From 6724783395ddc3e85d2a223be7257ab108df4ac3 Mon Sep 17 00:00:00 2001
From: Askaholic <askaholic907@gmail.com>
Date: Tue, 13 Oct 2020 13:40:03 -0800
Subject: [PATCH] Change wording of PyDowncastError display implementation

Displays type(obj) instead of repr(obj) and uses `cannot` instead of
`can't`
to be more consistent with existing python error messages.

See discussion at #1212.
---
 guide/src/conversions/traits.md          | 3 +--
 pyo3-derive-backend/src/from_pyobject.rs | 6 +-----
 src/err/mod.rs                           | 7 ++-----
 tests/test_frompyobject.rs               | 2 +-
 tests/test_pyfunction.rs                 | 6 +++---
 5 files changed, 8 insertions(+), 16 deletions(-)

diff --git a/guide/src/conversions/traits.md b/guide/src/conversions/traits.md
index 7d997538..d09a684f 100644
--- a/guide/src/conversions/traits.md
+++ b/guide/src/conversions/traits.md
@@ -171,8 +171,7 @@ enum RustyEnum {
 ```
 
 If the input is neither a string nor an integer, the error message will be:
-`"Can't convert <INPUT> to Union[str, int]"`, where `<INPUT>` is replaced by the type name and
-`repr()` of the input object.
+`"'<INPUT_TYPE>' cannot be converted to 'Union[str, int]'"`.
 
 #### `#[derive(FromPyObject)]` Container Attributes
 - `pyo3(transparent)`
diff --git a/pyo3-derive-backend/src/from_pyobject.rs b/pyo3-derive-backend/src/from_pyobject.rs
index 8d8dc956..5ea0754d 100644
--- a/pyo3-derive-backend/src/from_pyobject.rs
+++ b/pyo3-derive-backend/src/from_pyobject.rs
@@ -73,11 +73,7 @@ impl<'a> Enum<'a> {
         quote!(
             #(#var_extracts)*
             let type_name = obj.get_type().name();
-            let from = obj
-                .repr()
-                .map(|s| format!("{} ({})", s.to_string_lossy(), type_name))
-                .unwrap_or_else(|_| type_name.to_string());
-            let err_msg = format!("Can't convert {} to {}", from, #error_names);
+            let err_msg = format!("'{}' object cannot be converted to '{}'", type_name, #error_names);
             Err(::pyo3::exceptions::PyTypeError::new_err(err_msg))
         )
     }
diff --git a/src/err/mod.rs b/src/err/mod.rs
index 294cbe9b..461a1ad4 100644
--- a/src/err/mod.rs
+++ b/src/err/mod.rs
@@ -490,11 +490,8 @@ impl<'a> std::fmt::Display for PyDowncastError<'a> {
     fn fmt(&self, f: &mut std::fmt::Formatter) -> Result<(), std::fmt::Error> {
         write!(
             f,
-            "Can't convert {} to {}",
-            self.from
-                .repr()
-                .map(|s| s.to_string_lossy())
-                .unwrap_or_else(|_| self.from.get_type().name()),
+            "'{}' object cannot be converted to '{}'",
+            self.from.get_type().name(),
             self.to
         )
     }
diff --git a/tests/test_frompyobject.rs b/tests/test_frompyobject.rs
index 98f2d2b9..24a7322b 100644
--- a/tests/test_frompyobject.rs
+++ b/tests/test_frompyobject.rs
@@ -296,6 +296,6 @@ fn test_err_rename() {
     assert!(f.is_err());
     assert_eq!(
         f.unwrap_err().to_string(),
-        "TypeError: Can't convert {} (dict) to Union[str, uint, int]"
+        "TypeError: 'dict' object cannot be converted to 'Union[str, uint, int]'"
     );
 }
diff --git a/tests/test_pyfunction.rs b/tests/test_pyfunction.rs
index affb768a..1e088955 100644
--- a/tests/test_pyfunction.rs
+++ b/tests/test_pyfunction.rs
@@ -139,14 +139,14 @@ fn test_conversion_error() {
         conversion_error,
         "conversion_error(None, None, None, None)",
         PyTypeError,
-        "argument 'str_arg': Can't convert None to PyString"
+        "argument 'str_arg': 'NoneType' object cannot be converted to 'PyString'"
     );
     py_expect_exception!(
         py,
         conversion_error,
         "conversion_error(100, None, None, None)",
         PyTypeError,
-        "argument 'str_arg': Can't convert 100 to PyString"
+        "argument 'str_arg': 'int' object cannot be converted to 'PyString'"
     );
     py_expect_exception!(
         py,
@@ -160,7 +160,7 @@ fn test_conversion_error() {
         conversion_error,
         "conversion_error('string1', -100, 'string2', None)",
         PyTypeError,
-        "argument 'tuple_arg': Can't convert 'string2' to PyTuple"
+        "argument 'tuple_arg': 'str' object cannot be converted to 'PyTuple'"
     );
     py_expect_exception!(
         py,