Added TealSeqError for better error reporting. (#661)

pyteal/__init__.py

@@ -18,6 +18,7 @@
 from pyteal.errors import (
     TealInternalError,
     TealTypeError,
+    TealSeqError,
     TealInputError,
     TealCompileError,
     TealPragmaError,
@@ -47,6 +48,7 @@
         "TealType",
         "TealInternalError",
         "TealTypeError",
+        "TealSeqError",
         "TealInputError",
         "TealCompileError",
         "TealPragmaError",

pyteal/__init__.pyi

@@ -21,6 +21,7 @@ from pyteal.types import TealType
 from pyteal.errors import (
     TealInternalError,
     TealTypeError,
+    TealSeqError,
     TealInputError,
     TealCompileError,
     TealPragmaError,
@@ -210,6 +211,7 @@ __all__ = [
     "TealLabel",
     "TealOp",
     "TealPragmaError",
+    "TealSeqError",
     "TealSimpleBlock",
     "TealType",
     "TealTypeError",

pyteal/ast/seq.py

@@ -1,7 +1,7 @@
 from typing import List, TYPE_CHECKING, overload
 
 from pyteal.types import TealType, require_type
-from pyteal.errors import TealInputError
+from pyteal.errors import TealInputError, TealTypeError, TealSeqError
 from pyteal.ir import TealSimpleBlock
 from pyteal.ast.expr import Expr
 
@@ -51,7 +51,17 @@ def __init__(self, *exprs):
             if not isinstance(expr, Expr):
                 raise TealInputError("{} is not a pyteal expression.".format(expr))
             if i + 1 < len(exprs):
-                require_type(expr, TealType.none)
+                try:
+                    require_type(expr, TealType.none)
+                except TealTypeError:
+                    message = "{} must have a return type of TealType.none. ".format(
+                        expr
+                    )
+                    message += (
+                        "Only the last entry of a Seq array can have a return value."
+                    )
+                    seq_error = TealSeqError(message)
+                    raise seq_error
 
         self.args = exprs
 

pyteal/ast/seq_test.py

@@ -90,13 +90,13 @@ def test_seq_has_return():
 
 
 def test_seq_invalid():
-    with pytest.raises(pt.TealTypeError):
+    with pytest.raises(pt.TealSeqError):
         pt.Seq([pt.Int(1), pt.Pop(pt.Int(2))])
 
-    with pytest.raises(pt.TealTypeError):
+    with pytest.raises(pt.TealSeqError):
         pt.Seq([pt.Int(1), pt.Int(2)])
 
-    with pytest.raises(pt.TealTypeError):
+    with pytest.raises(pt.TealSeqError):
         pt.Seq([pt.Seq([pt.Pop(pt.Int(1)), pt.Int(2)]), pt.Int(3)])
 
 

pyteal/errors.py

@@ -26,6 +26,17 @@ def __str__(self) -> str:
 TealTypeError.__module__ = "pyteal"
 
 
+class TealSeqError(TealTypeError):
+    def __init__(self, message: str) -> None:
+        self.message = message
+
+    def __str__(self):
+        return self.message
+
+
+TealSeqError.__module__ = "pyteal"
+
+
 class TealInputError(Exception):
     def __init__(self, msg: str) -> None:
         self.message = msg