[ignition, debugger] correctly set position for return with elided bytecode.

test/unittests/interpreter/source-position-table-unittest.cc

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/interpreter/source-position-table.h"
 #include "test/unittests/test-utils.h"
 
 namespace v8 {
@@ skipping 15 matching lines @@
   SourcePositionTableBuilder builder(isolate(), zone());
   for (int i = 0; i < arraysize(offsets); i++) {
     builder.AddStatementPosition(offsets[i], offsets[i]);
   }
 
   // To test correctness, we rely on the assertions in ToSourcePositionTable().
   // (Also below.)
   CHECK(!builder.ToSourcePositionTable().is_null());
 }
 
+TEST_F(SourcePositionTableTest, EncodeStatementDuplicates) {
+  SourcePositionTableBuilder builder(isolate(), zone());
+  for (int i = 0; i < arraysize(offsets); i++) {
+    builder.AddStatementPosition(offsets[i], offsets[i]);
+    builder.AddStatementPosition(
+        offsets[i], offsets[i],
+        (i % 2 == 0) ? SourcePositionTableBuilder::OVERWRITE_DUPLICATE
+                     : SourcePositionTableBuilder::DISCARD_DUPLICATE);
+    builder.AddStatementPosition(offsets[i], offsets[i]);
+    builder.AddStatementPosition(
+        offsets[i], offsets[i],
+        (i % 2 == 0) ? SourcePositionTableBuilder::OVERWRITE_DUPLICATE
+                     : SourcePositionTableBuilder::DISCARD_DUPLICATE);
+  }
+
+  // To test correctness, we rely on the assertions in ToSourcePositionTable().
+  // (Also below.)
+  CHECK(!builder.ToSourcePositionTable().is_null());
+}
+
 TEST_F(SourcePositionTableTest, EncodeExpression) {
   SourcePositionTableBuilder builder(isolate(), zone());
   for (int i = 0; i < arraysize(offsets); i++) {
     builder.AddExpressionPosition(offsets[i], offsets[i]);
   }
   CHECK(!builder.ToSourcePositionTable().is_null());
 }
 
 TEST_F(SourcePositionTableTest, EncodeAscending) {
   SourcePositionTableBuilder builder(isolate(), zone());
@@ skipping 17 matching lines @@
       builder.AddExpressionPosition(accumulator, accumulator);
     }
   }
 
   CHECK(!builder.ToSourcePositionTable().is_null());
 }
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8