From 73f3fa81dc376d5f68e39045d5cb9977db454962 Mon Sep 17 00:00:00 2001
From: tserg <8017125+tserg@users.noreply.github.com>
Date: Thu, 27 Jul 2023 15:55:21 +0800
Subject: [PATCH 1/9] remove code

---
 vyper/codegen/core.py                        | 26 --------------------
 vyper/codegen/function_definitions/common.py |  5 ----
 2 files changed, 31 deletions(-)

diff --git a/vyper/codegen/core.py b/vyper/codegen/core.py
index e1d3ea12b4..3ecd4db697 100644
--- a/vyper/codegen/core.py
+++ b/vyper/codegen/core.py
@@ -1044,32 +1044,6 @@ def is_return_from_function(node):
     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.
diff --git a/vyper/codegen/function_definitions/common.py b/vyper/codegen/function_definitions/common.py
index 3fd5ce0b29..7216fc76f2 100644
--- a/vyper/codegen/function_definitions/common.py
+++ b/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.global_context import GlobalContext
@@ -101,10 +100,6 @@ 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

From 2c76c947969d924fb53622c89c041d92289d3f9e Mon Sep 17 00:00:00 2001
From: tserg <8017125+tserg@users.noreply.github.com>
Date: Thu, 27 Jul 2023 16:01:49 +0800
Subject: [PATCH 2/9] fix lint

---
 vyper/codegen/core.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/vyper/codegen/core.py b/vyper/codegen/core.py
index 3ecd4db697..e16d49972e 100644
--- a/vyper/codegen/core.py
+++ b/vyper/codegen/core.py
@@ -6,7 +6,7 @@
 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,

From 55c7df39bb0c84f848c4228a819c02e13c8bf870 Mon Sep 17 00:00:00 2001
From: tserg <8017125+tserg@users.noreply.github.com>
Date: Thu, 27 Jul 2023 17:39:17 +0800
Subject: [PATCH 3/9] handle exceptions; remove dead helper

---
 vyper/codegen/core.py             | 12 ------------
 vyper/codegen/stmt.py             |  4 ++--
 vyper/semantics/analysis/local.py | 23 +++++++++++++++++++++--
 3 files changed, 23 insertions(+), 16 deletions(-)

diff --git a/vyper/codegen/core.py b/vyper/codegen/core.py
index e16d49972e..1c9c0b671c 100644
--- a/vyper/codegen/core.py
+++ b/vyper/codegen/core.py
@@ -1,7 +1,6 @@
 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
@@ -1033,17 +1032,6 @@ 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
-
-
 def mzero(dst, nbytes):
     # calldatacopy from past-the-end gives zero bytes.
     # cf. YP H.2 (ops section) with CALLDATACOPY spec.
diff --git a/vyper/codegen/stmt.py b/vyper/codegen/stmt.py
index 86ea1813ea..e4493ac461 100644
--- a/vyper/codegen/stmt.py
+++ b/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,
@@ -25,6 +24,7 @@
 from vyper.codegen.return_ import make_return_stmt
 from vyper.evm.address_space import MEMORY, STORAGE
 from vyper.exceptions import CompilerPanic, StructureException, TypeCheckFailure
+from vyper.semantics.analysis.local import is_terminus_node
 from vyper.semantics.types import DArrayT, MemberFunctionT
 from vyper.semantics.types.shortcuts import INT256_T, UINT256_T
 
@@ -425,7 +425,7 @@ def parse_stmt(stmt, context):
 def _is_terminated(code):
     last_stmt = code[-1]
 
-    if is_return_from_function(last_stmt):
+    if is_terminus_node(last_stmt):
         return True
 
     if isinstance(last_stmt, vy_ast.If):
diff --git a/vyper/semantics/analysis/local.py b/vyper/semantics/analysis/local.py
index c0c05325f2..ea17eccf29 100644
--- a/vyper/semantics/analysis/local.py
+++ b/vyper/semantics/analysis/local.py
@@ -65,7 +65,7 @@ def validate_functions(vy_module: vy_ast.Module) -> None:
     err_list.raise_if_not_empty()
 
