[#41] Case (#42)

Author: jonhue

grammar.js

@@ -112,10 +112,11 @@ module.exports = grammar({
       alias($.compound_abstraction, $.abstraction),
       alias($.compound_assignment, $.assignment),
       alias($.compound_if, $.if),
+      alias($.compound_case, $.case)
     ),
 
     block: $ => choice(
-      seq($._simple_expression, $._newline),
+      seq(optional('then'), $._simple_expression, $._newline),
       seq($._newline, $._indent, repeat1($._expression), $._dedent)
     ),
 
@@ -205,13 +206,8 @@ module.exports = grammar({
       '=>',
       field('body', $._simple_expression)
     )),
-    compound_abstraction: $ => prec.left(choice(
-      alias($.compound_abstraction_branch, $.abstraction_branch),
-      seq(
-        $._indent,
-        repeat1(alias($.compound_abstraction_branch, $.abstraction_branch)),
-        $._dedent
-      )
+    compound_abstraction: $ => prec.left(repeat1(
+      alias($.compound_abstraction_branch, $.abstraction_branch)
     )),
     compound_abstraction_branch: $ => prec.left(seq(
       field('parameters', $.parameters),
@@ -283,7 +279,14 @@ module.exports = grammar({
         $._destructuring_pattern
       )),
       ':=',
-      field('right', $._compound_expression)
+      choice(
+        field('right', $._compound_expression),
+        seq(
+          $._indent,
+          field('right', $._compound_expression),
+          $._dedent
+        )
+      )
     ),
 
     return: $ => prec.right(seq(
@@ -301,18 +304,29 @@ module.exports = grammar({
     compound_if: $ => prec.right(seq(
       'if',
       field('condition', $._simple_expression),
-      'then',
       field('consequence', $.block),
       field('alternatives', alias(repeat($.else_if_clause), $.else_if_clauses)),
       optional(seq('else', field('alternative', $.block)))
     )),
     else_if_clause: $ => seq(
       'else if',
       field('condition', $._simple_expression),
-      'then',
       field('consequence', $.block)
     ),
 
+    compound_case: $ => seq(
+      'case',
+      field('value', $._simple_expression),
+      field('branches', alias(repeat1($.when_clause), $.when_clauses)),
+      optional(seq('else', field('default', $.block)))
+    ),
+    when_clause: $ => seq(
+      'when',
+      field('values', $.expression_list),
+      field('consequence', $.block)
+    ),
+    expression_list: $ => commaSep1($._simple_expression),
+
     map: $ => seq(
       '{',
       commaSep(choice(

test/corpus/expressions.txt

@@ -7,10 +7,10 @@ abstraction
 
 fib :=
   (0) =>
-      0
+    0
   (1) => 1
   (n = 2) =>
-      fib(n - 1) + fib(n - 2)
+    fib(n - 1) + fib(n - 2)
 
 (a) =>
   b := (c) =>
@@ -418,17 +418,18 @@ return (a) =>
 if
 ==================
 
-if false then
+if false
   1
-if true then
+if true
   1
 else
   1
-if true then
-  1
-else if false then 1
-else if true then
-  1
+a :=
+  if true
+    1
+  else if false then 1
+  else if true
+    1
 
 if false then 1
 if true then 1 else 1
@@ -446,19 +447,21 @@ if true then 1 else 1
       (number))
     alternative: (block
       (number)))
-  (if
-    condition: (boolean)
-    consequence: (block
-      (number))
-    alternatives: (else_if_clauses
-      (else_if_clause
-        condition: (boolean)
-        consequence: (block
-          (number)))
-      (else_if_clause
-        condition: (boolean)
-        consequence: (block
-          (number)))))
+  (assignment
+    left: (identifier_pattern)
+    right: (if
+      condition: (boolean)
+      consequence: (block
+        (number))
+      alternatives: (else_if_clauses
+        (else_if_clause
+          condition: (boolean)
+          consequence: (block
+            (number)))
+        (else_if_clause
+          condition: (boolean)
+          consequence: (block
+            (number))))))
   (if
     condition: (boolean)
     consequence: (block
@@ -467,3 +470,47 @@ if true then 1 else 1
     condition: (boolean)
     consequence: (number)
     alternative: (number)))
+
+==================
+case
+==================
+
+a := case a
+     when 1
+       1
+
+case a
+when 1
+  1
+when 1, 1 then 1
+else 1
+
+---
+
+(program
+  (assignment
+    left: (identifier_pattern)
+    right: (case
+      value: (identifier)
+      branches: (when_clauses
+        (when_clause
+          values: (expression_list
+            (number))
+          consequence: (block
+            (number))))))
+  (case
+    value: (identifier)
+    branches: (when_clauses
+      (when_clause
+        values: (expression_list
+          (number))
+        consequence: (block
+          (number)))
+      (when_clause
+        values: (expression_list
+          (number)
+          (number))
+        consequence: (block
+          (number))))
+    default: (block
+      (number))))