core: (rewriting) Fix recursive type conversion in block arguments for nested regions

tests/pattern_rewriter/test_pattern_rewriter.py

@@ -1610,6 +1610,41 @@ def convert_type(self, typ: IntegerType) -> IndexType | None:
     )
 
 
+def test_recursive_type_conversion_in_regions():
+
+    prog = """\
+"builtin.module"() ({
+  "func.func"() <{"function_type" = (memref<2x4xui16>) -> (), "sym_name" = "main", "sym_visibility" = "private"}> ({
+  ^bb0(%arg0 : memref<2x4xui16>):
+    "func.return"() : () -> ()
+  }) : () -> ()
+}) : () -> ()
+"""
+    expected_prog = """\
+"builtin.module"() ({
+  "func.func"() <{"function_type" = (memref<2x4xindex>) -> (), "sym_name" = "main", "sym_visibility" = "private"}> ({
+  ^0(%arg0 : memref<2x4xindex>):
+    "func.return"() : () -> ()
+  }) : () -> ()
+}) : () -> ()
+"""
+
+    class IndexConversion(TypeConversionPattern):
+
+        @attr_type_rewrite_pattern
+        def convert_type(self, typ: IntegerType) -> IndexType:
+            return IndexType()
+
+    rewrite_and_compare(
+        prog,
+        expected_prog,
+        PatternRewriteWalker(IndexConversion(recursive=True)),
+        op_inserted=1,
+        op_removed=1,
+        op_replaced=1,
+    )
+
+
 def test_no_change():
     """Test that doing nothing successfully does not report doing something."""
 

xdsl/pattern_rewriter.py

@@ -521,7 +521,7 @@ def match_and_rewrite(self, op: Operation, rewriter: PatternRewriter):
         for region in op.regions:
             for block in region.blocks:
                 for arg in block.args:
-                    converted = self.convert_type(arg.type)
+                    converted = self._convert_type_rec(arg.type)
                     if converted is not None and converted != arg.type:
                         rewriter.modify_block_argument_type(arg, converted)
         if changed: