Handle case/when

Author: kddnewton

lib/syntax_tree/visitor/compiler.rb

@@ -1324,6 +1324,49 @@ def visit_call(node)
         builder.send(node.message.value.to_sym, argc, flag, block_iseq)
       end
 
+      def visit_case(node)
+        visit(node.value) if node.value
+
+        clauses = []
+        else_clause = nil
+
+        current = node.consequent
+
+        while current
+          clauses << current
+
+          if (current = current.consequent).is_a?(Else)
+            else_clause = current
+            break
+          end
+        end
+
+        branches =
+          clauses.map do |clause|
+            visit(clause.arguments)
+            builder.topn(1)
+            builder.send(:===, 1, VM_CALL_FCALL | VM_CALL_ARGS_SIMPLE)
+            [clause, builder.branchif(:label_00)]
+          end
+
+        builder.pop
+
+        if else_clause
+          visit(else_clause)
+        else
+          builder.putnil
+        end
+
+        builder.leave
+
+        branches.each_with_index do |(clause, branchif), index|
+          builder.leave if index != 0
+          branchif[1] = builder.label
+          builder.pop
+          visit(clause)
+        end
+      end
+
       def visit_class(node)
         name = node.constant.constant.value.to_sym
         class_iseq =
@@ -2148,6 +2191,10 @@ def visit_vcall(node)
         builder.send(node.value.value.to_sym, 0, flag)
       end
 
+      def visit_when(node)
+        visit(node.statements)
+      end
+
       def visit_while(node)
         jumps = []
 

test/compiler_test.rb

@@ -268,6 +268,8 @@ class CompilerTest < Minitest::Test
       "until foo do bar end",
       "for i in [1, 2, 3] do i end",
       "foo ? bar : baz",
+      "case foo when bar then 1 end",
+      "case foo when bar then 1 else 2 end",
       # Constructed values
       "foo..bar",
       "foo...bar",