Document a few things

Author: bjorn3

compiler/rustc_driver/src/lib.rs

@@ -132,6 +132,7 @@ pub fn diagnostics_registry() -> Registry {
     Registry::new(&rustc_error_codes::DIAGNOSTICS)
 }
 
+/// This is the primary entry point for rustc.
 pub struct RunCompiler<'a, 'b> {
     at_args: &'a [String],
     callbacks: &'b mut (dyn Callbacks + Send),
@@ -145,6 +146,8 @@ impl<'a, 'b> RunCompiler<'a, 'b> {
     pub fn new(at_args: &'a [String], callbacks: &'b mut (dyn Callbacks + Send)) -> Self {
         Self { at_args, callbacks, file_loader: None, emitter: None, make_codegen_backend: None }
     }
+
+    /// Set a custom codegen backend.
     pub fn set_make_codegen_backend(
         &mut self,
         make_codegen_backend: Option<
@@ -154,17 +157,23 @@ impl<'a, 'b> RunCompiler<'a, 'b> {
         self.make_codegen_backend = make_codegen_backend;
         self
     }
+
+    /// Emit diagnostics to the specified location.
     pub fn set_emitter(&mut self, emitter: Option<Box<dyn Write + Send>>) -> &mut Self {
         self.emitter = emitter;
         self
     }
+
+    /// Load files from sources other than the file system.
     pub fn set_file_loader(
         &mut self,
         file_loader: Option<Box<dyn FileLoader + Send + Sync>>,
     ) -> &mut Self {
         self.file_loader = file_loader;
         self
     }
+
+    /// Parse args and run the compiler.
     pub fn run(self) -> interface::Result<()> {
         run_compiler(
             self.at_args,
@@ -175,8 +184,6 @@ impl<'a, 'b> RunCompiler<'a, 'b> {
         )
     }
 }
-// Parse args and run the compiler. This is the primary entry point for rustc.
-// The FileLoader provides a way to load files from sources other than the file system.
 fn run_compiler(
     at_args: &[String],
     callbacks: &mut (dyn Callbacks + Send),