refactor: remove duplicate terminus checking code

vyper/ast/nodes.py

@@ -229,8 +229,6 @@ class VyperNode:
         Field names that, if present, must be set to None or a `SyntaxException`
         is raised. This attribute is used to exclude syntax that is valid in Python
         but not in Vyper.
-    _is_terminus : bool, optional
-        If `True`, indicates that execution halts upon reaching this node.
     _translated_fields : Dict, optional
         Field names that are reassigned if encountered. Used to normalize fields
         across different Python versions.
@@ -380,6 +378,13 @@ def is_literal_value(self):
         """
         return False
 
+    @property
+    def is_terminus(self):
+        """
+        Check if execution halts upon reaching this node.
+        """
+        return False
+
     @property
     def has_folded_value(self):
         """
@@ -717,7 +722,10 @@ class Stmt(VyperNode):
 
 class Return(Stmt):
     __slots__ = ("value",)
-    _is_terminus = True
+
+    @property
+    def is_terminus(self):
+        return True
 
 
 class Expr(Stmt):
@@ -1302,6 +1310,15 @@ def _op(self, left, right):
 class Call(ExprNode):
     __slots__ = ("func", "args", "keywords")
 
+    @property
+    def is_terminus(self):
+        # cursed import cycle!
+        from vyper.builtins.functions import DISPATCH_TABLE
+
+        func_name = self.func.id
+        builtin_t = DISPATCH_TABLE[func_name]
+        return getattr(builtin_t, "_is_terminus", False)
+
     # try checking if this is a builtin, which is foldable
     def _try_fold(self):
         if not isinstance(self.func, Name):
@@ -1483,7 +1500,10 @@ class AugAssign(Stmt):
 class Raise(Stmt):
     __slots__ = ("exc",)
     _only_empty_fields = ("cause",)
-    _is_terminus = True
+
+    @property
+    def is_terminus(self):
+        return True
 
 
 class Assert(Stmt):

vyper/codegen/core.py

@@ -1,12 +1,11 @@
 import contextlib
 from typing import Generator
 
-from vyper import ast as vy_ast
 from vyper.codegen.ir_node import Encoding, IRnode
 from vyper.compiler.settings import OptimizationLevel
 from vyper.evm.address_space import CALLDATA, DATA, IMMUTABLES, MEMORY, STORAGE, TRANSIENT
 from vyper.evm.opcodes import version_check
-from vyper.exceptions import CompilerPanic, StructureException, TypeCheckFailure, TypeMismatch
+from vyper.exceptions import CompilerPanic, TypeCheckFailure, TypeMismatch
 from vyper.semantics.types import (
     AddressT,
     BoolT,
@@ -1035,43 +1034,6 @@ def eval_seq(ir_node):
     return None
 
 
-def is_return_from_function(node):
-    if isinstance(node, vy_ast.Expr) and node.get("value.func.id") in (
-        "raw_revert",
-        "selfdestruct",
-    ):
-        return True
-    if isinstance(node, (vy_ast.Return, vy_ast.Raise)):
-        return True
-    return False
-
-
-# TODO this is almost certainly duplicated with check_terminus_node
-# in vyper/semantics/analysis/local.py
-def check_single_exit(fn_node):
-    _check_return_body(fn_node, fn_node.body)
-    for node in fn_node.get_descendants(vy_ast.If):
-        _check_return_body(node, node.body)
-        if node.orelse:
-            _check_return_body(node, node.orelse)
-
-
-def _check_return_body(node, node_list):
-    return_count = len([n for n in node_list if is_return_from_function(n)])
-    if return_count > 1:
-        raise StructureException(
-            "Too too many exit statements (return, raise or selfdestruct).", node
-        )
-    # Check for invalid code after returns.
-    last_node_pos = len(node_list) - 1
-    for idx, n in enumerate(node_list):
-        if is_return_from_function(n) and idx < last_node_pos:
-            # is not last statement in body.
-            raise StructureException(
-                "Exit statement with succeeding code (that will not execute).", node_list[idx + 1]
-            )
-
-
 def mzero(dst, nbytes):
     # calldatacopy from past-the-end gives zero bytes.
     # cf. YP H.2 (ops section) with CALLDATACOPY spec.

vyper/codegen/function_definitions/common.py

@@ -4,7 +4,6 @@
 
 import vyper.ast as vy_ast
 from vyper.codegen.context import Constancy, Context
-from vyper.codegen.core import check_single_exit
 from vyper.codegen.function_definitions.external_function import generate_ir_for_external_function
 from vyper.codegen.function_definitions.internal_function import generate_ir_for_internal_function
 from vyper.codegen.ir_node import IRnode
@@ -115,10 +114,6 @@ def generate_ir_for_function(
     # generate _FuncIRInfo
     func_t._ir_info = _FuncIRInfo(func_t)
 
-    # Validate return statements.
-    # XXX: This should really be in semantics pass.
-    check_single_exit(code)
-
     callees = func_t.called_functions
 
     # we start our function frame from the largest callee frame

vyper/codegen/stmt.py

@@ -15,7 +15,6 @@
     get_dyn_array_count,
     get_element_ptr,
     getpos,
-    is_return_from_function,
     make_byte_array_copier,
     make_setter,
     pop_dyn_array,
@@ -406,7 +405,7 @@ def parse_stmt(stmt, context):
 def _is_terminated(code):
     last_stmt = code[-1]
 
-    if is_return_from_function(last_stmt):
+    if last_stmt.is_terminus:
         return True
 
     if isinstance(last_stmt, vy_ast.If):

vyper/semantics/analysis/local.py

@@ -69,19 +69,28 @@ def validate_functions(vy_module: vy_ast.Module) -> None:
     err_list.raise_if_not_empty()
 
 
-def _is_terminus_node(node: vy_ast.VyperNode) -> bool:
-    if getattr(node, "_is_terminus", None):
-        return True
-    if isinstance(node, vy_ast.Expr) and isinstance(node.value, vy_ast.Call):
-        func = get_exact_type_from_node(node.value.func)
-        if getattr(func, "_is_terminus", None):
-            return True
-    return False
-
-
 def check_for_terminus(node_list: list) -> bool:
-    if next((i for i in node_list if _is_terminus_node(i)), None):
+    terminus_nodes = []
+
+    # Check for invalid code after returns
+    last_node_pos = len(node_list) - 1
+    for idx, n in enumerate(node_list):
+        if n.is_terminus:
+            terminus_nodes.append(n)
+            if idx < last_node_pos:
+                # is not last statement in body.
+                raise StructureException(
+                    "Exit statement with succeeding code (that will not execute).",
+                    node_list[idx + 1],
+                )
+
+    if len(terminus_nodes) > 1:
+        raise StructureException(
+            "Too many exit statements (return, raise or selfdestruct).", terminus_nodes[-1]
+        )
+    elif len(terminus_nodes) == 1:
         return True
+
     for node in [i for i in node_list if isinstance(i, vy_ast.If)][::-1]:
         if not node.orelse or not check_for_terminus(node.orelse):
             continue