 
-def _is_terminus_node(node: vy_ast.VyperNode) -> bool:
+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):
@@ -76,8 +76,27 @@ def _is_terminus_node(node: vy_ast.VyperNode) -> bool:
 
 
 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 is_terminus_node(n):
+            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

From 5f605133f0737590b0ab69e4247fa17de970849c Mon Sep 17 00:00:00 2001
From: tserg <8017125+tserg@users.noreply.github.com>
Date: Thu, 19 Oct 2023 15:58:26 +0800
Subject: [PATCH 4/9] move is_terminus_node to analysis utils

---
 vyper/codegen/stmt.py             |  2 +-
 vyper/semantics/analysis/local.py | 11 +----------
 vyper/semantics/analysis/utils.py | 10 ++++++++++
 3 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/vyper/codegen/stmt.py b/vyper/codegen/stmt.py
index bcad8af4cd..b11fc1203d 100644
--- a/vyper/codegen/stmt.py
+++ b/vyper/codegen/stmt.py
@@ -24,7 +24,7 @@
 from vyper.codegen.return_ import make_return_stmt
 from vyper.evm.address_space import MEMORY, STORAGE
 from vyper.exceptions import CompilerPanic, StructureException, TypeCheckFailure
-from vyper.semantics.analysis.local import is_terminus_node
+from vyper.semantics.analysis.utils import is_terminus_node
 from vyper.semantics.types import DArrayT, MemberFunctionT
 from vyper.semantics.types.shortcuts import INT256_T, UINT256_T
 
diff --git a/vyper/semantics/analysis/local.py b/vyper/semantics/analysis/local.py
index ba671f9666..18b13ff69e 100644
--- a/vyper/semantics/analysis/local.py
+++ b/vyper/semantics/analysis/local.py
@@ -26,6 +26,7 @@
     get_exact_type_from_node,
     get_expr_info,
     get_possible_types_from_node,
+    is_terminus_node,
     validate_expected_type,
 )
 from vyper.semantics.data_locations import DataLocation
@@ -65,16 +66,6 @@ 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:
     terminus_nodes = []
 
diff --git a/vyper/semantics/analysis/utils.py b/vyper/semantics/analysis/utils.py
index 4f911764e0..a79e6ba5fe 100644
--- a/vyper/semantics/analysis/utils.py
+++ b/vyper/semantics/analysis/utils.py
@@ -498,6 +498,16 @@ def get_common_types(*nodes: vy_ast.VyperNode, filter_fn: Callable = None) -> Li
     return common_types
 
 
+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
+
+
 # TODO push this into `ArrayT.validate_literal()`
 def _validate_literal_array(node, expected):
     # validate that every item within an array has the same type

From 881bbb19d88686dc8377103cf2669b4593e9688f Mon Sep 17 00:00:00 2001
From: tserg <8017125+tserg@users.noreply.github.com>
Date: Tue, 2 Jan 2024 17:24:11 +0800
Subject: [PATCH 5/9] make is_terminus property of ast node

---
 vyper/ast/nodes.py                | 28 ++++++++++++++++++++++++----
 vyper/codegen/stmt.py             |  3 +--
 vyper/semantics/analysis/local.py |  3 +--
 vyper/semantics/analysis/utils.py | 10 ----------
 4 files changed, 26 insertions(+), 18 deletions(-)

diff --git a/vyper/ast/nodes.py b/vyper/ast/nodes.py
index efab5117d4..a681572d7c 100644
--- a/vyper/ast/nodes.py
+++ b/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):
diff --git a/vyper/codegen/stmt.py b/vyper/codegen/stmt.py
index f889068c4a..475ffe3cfc 100644
--- a/vyper/codegen/stmt.py
+++ b/vyper/codegen/stmt.py
@@ -30,7 +30,6 @@
     TypeCheckFailure,
     tag_exceptions,
 )
-from vyper.semantics.analysis.utils import is_terminus_node
 from vyper.semantics.types import DArrayT, MemberFunctionT
 from vyper.semantics.types.function import ContractFunctionT
 from vyper.semantics.types.shortcuts import INT256_T, UINT256_T
@@ -406,7 +405,7 @@ def parse_stmt(stmt, context):
 def _is_terminated(code):
     last_stmt = code[-1]
 
