Handle deeply nested capture variables syntax err

kddnewton · kddnewton · commit 8d0105824f1c · 2025-11-16T21:30:24.000-05:00
When there are nested capture variables inside of a pattern match
that has an alternation pattern, it is a syntax error. Currently it
only adds a syntax error when it is at the top level of the pattern.
diff --git a/prism/config.yml b/prism/config.yml
@@ -217,7 +217,6 @@ errors:
   - PARAMETER_UNEXPECTED_FWD
   - PARAMETER_UNEXPECTED_NO_KW
   - PARAMETER_WILD_LOOSE_COMMA
-  - PATTERN_ALTERNATIVE_AFTER_CAPTURE
   - PATTERN_ARRAY_MULTIPLE_RESTS
   - PATTERN_CAPTURE_DUPLICATE
   - PATTERN_CAPTURE_IN_ALTERNATIVE
diff --git a/prism/prism.c b/prism/prism.c
diff --git a/prism/templates/src/diagnostic.c.erb b/prism/templates/src/diagnostic.c.erb
@@ -299,7 +299,6 @@ static const pm_diagnostic_data_t diagnostic_messages[PM_DIAGNOSTIC_ID_MAX] = {
     [PM_ERR_PARAMETER_UNEXPECTED_FWD]           = { "unexpected `...` in parameters", PM_ERROR_LEVEL_SYNTAX },
     [PM_ERR_PARAMETER_WILD_LOOSE_COMMA]         = { "unexpected `,` in parameters", PM_ERROR_LEVEL_SYNTAX },
     [PM_ERR_PARAMETER_UNEXPECTED_NO_KW]         = { "unexpected **nil; no keywords marker disallowed after keywords", PM_ERROR_LEVEL_SYNTAX },
-    [PM_ERR_PATTERN_ALTERNATIVE_AFTER_CAPTURE]  = { "alternative pattern after variable capture", PM_ERROR_LEVEL_SYNTAX },
     [PM_ERR_PATTERN_ARRAY_MULTIPLE_RESTS]       = { "unexpected multiple '*' rest patterns in an array pattern", PM_ERROR_LEVEL_SYNTAX },
     [PM_ERR_PATTERN_CAPTURE_DUPLICATE]          = { "duplicated variable name", PM_ERROR_LEVEL_SYNTAX },
     [PM_ERR_PATTERN_CAPTURE_IN_ALTERNATIVE]     = { "variable capture in alternative pattern", PM_ERROR_LEVEL_SYNTAX },
diff --git a/test/.excludes-mmtk/TestPatternMatching.rb b/test/.excludes-mmtk/TestPatternMatching.rb
@@ -0,0 +1 @@
+exclude(:test_alternative_pattern_nested, "Changes here for syntax errors")
diff --git a/test/.excludes-parsey/TestPatternMatching.rb b/test/.excludes-parsey/TestPatternMatching.rb
@@ -0,0 +1 @@
+exclude(:test_alternative_pattern_nested, "Deeply nested captures variables are missing a syntax error")
diff --git a/test/.excludes/TestPatternMatching.rb b/test/.excludes/TestPatternMatching.rb
@@ -0,0 +1 @@
+exclude(:test_alternative_pattern_nested, "Changes here for syntax errors") if RUBY_DESCRIPTION.include?("+GC")
diff --git a/test/prism/errors/pattern-capture-in-alt-array.txt b/test/prism/errors/pattern-capture-in-alt-array.txt
@@ -0,0 +1,4 @@
+1 => [a, b] | 2
+      ^ variable capture in alternative pattern
+         ^ variable capture in alternative pattern
+
diff --git a/test/prism/errors/pattern-capture-in-alt-hash.txt b/test/prism/errors/pattern-capture-in-alt-hash.txt
@@ -0,0 +1,3 @@
+1 => { a: b } | 2
+          ^ variable capture in alternative pattern
+
diff --git a/test/prism/errors/pattern-capture-in-alt-name.txt b/test/prism/errors/pattern-capture-in-alt-name.txt
@@ -0,0 +1,3 @@
+1 => (2 => b) | 2
+           ^ variable capture in alternative pattern
+
diff --git a/test/prism/errors/pattern-capture-in-alt-top.txt b/test/prism/errors/pattern-capture-in-alt-top.txt
@@ -0,0 +1,4 @@
+1 => a | b
+     ^ variable capture in alternative pattern
+         ^ variable capture in alternative pattern
+
diff --git a/test/ruby/test_pattern_matching.rb b/test/ruby/test_pattern_matching.rb
@@ -208,14 +208,37 @@ def test_alternative_pattern
       case 0
       in a | 0
       end
-    }, [], /alternative pattern after variable capture/,
+    }, [], /alternative pattern/,
     success: false)
 
     assert_in_out_err(['-c'], %q{
       case 0
       in 0 | a
       end
-    }, [], /variable capture in alternative pattern/,
+    }, [], /alternative pattern/,
+    success: false)
+  end
+
+  def test_alternative_pattern_nested
+    assert_in_out_err(['-c'], %q{
+      case 0
+      in [a] | 1
+      end
+    }, [], /alternative pattern/,
+    success: false)
+
+    assert_in_out_err(['-c'], %q{
+      case 0
+      in { a: b } | 1
+      end
+    }, [], /alternative pattern/,
+    success: false)
+
+    assert_in_out_err(['-c'], %q{
+      case 0
+      in [{ a: [{ b: [{ c: }] }] }] | 1
+      end
+    }, [], /alternative pattern/,
     success: false)
   end
 

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1 @@`
	`1`	`+exclude(:test_alternative_pattern_nested, "Changes here for syntax errors")`
Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,3 @@`
	`1`	`+1 => { a: b } \| 2`
	`2`	`+ ^ variable capture in alternative pattern`
	`3`	`+`
Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,3 @@`
	`1`	`+1 => (2 => b) \| 2`
	`2`	`+ ^ variable capture in alternative pattern`
	`3`	`+`