Fix `pyreverse` type annotations for attributes using alternative union syntax (#6720)

* Fix `pyreverse` type annotations for attributes using alternative union syntax.

* Fix `dot` output and add additional test cases

* Apply suggestions from code review

* Add changelog entry in `full.rst`

3 files changed, 9 insertions, 10 deletions

diff --git a/pylint/pyreverse/diagrams.py b/pylint/pyreverse/diagrams.py
index 7cd5333f3..7b15bf816 100644
--- a/pylint/pyreverse/diagrams.py
+++ b/pylint/pyreverse/diagrams.py
@@ -159,7 +159,9 @@ class ClassDiagram(Figure, FilterMixIn):
             if isinstance(node, astroid.Instance):
                 node = node._proxied
             if (
-                isinstance(node, (nodes.ClassDef, nodes.Name, nodes.Subscript))
+                isinstance(
+                    node, (nodes.ClassDef, nodes.Name, nodes.Subscript, nodes.BinOp)
+                )
                 and hasattr(node, "name")
                 and not self.has_node(node)
             ):
diff --git a/pylint/pyreverse/dot_printer.py b/pylint/pyreverse/dot_printer.py
index df4e94a00..883682704 100644
--- a/pylint/pyreverse/dot_printer.py
+++ b/pylint/pyreverse/dot_printer.py
@@ -81,24 +81,19 @@ class DotPrinter(Printer):
             f'"{name}" [color="{color}"{fontcolor_part}{label_part}, shape="{shape}", style="{style}"];'
         )
 
-    def _build_label_for_node(
-        self, properties: NodeProperties, is_interface: bool | None = False
-    ) -> str:
+    def _build_label_for_node(self, properties: NodeProperties) -> str:
         if not properties.label:
             return ""
 
         label: str = properties.label
-        if is_interface:
-            # add a stereotype
-            label = "<<interface>>\\n" + label
-
         if properties.attrs is None and properties.methods is None:
             # return a "compact" form which only displays the class name in a box
             return label
 
         # Add class attributes
         attrs: list[str] = properties.attrs or []
-        label = "{" + label + "|" + r"\l".join(attrs) + r"\l|"
+        attrs_string = r"\l".join(attr.replace("|", r"\|") for attr in attrs)
+        label = rf"{{{label}|{attrs_string}\l|"
 
         # Add class methods
         methods: list[nodes.FunctionDef] = properties.methods or []
diff --git a/pylint/pyreverse/utils.py b/pylint/pyreverse/utils.py
index 7052791ec..b1be195e3 100644
--- a/pylint/pyreverse/utils.py
+++ b/pylint/pyreverse/utils.py
@@ -218,7 +218,9 @@ def infer_node(node: nodes.AssignAttr | nodes.AssignName) -> set[Any]:
     ann = get_annotation(node)
     try:
         if ann:
-            if isinstance(ann, nodes.Subscript):
+            if isinstance(ann, nodes.Subscript) or (
+                isinstance(ann, nodes.BinOp) and ann.op == "|"
+            ):
                 return {ann}
             return set(ann.infer())
         return set(node.infer())