-    if is_terminus_node(last_stmt):
+    if last_stmt.is_terminus:
         return True
 
     if isinstance(last_stmt, vy_ast.If):
diff --git a/vyper/semantics/analysis/local.py b/vyper/semantics/analysis/local.py
index e810c0fccb..5b84e70860 100644
--- a/vyper/semantics/analysis/local.py
+++ b/vyper/semantics/analysis/local.py
@@ -25,7 +25,6 @@
     get_exact_type_from_node,
     get_expr_info,
     get_possible_types_from_node,
-    is_terminus_node,
     validate_expected_type,
 )
 from vyper.semantics.data_locations import DataLocation
@@ -76,7 +75,7 @@ def check_for_terminus(node_list: list) -> bool:
     # Check for invalid code after returns
     last_node_pos = len(node_list) - 1
     for idx, n in enumerate(node_list):
-        if is_terminus_node(n):
+        if n.is_terminus:
             terminus_nodes.append(n)
             if idx < last_node_pos:
                 # is not last statement in body.
diff --git a/vyper/semantics/analysis/utils.py b/vyper/semantics/analysis/utils.py
index 362cb4f4b8..ba1b02b8d6 100644
--- a/vyper/semantics/analysis/utils.py
+++ b/vyper/semantics/analysis/utils.py
@@ -514,16 +514,6 @@ def get_common_types(*nodes: vy_ast.VyperNode, filter_fn: Callable = None) -> Li
     return common_types
 
 
-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
-
-
 # TODO push this into `ArrayT.validate_literal()`
 def _validate_literal_array(node, expected):
     # validate that every item within an array has the same type

From 35bdbb45d20eabb6e99052e04bfe4926a7724fa9 Mon Sep 17 00:00:00 2001
From: tserg <8017125+tserg@users.noreply.github.com>
Date: Wed, 3 Jan 2024 14:03:38 +0800
Subject: [PATCH 6/9] fix expr and call

---
 vyper/ast/nodes.py | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/vyper/ast/nodes.py b/vyper/ast/nodes.py
index a681572d7c..0bd5e4d23a 100644
--- a/vyper/ast/nodes.py
+++ b/vyper/ast/nodes.py
@@ -731,6 +731,10 @@ def is_terminus(self):
 class Expr(Stmt):
     __slots__ = ("value",)
 
+    @property
+    def is_terminus(self):
+        return self.value.is_terminus
+
 
 class Log(Stmt):
     __slots__ = ("value",)
@@ -1313,10 +1317,10 @@ class Call(ExprNode):
     @property
     def is_terminus(self):
         # cursed import cycle!
-        from vyper.builtins.functions import DISPATCH_TABLE
+        from vyper.builtins.functions import get_builtin_functions
 
         func_name = self.func.id
-        builtin_t = DISPATCH_TABLE[func_name]
+        builtin_t = get_builtin_functions().get(func_name)
         return getattr(builtin_t, "_is_terminus", False)
 
     # try checking if this is a builtin, which is foldable

From fec23e7f2872fb9acf9da7f926a35787ad24f05e Mon Sep 17 00:00:00 2001
From: tserg <8017125+tserg@users.noreply.github.com>
Date: Wed, 3 Jan 2024 14:03:44 +0800
Subject: [PATCH 7/9] remove invalid test

