Add test cases for fixed issues (#4189)

Author: ayazhafiz

rustfmt-core/rustfmt-lib/tests/source/issue-3550.rs

@@ -0,0 +1,37 @@
+fn main() {
+    assert(long()
+        .long()
+        .long()
+        .long()
+        .long()
+        .long()
+        .long()
+        .long()
+        .long()
+        .long()
+        .long()
+        .long()
+        .long()
+        .long()
+        .long()
+        .long(),
+    );
+
+    assert!(long()
+        .long()
+        .long()
+        .long()
+        .long()
+        .long()
+        .long()
+        .long()
+        .long()
+        .long()
+        .long()
+        .long()
+        .long()
+        .long()
+        .long()
+        .long(),);
+}
+

rustfmt-core/rustfmt-lib/tests/target/issue-3068.rs

@@ -0,0 +1,14 @@
+// rustfmt-hard_tabs: true
+// rustfmt-single_line_if_else_max_width: 10
+
+macro_rules! foo {
+	($bar: expr, $t: ty) => {
+		$bar(|x| {
+			if x {
+				None
+			} else {
+				None
+			}
+		})
+	};
+}

rustfmt-core/rustfmt-lib/tests/target/issue-3550.rs

@@ -0,0 +1,39 @@
+fn main() {
+    assert(
+        long()
+            .long()
+            .long()
+            .long()
+            .long()
+            .long()
+            .long()
+            .long()
+            .long()
+            .long()
+            .long()
+            .long()
+            .long()
+            .long()
+            .long()
+            .long(),
+    );
+
+    assert!(
+        long()
+            .long()
+            .long()
+            .long()
+            .long()
+            .long()
+            .long()
+            .long()
+            .long()
+            .long()
+            .long()
+            .long()
+            .long()
+            .long()
+            .long()
+            .long(),
+    );
+}

rustfmt-core/rustfmt-lib/tests/target/issue-3638.rs

@@ -0,0 +1,19 @@
+macro_rules! abait {
+    ($x:expr) => {
+        Ok(())
+    };
+}
+
+mod a {
+    fn foo() -> Result<(), ()> {
+        unsafe {
+            (
+                abait!(
+                    proxy.load_account(ahc_client_end, TEST_ACCOUNT_ID.clone().as_mut().into())
+                )?,
+                (),
+            )
+        };
+        Ok(())
+    }
+}

rustfmt-core/rustfmt-lib/tests/target/issue-3858.rs

@@ -0,0 +1,12 @@
+// rustfmt-hard_tabs: true
+
+macro_rules! member_mut {
+	($self:expr, $member:expr) => {{
+		use self::Member::*;
+		let r = &mut *$self;
+		match $member {
+			A => &mut r.a,
+			B => &mut r.b,
+		}
+	}};
+}

rustfmt-core/rustfmt-lib/tests/target/issue-3936.rs

@@ -0,0 +1,9 @@
+// rustfmt-hard_tabs: true
+
+macro_rules! m {
+	($a:expr) => {
+		if $a {
+			return;
+		}
+	};
+}