Add const block expression (#97)

* Add const block expression

* Fix const block pattern test

Author: GrayJack

corpus/expressions.txt

@@ -753,3 +753,53 @@ const a : A = unsafe { foo() };
     (identifier)
     (type_identifier)
     (unsafe_block (block (call_expression (identifier) (arguments))))))
+
+===========================================
+Inline const or Const blocks as expression
+===========================================
+
+const { 1 + 3 };
+if *x < 0 { const { &4i32.pow(4) } } else { x }
+let three_ranges = [const { (0..=5).into_inner() }; 3];
+
+---
+
+(source_file
+  (const_block
+    body: (block
+      (binary_expression
+        left: (integer_literal)
+        right: (integer_literal))))
+  (empty_statement)
+  (if_expression
+    condition: (binary_expression
+      left: (unary_expression
+        (identifier))
+      right: (integer_literal))
+    consequence: (block
+      (const_block
+        body: (block
+          (reference_expression
+            value: (call_expression
+              function: (field_expression
+                value: (integer_literal)
+                field: (field_identifier))
+              arguments: (arguments
+                (integer_literal)))))))
+    alternative: (else_clause
+      (block
+        (identifier))))
+  (let_declaration
+    pattern: (identifier)
+    value: (array_expression
+      (const_block
+        body: (block
+          (call_expression
+            function: (field_expression
+              value: (parenthesized_expression
+                (range_expression
+                  (integer_literal)
+                  (integer_literal)))
+              field: (field_identifier))
+            arguments: (arguments))))
+      length: (integer_literal))))

corpus/patterns.txt

@@ -310,3 +310,82 @@ fn foo((1 | 2 | 3): u8) {}
   (line_comment)
   (line_comment)
   (line_comment))
+
+===========================================
+Inline const or Const blocks as pattern
+===========================================
+
+fn foo(x: i32) {
+    const CUBE: i32 = 3.pow(3);
+    match x {
+        CUBE => println!("three cubed"),
+        _ => {}
+    }
+}
+
+fn foo(x: i32) {
+    match x {
+        const { 3.pow(3) } => println!("three cubed"),
+        _ => {}
+    }
+}
+
+---
+
+(source_file
+  (function_item
+    name: (identifier)
+    parameters: (parameters
+      (parameter
+        pattern: (identifier)
+        type: (primitive_type)))
+    body: (block
+      (const_item
+        name: (identifier)
+        type: (primitive_type)
+        value: (call_expression
+          function: (field_expression
+            value: (integer_literal)
+            field: (field_identifier))
+          arguments: (arguments
+            (integer_literal))))
+      (match_expression
+        value: (identifier)
+        body: (match_block
+          (match_arm
+            pattern: (match_pattern
+              (identifier))
+            value: (macro_invocation
+              macro: (identifier)
+              (token_tree
+                (string_literal))))
+          (match_arm
+            pattern: (match_pattern)
+            value: (block))))))
+  (function_item
+    name: (identifier)
+    parameters: (parameters
+      (parameter
+        pattern: (identifier)
+        type: (primitive_type)))
+    body: (block
+      (match_expression
+        value: (identifier)
+        body: (match_block
+          (match_arm
+            pattern: (match_pattern
+              (const_block
+                body: (block
+                  (call_expression
+                    function: (field_expression
+                      value: (integer_literal)
+                      field: (field_identifier))
+                    arguments: (arguments
+                      (integer_literal))))))
+            value: (macro_invocation
+              macro: (identifier)
+              (token_tree
+                (string_literal))))
+          (match_arm
+            pattern: (match_pattern)
+            value: (block)))))))

grammar.js

@@ -870,7 +870,8 @@ module.exports = grammar({
       $.while_expression,
       $.while_let_expression,
       $.loop_expression,
-      $.for_expression
+      $.for_expression,
+      $.const_block
     ),
 
     macro_invocation: $ => seq(
@@ -1160,6 +1161,11 @@ module.exports = grammar({
       field('body', $.block)
     ),
 
+    const_block: $ => seq(
+      'const',
+      field('body', $.block)
+    ),
+
     closure_expression: $ => prec(PREC.closure, seq(
       optional('move'),
       field('parameters', $.closure_parameters),
@@ -1240,6 +1246,7 @@ module.exports = grammar({
       $.mut_pattern,
       $.range_pattern,
       $.or_pattern,
+      $.const_block,
       '_'
     ),
 

src/grammar.json

@@ -4829,6 +4829,10 @@
         {
           "type": "SYMBOL",
           "name": "for_expression"
+        },
+        {
+          "type": "SYMBOL",
+          "name": "const_block"
         }
       ]
     },
@@ -6698,6 +6702,23 @@
         }
       ]
     },
+    "const_block": {
+      "type": "SEQ",
+      "members": [
+        {
+          "type": "STRING",
+          "value": "const"
+        },
+        {
+          "type": "FIELD",
+          "name": "body",
+          "content": {
+            "type": "SYMBOL",
+            "name": "block"
+          }
+        }
+      ]
+    },
     "closure_expression": {
       "type": "PREC",
       "value": -1,
@@ -7208,6 +7229,10 @@
           "type": "SYMBOL",
           "name": "or_pattern"
         },
+        {
+          "type": "SYMBOL",
+          "name": "const_block"
+        },
         {
           "type": "STRING",
           "value": "_"

src/node-types.json

@@ -137,6 +137,10 @@
         "type": "compound_assignment_expr",
         "named": true
       },
+      {
+        "type": "const_block",
+        "named": true
+      },
       {
         "type": "continue_expression",
         "named": true
@@ -327,6 +331,10 @@
         "type": "captured_pattern",
         "named": true
       },
+      {
+        "type": "const_block",
+        "named": true
+      },
       {
         "type": "identifier",
         "named": true
@@ -1015,6 +1023,22 @@
       }
     }
   },
+  {
+    "type": "const_block",
+    "named": true,
+    "fields": {
+      "body": {
+        "multiple": false,
+        "required": true,
+        "types": [
+          {
+            "type": "block",
+            "named": true
+          }
+        ]
+      }
+    }
+  },
   {
     "type": "const_item",
     "named": true,