---
 tests/functional/codegen/features/test_assert.py | 8 --------
 1 file changed, 8 deletions(-)

diff --git a/tests/functional/codegen/features/test_assert.py b/tests/functional/codegen/features/test_assert.py
index af189e6dca..244f820537 100644
--- a/tests/functional/codegen/features/test_assert.py
+++ b/tests/functional/codegen/features/test_assert.py
@@ -107,14 +107,6 @@ def test():
     assert self.ret1() == 1
     """,
     """
-@internal
-def valid_address(sender: address) -> bool:
-    selfdestruct(sender)
-@external
-def test():
-    assert self.valid_address(msg.sender)
-    """,
-    """
 @external
 def test():
     assert raw_call(msg.sender, b'', max_outsize=1, gas=10, value=1000*1000) == b''

From 25bd14a559d08e0c2e2d4ad43758618f2ada041f Mon Sep 17 00:00:00 2001
From: tserg <8017125+tserg@users.noreply.github.com>
Date: Wed, 3 Jan 2024 14:28:15 +0800
Subject: [PATCH 8/9] fix call name

---
 vyper/ast/nodes.py | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/vyper/ast/nodes.py b/vyper/ast/nodes.py
index 0bd5e4d23a..82afcb9217 100644
--- a/vyper/ast/nodes.py
+++ b/vyper/ast/nodes.py
@@ -1319,7 +1319,10 @@ def is_terminus(self):
         # cursed import cycle!
         from vyper.builtins.functions import get_builtin_functions
 
-        func_name = self.func.id
+        func_name = self.func.get("id")
+        if not func_name:
+            return False
+
         builtin_t = get_builtin_functions().get(func_name)
         return getattr(builtin_t, "_is_terminus", False)
 

From 7b2c74bedde4894583e431d5605ea9cb73e2112d Mon Sep 17 00:00:00 2001
From: Charles Cooper <cooper.charles.m@gmail.com>
Date: Sun, 14 Jan 2024 12:23:10 -0500
Subject: [PATCH 9/9] rewrite function termination detection

fix dead code detection
fix detection of returns after valid branching returns
add tests
---
 .../codegen/features/test_conditionals.py     |  1 -
 .../syntax/test_unbalanced_return.py          | 43 ++++++++++----
 vyper/semantics/analysis/local.py             | 57 +++++++++----------
 3 files changed, 59 insertions(+), 42 deletions(-)

diff --git a/tests/functional/codegen/features/test_conditionals.py b/tests/functional/codegen/features/test_conditionals.py
index 15ccc40bdf..3b0e57eeca 100644
--- a/tests/functional/codegen/features/test_conditionals.py
+++ b/tests/functional/codegen/features/test_conditionals.py
@@ -7,7 +7,6 @@ def foo(i: bool) -> int128:
     else:
         assert 2 != 0
         return 7
-    return 11
     """
 
     c = get_contract_with_gas_estimation(conditional_return_code)
diff --git a/tests/functional/syntax/test_unbalanced_return.py b/tests/functional/syntax/test_unbalanced_return.py
index d1d9732777..d5754f0053 100644
--- a/tests/functional/syntax/test_unbalanced_return.py
+++ b/tests/functional/syntax/test_unbalanced_return.py
@@ -8,7 +8,7 @@
         """
 @external
 def foo() -> int128:
-    pass
+    pass  # missing return
     """,
         FunctionDeclarationException,
     ),
@@ -18,6 +18,7 @@ def foo() -> int128:
 def foo() -> int128:
     if False:
         return 123
+    # missing return
     """,
         FunctionDeclarationException,
     ),
@@ -27,19 +28,19 @@ def foo() -> int128:
 def test() -> int128:
     if 1 == 1 :
         return 1
-        if True:
+        if True:  # unreachable
             return 0
     else:
         assert msg.sender != msg.sender
     """,
-        FunctionDeclarationException,
+        StructureException,
     ),
     (
         """
 @internal
 def valid_address(sender: address) -> bool:
     selfdestruct(sender)
-    return True
+    return True  # unreachable
     """,
         StructureException,
     ),
@@ -48,7 +49,7 @@ def valid_address(sender: address) -> bool:
 @internal
 def valid_address(sender: address) -> bool:
     selfdestruct(sender)
-    a: address = sender
+    a: address = sender  # unreachable
     """,
         StructureException,
     ),
@@ -58,7 +59,7 @@ def valid_address(sender: address) -> bool:
 def valid_address(sender: address) -> bool:
     if sender == empty(address):
         selfdestruct(sender)
-        _sender: address = sender
+        _sender: address = sender  # unreachable
     else:
         return False
     """,
@@ -69,7 +70,7 @@ def valid_address(sender: address) -> bool:
 @internal
 def foo() -> bool:
     raw_revert(b"vyper")
-    return True
+    return True  # unreachable
     """,
         StructureException,
     ),
@@ -78,7 +79,7 @@ def foo() -> bool:
 @internal
 def foo() -> bool:
     raw_revert(b"vyper")
-    x: uint256 = 3
+    x: uint256 = 3  # unreachable
     """,
         StructureException,
     ),
@@ -88,12 +89,35 @@ def foo() -> bool:
 def foo(x: uint256) -> bool:
     if x == 2:
         raw_revert(b"vyper")
-        a: uint256 = 3
+        a: uint256 = 3  # unreachable
     else:
         return False
     """,
         StructureException,
     ),
+    (
+        """
+@internal
+def foo():
+    return
+    return  # unreachable
+    """,
+        StructureException,
+    ),
+    (
+        """
+@internal
+def foo() -> uint256:
+    if block.number % 2 == 0:
+        return 5
+    elif block.number % 3 == 0:
+        return 6
+    else:
+        return 10
+    return 0  # unreachable
+    """,
+        StructureException,
+    ),
 ]
 
