Auto merge of rust-lang#3573 - RalfJung:fs-cfg, r=RalfJung

unix/fs: a bit of cleanup around host-specific code

Author: bors

src/tools/miri/src/shims/unix/fs.rs

@@ -137,37 +137,28 @@ trait EvalContextExtPrivate<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx
         &mut self,
         file_type: std::io::Result<FileType>,
     ) -> InterpResult<'tcx, i32> {
+        #[cfg(unix)]
+        use std::os::unix::fs::FileTypeExt;
+
         let this = self.eval_context_mut();
         match file_type {
             Ok(file_type) => {
-                if file_type.is_dir() {
-                    Ok(this.eval_libc("DT_DIR").to_u8()?.into())
-                } else if file_type.is_file() {
-                    Ok(this.eval_libc("DT_REG").to_u8()?.into())
-                } else if file_type.is_symlink() {
-                    Ok(this.eval_libc("DT_LNK").to_u8()?.into())
-                } else {
+                match () {
+                    _ if file_type.is_dir() => Ok(this.eval_libc("DT_DIR").to_u8()?.into()),
+                    _ if file_type.is_file() => Ok(this.eval_libc("DT_REG").to_u8()?.into()),
+                    _ if file_type.is_symlink() => Ok(this.eval_libc("DT_LNK").to_u8()?.into()),
                     // Certain file types are only supported when the host is a Unix system.
-                    // (i.e. devices and sockets) If it is, check those cases, if not, fall back to
-                    // DT_UNKNOWN sooner.
-
                     #[cfg(unix)]
-                    {
-                        use std::os::unix::fs::FileTypeExt;
-                        if file_type.is_block_device() {
-                            Ok(this.eval_libc("DT_BLK").to_u8()?.into())
-                        } else if file_type.is_char_device() {
-                            Ok(this.eval_libc("DT_CHR").to_u8()?.into())
-                        } else if file_type.is_fifo() {
-                            Ok(this.eval_libc("DT_FIFO").to_u8()?.into())
-                        } else if file_type.is_socket() {
-                            Ok(this.eval_libc("DT_SOCK").to_u8()?.into())
-                        } else {
-                            Ok(this.eval_libc("DT_UNKNOWN").to_u8()?.into())
-                        }
-                    }
-                    #[cfg(not(unix))]
-                    Ok(this.eval_libc("DT_UNKNOWN").to_u8()?.into())
+                    _ if file_type.is_block_device() =>
+                        Ok(this.eval_libc("DT_BLK").to_u8()?.into()),
+                    #[cfg(unix)]
+                    _ if file_type.is_char_device() => Ok(this.eval_libc("DT_CHR").to_u8()?.into()),
+                    #[cfg(unix)]
+                    _ if file_type.is_fifo() => Ok(this.eval_libc("DT_FIFO").to_u8()?.into()),
+                    #[cfg(unix)]
+                    _ if file_type.is_socket() => Ok(this.eval_libc("DT_SOCK").to_u8()?.into()),
+                    // Fallback
+                    _ => Ok(this.eval_libc("DT_UNKNOWN").to_u8()?.into()),
                 }
             }
             Err(e) =>
@@ -1314,7 +1305,6 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
         }
     }
 
-    #[cfg_attr(not(unix), allow(unused))]
     fn isatty(
         &mut self,
         miri_fd: &OpTy<'tcx, Provenance>,
@@ -1467,8 +1457,8 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
         #[cfg(unix)]
         {
             use std::os::unix::fs::OpenOptionsExt;
-            fopts.mode(0o600);
             // Do not allow others to read or modify this file.
+            fopts.mode(0o600);
             fopts.custom_flags(libc::O_EXCL);
         }
         #[cfg(windows)]