Add let expressions

ditto-lang · Dec 8, 2022 · 80e9365 · 80e9365
1 parent b81bb98
commit 80e9365
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Showing 7 changed files with 4,825 additions and 3,729 deletions.
diff --git a/grammar.js b/grammar.js
@@ -210,7 +210,11 @@ module.exports = grammar({
 
     value_declaration_name: $ => $._name,
 
-    _expression: $ =>
+    _expression: $ => $._expression4,
+
+    _expression4: $ => choice($.expression_let, $._expression3),
+
+    _expression3: $ =>
       choice(
         $.expression_function,
         $.expression_if,
@@ -240,6 +244,23 @@ module.exports = grammar({
         $.expression_unit
       ),
 
+    expression_let: $ =>
+      seq(
+        "let",
+        repeat1($.expression_let_value_declaration),
+        "in",
+        $._expression
+      ),
+
+    expression_let_value_declaration: $ =>
+      seq(
+        field("binder", $._pattern),
+        field("type_annotation", optional($.type_annotation)),
+        "=",
+        field("expression", $._expression),
+        ";"
+      ),
+
     expression_right_pipe: $ =>
       seq(field("lhs", $._expression2), "|>", field("rhs", $._expression1)),
 
@@ -318,7 +339,7 @@ module.exports = grammar({
 
     expression_effect_expression: $ =>
       seq(
-        $._expression,
+        $._expression3, // `let` expressions should parse as `expression_effect_let`
         optional(seq(";", field("rest", $._expression_effect_statement)))
       ),
 

diff --git a/queries/highlights.scm b/queries/highlights.scm
@@ -35,6 +35,7 @@
   "do"
   "alias"
   "let"
+  "in"
 ] @keyword
 
 [
@@ -81,6 +82,7 @@
 
 ; values
 (value_declaration_name) @function
+(pattern_variable) @variable
 (expression_function ("->" @operator))
 (expression_match_arm ("->" @operator))
 ("<-" @operator)

diff --git a/src/grammar.json b/src/grammar.json
@@ -1194,6 +1194,23 @@
       "name": "_name"
     },
     "_expression": {
+      "type": "SYMBOL",
+      "name": "_expression4"
+    },
+    "_expression4": {
+      "type": "CHOICE",
+      "members": [
+        {
+          "type": "SYMBOL",
+          "name": "expression_let"
+        },
+        {
+          "type": "SYMBOL",
+          "name": "_expression3"
+        }
+      ]
+    },
+    "_expression3": {
       "type": "CHOICE",
       "members": [
         {
@@ -1301,6 +1318,75 @@
         }
       ]
     },
+    "expression_let": {
+      "type": "SEQ",
+      "members": [
+        {
+          "type": "STRING",
+          "value": "let"
+        },
+        {
+          "type": "REPEAT1",
+          "content": {
+            "type": "SYMBOL",
+            "name": "expression_let_value_declaration"
+          }
+        },
+        {
+          "type": "STRING",
+          "value": "in"
+        },
+        {
+          "type": "SYMBOL",
+          "name": "_expression"
+        }
+      ]
+    },
+    "expression_let_value_declaration": {
+      "type": "SEQ",
+      "members": [
+        {
+          "type": "FIELD",
+          "name": "binder",
+          "content": {
+            "type": "SYMBOL",
+            "name": "_pattern"
+          }
+        },
+        {
+          "type": "FIELD",
+          "name": "type_annotation",
+          "content": {
+            "type": "CHOICE",
+            "members": [
+              {
+                "type": "SYMBOL",
+                "name": "type_annotation"
+              },
+              {
+                "type": "BLANK"
+              }
+            ]
+          }
+        },
+        {
+          "type": "STRING",
+          "value": "="
+        },
+        {
+          "type": "FIELD",
+          "name": "expression",
+          "content": {
+            "type": "SYMBOL",
+            "name": "_expression"
+          }
+        },
+        {
+          "type": "STRING",
+          "value": ";"
+        }
+      ]
+    },
     "expression_right_pipe": {
       "type": "SEQ",
       "members": [
@@ -1684,7 +1770,7 @@
       "members": [
         {
           "type": "SYMBOL",
-          "name": "_expression"
+          "name": "_expression3"
         },
         {
           "type": "CHOICE",