 
@@ -154,7 +178,6 @@ def test() -> int128:
     else:
         x = keccak256(x)
         return 1
-    return 1
     """,
     """
 @external
diff --git a/vyper/semantics/analysis/local.py b/vyper/semantics/analysis/local.py
index 5b84e70860..00804bfec9 100644
--- a/vyper/semantics/analysis/local.py
+++ b/vyper/semantics/analysis/local.py
@@ -69,35 +69,28 @@ def validate_functions(vy_module: vy_ast.Module) -> None:
     err_list.raise_if_not_empty()
 
 
-def check_for_terminus(node_list: list) -> bool:
-    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],
-                )
+# finds the terminus node for a list of nodes.
+# raises an exception if any nodes are unreachable
+def find_terminating_node(node_list: list) -> Optional[vy_ast.VyperNode]:
+    ret = None
 
-    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 node_list:
+        if ret is not None:
+            raise StructureException("Unreachable code!", node)
+        if node.is_terminus:
+            ret = node
 
-    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
-        if not check_for_terminus(node.body):
-            continue
-        return True
-    return False
+        if isinstance(node, vy_ast.If):
+            body_terminates = find_terminating_node(node.body)
+
+            else_terminates = None
+            if node.orelse is not None:
+                else_terminates = find_terminating_node(node.orelse)
+
+            if body_terminates is not None and else_terminates is not None:
+                ret = else_terminates
+
+    return ret
 
 
 def _check_iterator_modification(
@@ -213,11 +206,13 @@ def analyze(self):
             self.visit(node)
 
         if self.func.return_type:
-            if not check_for_terminus(self.fn_node.body):
+            if not find_terminating_node(self.fn_node.body):
                 raise FunctionDeclarationException(
-                    f"Missing or unmatched return statements in function '{self.fn_node.name}'",
-                    self.fn_node,
+                    f"Missing return statement in function '{self.fn_node.name}'", self.fn_node
                 )
+        else:
+            # call find_terminator for its unreachable code detection side effect
+            find_terminating_node(self.fn_node.body)
 
         # visit default args
         assert self.func.n_keyword_args == len(self.fn_node.args.defaults)
@@ -519,7 +514,7 @@ def visit_Return(self, node):
                 raise FunctionDeclarationException("Return statement is missing a value", node)
             return
         elif self.func.return_type is None:
-            raise FunctionDeclarationException("Function does not return any values", node)
+            raise FunctionDeclarationException("Function should not return any values", node)
 
         if isinstance(values, vy_ast.Tuple):
             values = values.elements