Add if-then-else expressions

corpus/expressions.txt

@@ -70,6 +70,23 @@ mult_args = my_fn(2, "test");
   (assignment_item (identifier) (call (identifier) (integer_literal)))
   (assignment_item (identifier) (call (identifier) (integer_literal) (string_literal))))
 
+================
+If-Then-Else
+================
+
+if_only = if b then i < j endif;
+value_select = if b then i else j endif;
+elseif = if b then i elseif c then j else k endif;
+elseif_no_else = if b then i < j elseif c then j > i endif;
+
+---
+
+(source_file
+  (assignment_item (identifier) (if_then_else (identifier) (binary_operation (identifier) (identifier))))
+  (assignment_item (identifier) (if_then_else (identifier) (identifier) (identifier)))
+  (assignment_item (identifier) (if_then_else (identifier) (identifier) (identifier) (identifier) (identifier)))
+  (assignment_item (identifier) (if_then_else (identifier) (binary_operation (identifier) (identifier)) (identifier) (binary_operation (identifier) (identifier)))))
+
 ================
 Index Expression
 ================

grammar.js

@@ -45,6 +45,7 @@ module.exports = grammar({
 
       $.binary_operation,
       $.call,
+      $.if_then_else,
       $.index_expression,
       $.unary_operation,
       // TODO: Other expression types
@@ -85,6 +86,14 @@ module.exports = grammar({
       ')',
     )),
 
+    if_then_else: $ => seq(
+      "if", $._expression,
+      "then", $._expression,
+      repeat(seq("elseif", $._expression, "then", $._expression)),
+      optional(seq("else", $._expression)),
+      "endif",
+    ),
+
     index_expression: $ => prec(PREC.call, seq(
       field('collection', $._expression),
       '[',

src/grammar.json

@@ -93,6 +93,10 @@
           "type": "SYMBOL",
           "name": "call"
         },
+        {
+          "type": "SYMBOL",
+          "name": "if_then_else"
+        },
         {
           "type": "SYMBOL",
           "name": "index_expression"
@@ -745,6 +749,76 @@
         ]
       }
     },
+    "if_then_else": {
+      "type": "SEQ",
+      "members": [
+        {
+          "type": "STRING",
+          "value": "if"
+        },
+        {
+          "type": "SYMBOL",
+          "name": "_expression"
+        },
+        {
+          "type": "STRING",
+          "value": "then"
+        },
+        {
+          "type": "SYMBOL",
+          "name": "_expression"
+        },
+        {
+          "type": "REPEAT",
+          "content": {
+            "type": "SEQ",
+            "members": [
+              {
+                "type": "STRING",
+                "value": "elseif"
+              },
+              {
+                "type": "SYMBOL",
+                "name": "_expression"
+              },
+              {
+                "type": "STRING",
+                "value": "then"
+              },
+              {
+                "type": "SYMBOL",
+                "name": "_expression"
+              }
+            ]
+          }
+        },
+        {
+          "type": "CHOICE",
+          "members": [
+            {
+              "type": "SEQ",
+              "members": [
+                {
+                  "type": "STRING",
+                  "value": "else"
+                },
+                {
+                  "type": "SYMBOL",
+                  "name": "_expression"
+                }
+              ]
+            },
+            {
+              "type": "BLANK"
+            }
+          ]
+        },
+        {
+          "type": "STRING",
+          "value": "endif"
+        }
+      ]
+    },
     "index_expression": {
       "type": "PREC",
       "value": 15,

src/node-types.json

@@ -35,6 +35,10 @@
           "type": "identifier",
           "named": true
         },
+        {
+          "type": "if_then_else",
+          "named": true
+        },
         {
           "type": "index_expression",
           "named": true
@@ -94,6 +98,10 @@
             "type": "identifier",
             "named": true
           },
+          {
+            "type": "if_then_else",
+            "named": true
+          },
           {
             "type": "index_expression",
             "named": true
@@ -164,6 +172,10 @@
             "type": "identifier",
             "named": true
           },
+          {
+            "type": "if_then_else",
+            "named": true
+          },
           {
             "type": "index_expression",
             "named": true
@@ -344,6 +356,10 @@
             "type": "identifier",
             "named": true
           },
+          {
+            "type": "if_then_else",
+            "named": true
+          },
           {
             "type": "index_expression",
             "named": true
@@ -413,6 +429,10 @@
             "type": "identifier",
             "named": true
           },
+          {
+            "type": "if_then_else",
+            "named": true
+          },
           {
             "type": "index_expression",
             "named": true
@@ -447,6 +467,69 @@
       }
     }
   },
+  {
+    "type": "if_then_else",
+    "named": true,
+    "fields": {},
+    "children": {
+      "multiple": true,
+      "required": true,
+      "types": [
+        {
+          "type": "absent",
+          "named": true
+        },
+        {
+          "type": "array_literal",
+          "named": true
+        },
+        {
+          "type": "binary_operation",
+          "named": true
+        },
+        {
+          "type": "boolean_literal",
+          "named": true
+        },
+        {
+          "type": "call",
+          "named": true
+        },
+        {
+          "type": "float_literal",
+          "named": true
+        },
+        {
+          "type": "identifier",
+          "named": true
+        },
+        {
+          "type": "if_then_else",
+          "named": true
+        },
+        {
+          "type": "index_expression",
+          "named": true
+        },
+        {
+          "type": "integer_literal",
+          "named": true
+        },
+        {
+          "type": "set_literal",
+          "named": true
+        },
+        {
+          "type": "string_literal",
+          "named": true
+        },
+        {
+          "type": "unary_operation",
+          "named": true
+        }
+      ]
+    }
+  },
   {
     "type": "index_expression",
     "named": true,
@@ -483,6 +566,10 @@
             "type": "identifier",
             "named": true
           },
+          {
+            "type": "if_then_else",
+            "named": true
+          },
           {
             "type": "index_expression",
             "named": true
@@ -541,6 +628,10 @@
             "type": "identifier",
             "named": true
           },
+          {
+            "type": "if_then_else",
+            "named": true
+          },
           {
             "type": "index_expression",
             "named": true
@@ -601,6 +692,10 @@
           "type": "identifier",
           "named": true
         },
+        {
+          "type": "if_then_else",
+          "named": true
+        },
         {
           "type": "index_expression",
           "named": true
@@ -709,6 +804,10 @@
           "type": "identifier",
           "named": true
         },
+        {
+          "type": "if_then_else",
+          "named": true
+        },
         {
           "type": "index_expression",
           "named": true
@@ -852,6 +951,18 @@
     "type": "div",
     "named": false
   },
+  {
+    "type": "else",
+    "named": false
+  },
+  {
+    "type": "elseif",
+    "named": false
+  },
+  {
+    "type": "endif",
+    "named": false
+  },
   {
     "type": "escape_sequence",
     "named": true
@@ -868,6 +979,10 @@
     "type": "identifier",
     "named": true
   },
+  {
+    "type": "if",
+    "named": false
+  },
   {
     "type": "in",
     "named": false
@@ -900,6 +1015,10 @@
     "type": "symdiff",
     "named": false
   },
+  {
+    "type": "then",
+    "named": false
+  },
   {
     "type": "true",
     "named": false