Fix ``lineno`` API on nodes

3 files changed, 27 insertions, 14 deletions

diff --git a/astroid/nodes/node_classes.py b/astroid/nodes/node_classes.py
index 93c8d47e..81d7658a 100644
--- a/astroid/nodes/node_classes.py
+++ b/astroid/nodes/node_classes.py
@@ -699,10 +699,10 @@ class Arguments(_base_nodes.AssignTypeNode):
         return None
 
     @cached_property
-    def fromlineno(self):
+    def fromlineno(self) -> int:
         """The first line that this node appears on in the source code.
 
-        :type: int or None
+        Can also return 0 if the line can not be determined.
         """
         lineno = super().fromlineno
         return max(lineno, self.parent.fromlineno or 0)
diff --git a/astroid/nodes/node_ng.py b/astroid/nodes/node_ng.py
index e21a2808..64611aba 100644
--- a/astroid/nodes/node_ng.py
+++ b/astroid/nodes/node_ng.py
@@ -446,15 +446,21 @@ class NodeNG:
     # single node, and they rarely get looked at
 
     @cached_property
-    def fromlineno(self) -> int | None:
-        """The first line that this node appears on in the source code."""
+    def fromlineno(self) -> int:
+        """The first line that this node appears on in the source code.
+
+        Can also return 0 if the line can not be determined.
+        """
         if self.lineno is None:
             return self._fixed_source_line()
         return self.lineno
 
     @cached_property
-    def tolineno(self) -> int | None:
-        """The last line that this node appears on in the source code."""
+    def tolineno(self) -> int:
+        """The last line that this node appears on in the source code.
+
+        Can also return 0 if the line can not be determined.
+        """
         if self.end_lineno is not None:
             return self.end_lineno
         if not self._astroid_fields:
@@ -466,10 +472,11 @@ class NodeNG:
             return self.fromlineno
         return last_child.tolineno
 
-    def _fixed_source_line(self) -> int | None:
+    def _fixed_source_line(self) -> int:
         """Attempt to find the line that this node appears on.
 
         We need this method since not all nodes have :attr:`lineno` set.
+        Will return 0 if the line number can not be determined.
         """
         line = self.lineno
         _node = self
@@ -482,7 +489,7 @@ class NodeNG:
             while parent and line is None:
                 line = parent.lineno
                 parent = parent.parent
-        return line
+        return line or 0
 
     def block_range(self, lineno):
         """Get a range from the given line number to where this node ends.
diff --git a/astroid/nodes/scoped_nodes/scoped_nodes.py b/astroid/nodes/scoped_nodes/scoped_nodes.py
index 17da7537..018da851 100644
--- a/astroid/nodes/scoped_nodes/scoped_nodes.py
+++ b/astroid/nodes/scoped_nodes/scoped_nodes.py
@@ -1531,8 +1531,11 @@ class FunctionDef(_base_nodes.MultiLineBlockNode, _base_nodes.Statement, Lambda)
         return type_name
 
     @cached_property
-    def fromlineno(self) -> int | None:
-        """The first line that this node appears on in the source code."""
+    def fromlineno(self) -> int:
+        """The first line that this node appears on in the source code.
+
+        Can also return 0 if the line can not be determined.
+        """
         # lineno is the line number of the first decorator, we want the def
         # statement lineno. Similar to 'ClassDef.fromlineno'
         lineno = self.lineno
@@ -1541,7 +1544,7 @@ class FunctionDef(_base_nodes.MultiLineBlockNode, _base_nodes.Statement, Lambda)
                 node.tolineno - node.lineno + 1 for node in self.decorators.nodes
             )
 
-        return lineno
+        return lineno or 0
 
     @cached_property
     def blockstart_tolineno(self):
@@ -2152,8 +2155,11 @@ class ClassDef(
     )
 
     @cached_property
-    def fromlineno(self) -> int | None:
-        """The first line that this node appears on in the source code."""
+    def fromlineno(self) -> int:
+        """The first line that this node appears on in the source code.
+
+        Can also return 0 if the line can not be determined.
+        """
         if not PY38_PLUS or IS_PYPY and PY38 and not PYPY_7_3_11_PLUS:
             # For Python < 3.8 the lineno is the line number of the first decorator.
             # We want the class statement lineno. Similar to 'FunctionDef.fromlineno'
@@ -2164,7 +2170,7 @@ class ClassDef(
                     node.tolineno - node.lineno + 1 for node in self.decorators.nodes
                 )
 
-            return lineno
+            return lineno or 0
         return super().fromlineno
 
     @cached_property