Add if_clause

This lets us visit the first line of a `block_if_statement` as a single
node. It also ensures that the statements inside the `if` appear as
children of the construct in the AST.

Author: inaki-amatria

grammar.js

@@ -90,7 +90,6 @@ module.exports = grammar({
     [$.data_statement, $.identifier],
     [$.data_value, $._expression],
     [$.else_clause],
-    [$.elseif_clause, $.identifier],
     [$.elseif_clause],
     [$.elsewhere_clause],
     [$.intrinsic_type],
@@ -104,6 +103,7 @@ module.exports = grammar({
     [$.preproc_if_in_specification_part, $.program],
     [$._preproc_expression, $._expression],
     [$.coarray_critical_statement, $.identifier],
+    [$.block_if_clause],
   ],
 
   rules: {
@@ -1338,17 +1338,25 @@ module.exports = grammar({
     )),
 
     block_if_statement: $ => seq(
+      $.block_if_clause,
+      repeat($.elseif_clause),
+      optional($.else_clause),
+      optional($.statement_label),
+      $.end_if_statement
+    ),
+
+    block_if_clause: $ => seq(
+      $.if_clause,
+      $.end_of_statement,
+      repeat($._statement),
+    ),
+
+    if_clause: $ => seq(
       optional($.block_label_start_expression),
       caseInsensitive('if'),
       $._parenthesized_expression,
       caseInsensitive('then'),
       optional($._block_label),
-      $.end_of_statement,
-      repeat($._statement),
-      repeat($.elseif_clause),
-      optional($.else_clause),
-      optional($.statement_label),
-      $.end_if_statement
     ),
 
     end_if_statement: $ => seq(

src/grammar.json

@@ -14663,46 +14663,35 @@
     "block_if_statement": {
       "type": "SEQ",
       "members": [
+        {
+          "type": "SYMBOL",
+          "name": "block_if_clause"
+        },
+        {
+          "type": "REPEAT",
+          "content": {
+            "type": "SYMBOL",
+            "name": "elseif_clause"
+          }
+        },
         {
           "type": "CHOICE",
           "members": [
             {
               "type": "SYMBOL",
-              "name": "block_label_start_expression"
+              "name": "else_clause"
             },
             {
               "type": "BLANK"
             }
           ]
         },
-        {
-          "type": "ALIAS",
-          "content": {
-            "type": "PATTERN",
-            "value": "[iI][fF]"
-          },
-          "named": false,
-          "value": "if"
-        },
-        {
-          "type": "SYMBOL",
-          "name": "_parenthesized_expression"
-        },
-        {
-          "type": "ALIAS",
-          "content": {
-            "type": "PATTERN",
-            "value": "[tT][hH][eE][nN]"
-          },
-          "named": false,
-          "value": "then"
-        },
         {
           "type": "CHOICE",
           "members": [
             {
               "type": "SYMBOL",
-              "name": "_block_label"
+              "name": "statement_label"
             },
             {
               "type": "BLANK"
@@ -14711,49 +14700,78 @@
         },
         {
           "type": "SYMBOL",
-          "name": "end_of_statement"
+          "name": "end_if_statement"
+        }
+      ]
+    },
+    "block_if_clause": {
+      "type": "SEQ",
+      "members": [
+        {
+          "type": "SYMBOL",
+          "name": "if_clause"
         },
         {
-          "type": "REPEAT",
-          "content": {
-            "type": "SYMBOL",
-            "name": "_statement"
-          }
+          "type": "SYMBOL",
+          "name": "end_of_statement"
         },
         {
           "type": "REPEAT",
           "content": {
             "type": "SYMBOL",
-            "name": "elseif_clause"
+            "name": "_statement"
           }
-        },
+        }
+      ]
+    },
+    "if_clause": {
+      "type": "SEQ",
+      "members": [
         {
           "type": "CHOICE",
           "members": [
             {
               "type": "SYMBOL",
-              "name": "else_clause"
+              "name": "block_label_start_expression"
             },
             {
               "type": "BLANK"
             }
           ]
         },
+        {
+          "type": "ALIAS",
+          "content": {
+            "type": "PATTERN",
+            "value": "[iI][fF]"
+          },
+          "named": false,
+          "value": "if"
+        },
+        {
+          "type": "SYMBOL",
+          "name": "_parenthesized_expression"
+        },
+        {
+          "type": "ALIAS",
+          "content": {
+            "type": "PATTERN",
+            "value": "[tT][hH][eE][nN]"
+          },
+          "named": false,
+          "value": "then"
+        },
         {
           "type": "CHOICE",
           "members": [
             {
               "type": "SYMBOL",
-              "name": "statement_label"
+              "name": "_block_label"
             },
             {
               "type": "BLANK"
             }
           ]
-        },
-        {
-          "type": "SYMBOL",
-          "name": "end_if_statement"
         }
       ]
     },
@@ -20729,10 +20747,6 @@
     [
       "else_clause"
     ],
-    [
-      "elseif_clause",
-      "identifier"
-    ],
     [
       "elseif_clause"
     ],
@@ -20778,6 +20792,9 @@
     [
       "coarray_critical_statement",
       "identifier"
+    ],
+    [
+      "block_if_clause"
     ]
   ],
   "precedences": [],