fixup! new lint: source_item_ordering

Author: decryphe

tests/ui-toml/arbitrary_source_item_ordering/bad_conf_3/clippy.toml

@@ -0,0 +1 @@
+source-item-ordering = ["enum", "impl", "module", "struct", "trait", "struct"]

tests/ui-toml/arbitrary_source_item_ordering/default_exp/clippy.toml

@@ -0,0 +1,2 @@
+trait-assoc-item-kinds-order = ["const", "type", "fn"]
+source-item-ordering = ["enum", "impl", "module", "struct", "trait"]

tests/ui-toml/arbitrary_source_item_ordering/ordering_good.bad_conf_3.stderr

@@ -0,0 +1,8 @@
+error: error reading Clippy's configuration file: The category "Struct" was enabled more than once in the source ordering configuration.
+  --> $DIR/tests/ui-toml/arbitrary_source_item_ordering/bad_conf_3/clippy.toml:1:24
+   |
+LL | source-item-ordering = ["enum", "impl", "module", "struct", "trait", "struct"]
+   |                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+

tests/ui-toml/arbitrary_source_item_ordering/ordering_good.rs

@@ -1,8 +1,10 @@
 //@aux-build:../../ui/auxiliary/proc_macros.rs
-//@revisions: default bad_conf_1 bad_conf_2
+//@revisions: default default_exp bad_conf_1 bad_conf_2 bad_conf_3
 //@[default] rustc-env:CLIPPY_CONF_DIR=tests/ui-toml/arbitrary_source_item_ordering/default
+//@[default_exp] rustc-env:CLIPPY_CONF_DIR=tests/ui-toml/arbitrary_source_item_ordering/default_exp
 //@[bad_conf_1] rustc-env:CLIPPY_CONF_DIR=tests/ui-toml/arbitrary_source_item_ordering/bad_conf_1
 //@[bad_conf_2] rustc-env:CLIPPY_CONF_DIR=tests/ui-toml/arbitrary_source_item_ordering/bad_conf_2
+//@[bad_conf_3] rustc-env:CLIPPY_CONF_DIR=tests/ui-toml/arbitrary_source_item_ordering/bad_conf_3
 
 #![allow(dead_code)]
 #![warn(clippy::arbitrary_source_item_ordering)]