Make a directory dedicated to regression tests

I have had a good experience with this pattern in many of my other
libraries.

test_suite/Cargo.toml

@@ -12,6 +12,7 @@ unstable = ["serde/unstable"]
 serde = { path = "../serde" }
 
 [dev-dependencies]
+automod = "1.0"
 fnv = "1.0"
 rustversion = "1.0"
 serde = { path = "../serde", features = ["rc", "derive"] }

test_suite/tests/regression.rs

@@ -0,0 +1,3 @@
+mod regression {
+    automod::dir!("tests/regression");
+}

test_suite/tests/regression/issue2371.rs

@@ -0,0 +1,43 @@
+use serde::Deserialize;
+
+#[derive(Deserialize)]
+pub struct Nested;
+
+#[derive(Deserialize)]
+pub enum ExternallyTagged {
+    Flatten {
+        #[serde(flatten)]
+        nested: Nested,
+        string: &'static str,
+    },
+}
+
+#[derive(Deserialize)]
+#[serde(tag = "tag")]
+pub enum InternallyTagged {
+    Flatten {
+        #[serde(flatten)]
+        nested: Nested,
+        string: &'static str,
+    },
+}
+
+#[derive(Deserialize)]
+#[serde(tag = "tag", content = "content")]
+pub enum AdjacentlyTagged {
+    Flatten {
+        #[serde(flatten)]
+        nested: Nested,
+        string: &'static str,
+    },
+}
+
+#[derive(Deserialize)]
+#[serde(untagged)]
+pub enum UntaggedWorkaround {
+    Flatten {
+        #[serde(flatten)]
+        nested: Nested,
+        string: &'static str,
+    },
+}

test_suite/tests/test_gen.rs

@@ -892,52 +892,3 @@ pub struct RemotePackedNonCopyDef {
 impl Drop for RemotePackedNonCopyDef {
     fn drop(&mut self) {}
 }
-
-//////////////////////////////////////////////////////////////////////////
-
-/// Regression tests for <https://github.com/serde-rs/serde/issues/2371>
-pub mod static_and_flatten {
-    use serde::Deserialize;
-
-    #[derive(Deserialize)]
-    pub struct Nested;
-
-    #[derive(Deserialize)]
-    pub enum ExternallyTagged {
-        Flatten {
-            #[serde(flatten)]
-            nested: Nested,
-            string: &'static str,
-        },
-    }
-
-    #[derive(Deserialize)]
-    #[serde(tag = "tag")]
-    pub enum InternallyTagged {
-        Flatten {
-            #[serde(flatten)]
-            nested: Nested,
-            string: &'static str,
-        },
-    }
-
-    #[derive(Deserialize)]
-    #[serde(tag = "tag", content = "content")]
-    pub enum AdjacentlyTagged {
-        Flatten {
-            #[serde(flatten)]
-            nested: Nested,
-            string: &'static str,
-        },
-    }
-
-    #[derive(Deserialize)]
-    #[serde(untagged)]
-    pub enum UntaggedWorkaround {
-        Flatten {
-            #[serde(flatten)]
-            nested: Nested,
-            string: &'static str,
-        },
-    }
-}