[consume] Change how we parse consume to match copy so we properly handle consume used as a name in case stmt as pattern match.

rdar://109413278

Author: gottesmm

Sources/SwiftParser/Expressions.swift

@@ -504,16 +504,16 @@ extension Parser {
 
     case (.consumeKeyword, let handle)?:
       // `consume` is only contextually a keyword, if it's followed by an
-      // identifier or keyword on the same line.
-      let next = peek()
-      if next.isAtStartOfLine {
-        break
-      }
-      if next.rawTokenKind != .identifier,
-        next.rawTokenKind != .dollarIdentifier,
-        next.rawTokenKind != .keyword
-      {
+      // identifier or keyword on the same line. We do this to ensure that we do
+      // not break any copy functions defined by users. This is following with
+      // what we have done for the consume keyword.
+      switch self.peek() {
+      case TokenSpec(.identifier, allowAtStartOfLine: false),
+           TokenSpec(.dollarIdentifier, allowAtStartOfLine: false),
+           TokenSpec(.self, allowAtStartOfLine: false):
         break
+      default:
+        break EXPR_PREFIX // break out of the outer `switch`
       }
 
       let consumeTok = self.eat(handle)

Tests/SwiftParserTest/translated/MoveExprTests.swift

@@ -82,5 +82,20 @@ final class MoveExprTests: XCTestCase {
       """
     )
   }
-}}
+
+  func testConsumeVariableNameInCast() {
+    assertParse(
+      """
+      class ParentKlass {}
+      class SubKlass : ParentKlass {}
+
+      func test(_ x: SubKlass) {
+        switch x {
+        case let consume as ParentKlass:
+          fallthrough
+        }
+      }
+      """)
+  }
+}