Support the AlternationPatternNode

2 files changed, 44 insertions, 8 deletions

diff --git a/prism_compile.c b/prism_compile.c
index d26130bd71..0aee358c8b 100644
--- a/prism_compile.c
+++ b/prism_compile.c
@@ -639,9 +639,33 @@ pm_compile_pattern(rb_iseq_t *iseq, const pm_node_t *node, LINK_ANCHOR *const re
       case PM_UNLESS_NODE:
         rb_bug("Unless guards on pattern matching not yet supported.");
         break;
-      case PM_ALTERNATION_PATTERN_NODE:
-        rb_bug("Alternation pattern matching not yet supported.");
+      case PM_ALTERNATION_PATTERN_NODE: {
+        // Alternation patterns allow you to specify multiple patterns in a
+        // single expression using the | operator.
+        pm_alternation_pattern_node_t *cast = (pm_alternation_pattern_node_t *) node;
+
+        LABEL *matched_left_label = NEW_LABEL(lineno);
+        LABEL *unmatched_left_label = NEW_LABEL(lineno);
+
+        // First, we're going to attempt to match against the left pattern. If
+        // that pattern matches, then we'll skip matching the right pattern.
+        ADD_INSN(ret, &dummy_line_node, dup);
+        pm_compile_pattern(iseq, cast->left, ret, src, compile_context, matched_left_label, unmatched_left_label);
+
+        // If we get here, then we matched on the left pattern. In this case we
+        // should pop out the duplicate value that we preemptively added to
+        // match against the right pattern and then jump to the match label.
+        ADD_LABEL(ret, matched_left_label);
+        ADD_INSN(ret, &dummy_line_node, pop);
+        ADD_INSNL(ret, &dummy_line_node, jump, matched_label);
+        ADD_INSN(ret, &dummy_line_node, putnil);
+
+        // If we get here, then we didn't match on the left pattern. In this
+        // case we attempt to match against the right pattern.
+        ADD_LABEL(ret, unmatched_left_label);
+        pm_compile_pattern(iseq, cast->right, ret, src, compile_context, matched_label, unmatched_label);
         break;
+      }
       case PM_CAPTURE_PATTERN_NODE:
         rb_bug("Capture pattern matching not yet supported.");
         break;
diff --git a/test/ruby/test_compile_prism.rb b/test/ruby/test_compile_prism.rb
index c74ecfef8c..d3fdfd68f1 100644
--- a/test/ruby/test_compile_prism.rb
+++ b/test/ruby/test_compile_prism.rb
@@ -338,6 +338,13 @@ module Prism
     # Pattern matching                                                         #
     ############################################################################
 
+    def test_AlternationPatternNode
+      test_prism_eval("1 in 1 | 2")
+      test_prism_eval("1 in 2 | 1")
+      test_prism_eval("1 in 2 | 3 | 4 | 1")
+      test_prism_eval("1 in 2 | 3")
+    end
+
     def test_MatchPredicateNode
       test_prism_eval("1 in 1")
       test_prism_eval("1.0 in 1.0")
@@ -355,11 +362,6 @@ module Prism
       test_prism_eval("5 in 0..10")
       test_prism_eval("5 in 0...10")
 
-      test_prism_eval("module Prism; @@prism = 1; 1 in ^@@prism; end")
-      test_prism_eval("module Prism; @prism = 1; 1 in ^@prism; end")
-      test_prism_eval("$prism = 1; 1 in ^$prism")
-      test_prism_eval("prism = 1; 1 in ^prism")
-
       test_prism_eval("[\"5\"] in %w[5]")
 
       test_prism_eval("Prism in Prism")
@@ -370,11 +372,21 @@ module Prism
       test_prism_eval("\"foo\" in /.../")
       test_prism_eval("\"foo1\" in /...\#{1}/")
       test_prism_eval("4 in ->(v) { v.even? }")
-      test_prism_eval("4 in ^(4)")
 
       test_prism_eval("1 in 2")
     end
 
+    def test_PinnedExpressionNode
+      test_prism_eval("4 in ^(4)")
+    end
+
+    def test_PinnedVariableNode
+      test_prism_eval("module Prism; @@prism = 1; 1 in ^@@prism; end")
+      test_prism_eval("module Prism; @prism = 1; 1 in ^@prism; end")
+      test_prism_eval("$prism = 1; 1 in ^$prism")
+      test_prism_eval("prism = 1; 1 in ^prism")
+    end
+
     private
 
     def compare_eval(source)