Rename allows_underscores to allows_dashes.

src/cargo/core/compiler/context/compilation_files.rs

@@ -305,7 +305,7 @@ impl<'a, 'cfg: 'a> CompilationFiles<'a, 'cfg> {
 
     /// Returns the bin filename for a given target, without extension and metadata.
     fn bin_stem(&self, unit: &Unit<'_>) -> String {
-        if unit.target.allows_underscores() {
+        if unit.target.allows_dashes() {
             unit.target.name().to_string()
         } else {
             unit.target.crate_name()

src/cargo/core/compiler/mod.rs

@@ -193,7 +193,7 @@ fn rustc<'a, 'cfg>(
     // don't pass the `-l` flags.
     let pass_l_flag = unit.target.is_lib() || !unit.pkg.targets().iter().any(|t| t.is_lib());
     let pass_cdylib_link_args = unit.target.is_cdylib();
-    let do_rename = unit.target.allows_underscores() && !unit.mode.is_any_test();
+    let do_rename = unit.target.allows_dashes() && !unit.mode.is_any_test();
     let real_name = unit.target.name().to_string();
     let crate_name = unit.target.crate_name();
 

src/cargo/core/manifest.rs

@@ -792,7 +792,11 @@ impl Target {
         }
     }
 
-    pub fn allows_underscores(&self) -> bool {
+    /// Whether or not this target allows dashes in its filename.
+    ///
+    /// Rustc will always emit filenames with underscores, and Cargo will
+    /// rename them back to dashes if this is true.
+    pub fn allows_dashes(&self) -> bool {
         self.is_bin() || self.is_example() || self.is_custom_build()
     }