          reservedWord('others'),
-         list_of('|', $._name_for_component_choice),
+         list_of('|', prec.dynamic(1, $._name_for_component_choice)),
       ),
       _aggregate: $ => choice(                            // RM 4.3
          $.record_aggregate,
@@ -1148,7 +1148,7 @@ module.exports = grammar({
       ),
       discrete_choice_list: $ => list_of('|', $.discrete_choice),
       discrete_choice: $ => choice(    // ARM 3.8.1
-         $.expression,
+         prec.dynamic(1, $.expression),
          $._subtype_indication,
          $.range_g,
          reservedWord('others'),

src/grammar.json

@@ -3618,8 +3618,12 @@
           "type": "SEQ",
           "members": [
             {
-              "type": "SYMBOL",
+              "type": "PREC_DYNAMIC",
-              "name": "_name_for_component_choice"
+              "value": 1,
+              "content": {
+                "type": "SYMBOL",
+                "name": "_name_for_component_choice"
+              }
             },
             {
               "type": "REPEAT",
@@ -3631,8 +3635,12 @@
                     "value": "|"
                   },
                   {
-                    "type": "SYMBOL",
+                    "type": "PREC_DYNAMIC",
-                    "name": "_name_for_component_choice"
+                    "value": 1,
+                    "content": {
+                      "type": "SYMBOL",
+                      "name": "_name_for_component_choice"
+                    }
                   }
                 ]
               }
@@ -6491,8 +6499,12 @@
       "type": "CHOICE",
       "members": [
         {
-          "type": "SYMBOL",
+          "type": "PREC_DYNAMIC",
-          "name": "expression"
+          "value": 1,
+          "content": {
+            "type": "SYMBOL",
+            "name": "expression"
+          }
         },
         {
           "type": "SYMBOL",

test/corpus/choices.txt

@@ -1,5 +1,5 @@
 ================================================================================
-Discrete Choices and characters
+Discrete Choice expression
 ================================================================================
 
 declare
@@ -36,10 +36,127 @@ end;
           (case_statement_alternative
             (discrete_choice_list
               (discrete_choice
-                (identifier)))
+                (expression
+                  (term
+                    (identifier)))))
             (null_statement))
           (case_statement_alternative
             (discrete_choice_list
               (discrete_choice
-                (character_literal)))
+                (expression
+                  (term
+                    (character_literal)))))
+            (null_statement)))))))
+
+================================================================================
+Discrete Choice subtype indication
+================================================================================
+
+declare
+   Value : Integer := 5;
+begin
+   case Value is
+      when Integer range 1 .. Integer'Last => null;
+      when Integer range 0 .. 0            => null;
+      when others                          => null;
+   end case;
+end;
+
+--------------------------------------------------------------------------------
+(compilation
+  (compilation_unit
+    (block_statement
+      (non_empty_declarative_part
+        (object_declaration
+          name: (identifier)
+          subtype_mark: (identifier)
+          (expression
+            (term
+              (numeric_literal)))))
+      (handled_sequence_of_statements
+        (case_statement
+          (expression
+            (term
+              name: (identifier)))
+          (case_statement_alternative
+            (discrete_choice_list
+              (discrete_choice
+                subtype_mark: (identifier)
+                (range_constraint
+                  (range_g
+                    (term
+                      (numeric_literal))
+                    (term
+                      name: (identifier)
+                      name: (tick)
+                      name: (attribute_designator
+                        (identifier)))))))
+            (null_statement))
+          (case_statement_alternative
+            (discrete_choice_list
+              (discrete_choice
+                subtype_mark: (identifier)
+                (range_constraint
+                  (range_g
+                    (term
+                      (numeric_literal))
+                    (term
+                      (numeric_literal))))))
+            (null_statement))
+          (case_statement_alternative
+            (discrete_choice_list
+              (discrete_choice))
+            (null_statement)))))))
+
+================================================================================
+Discrete Choice range
+================================================================================
+
+declare
+   Value : Character := 'A';
+begin
+   case Value is
+      when 'a' .. 'z' => null;
+      when 'A' .. 'Z' => null;
+      when others     => null;
+   end case;
+end;
+
+--------------------------------------------------------------------------------
+(compilation
+  (compilation_unit
+    (block_statement
+      (non_empty_declarative_part
+        (object_declaration
+          name: (identifier)
+          subtype_mark: (identifier)
+          (expression
+            (term
+              name: (character_literal)))))
+      (handled_sequence_of_statements
+        (case_statement
+          (expression
+            (term
+              name: (identifier)))
+          (case_statement_alternative
+            (discrete_choice_list
+              (discrete_choice
+                (range_g
+                  (term
+                    name: (character_literal))
+                  (term
+                    name: (character_literal)))))
+            (null_statement))
+          (case_statement_alternative
+            (discrete_choice_list
+              (discrete_choice
+                (range_g
+                  (term
+                    name: (character_literal))
+                  (term
+                    name: (character_literal)))))
+            (null_statement))
+            (case_statement_alternative
+              (discrete_choice_list
+                (discrete_choice))
             (null_statement)))))))

test/corpus/records.txt

@@ -394,12 +394,16 @@ end record;
                 (variant
                   (discrete_choice_list
                     (discrete_choice
-                      (identifier)))
+                      (expression
+                        (term
+                          (identifier)))))
                   (component_list))
                 (variant
                   (discrete_choice_list
                     (discrete_choice
-                      (identifier)))
+                      (expression
+                        (term
+                          (identifier)))))
                   (component_list
                     (component_declaration
                       (identifier)
@@ -452,7 +456,9 @@ variants 2
                 (variant
                   (discrete_choice_list
                     (discrete_choice
-                      (identifier)))
+                      (expression
+                        (term
+                          (identifier)))))
                   (component_list
                     (component_declaration
                       (identifier)

test/corpus/statements.txt

@@ -405,9 +405,13 @@ end;
           (case_statement_alternative
             (discrete_choice_list
               (discrete_choice
-                (character_literal))
+                (expression
+                  (term
+                    (character_literal))))
               (discrete_choice
-                (character_literal)))
+                (expression
+                  (term
+                    (character_literal)))))
             (null_statement)))))))
 
 ================================================================================

test/corpus/types.txt

@@ -146,14 +146,18 @@ end P;
             (array_component_association
               (discrete_choice_list
                 (discrete_choice
-                  (identifier)))
+                  (expression
+                    (term
+                      (identifier)))))
               (expression
                 (term
                   (numeric_literal))))
             (array_component_association
               (discrete_choice_list
                 (discrete_choice
-                  (identifier)))
+                  (expression
+                    (term
+                      (identifier)))))
               (expression
                 (term
                   (numeric_literal)))))))