Rollup merge of rust-lang#139671 - m-ou-se:proc-macro-span, r=dtolnay

Proc macro span API redesign: Replace proc_macro::SourceFile by Span::{file, local_file}

Simplification/redesign of the unstable proc macro span API, tracked in rust-lang#54725:

Before:

```rust
impl Span {
    pub fn line(&self) -> usize;
    pub fn column(&self) -> usize;
    pub fn source_file(&self) -> SourceFile;
}

#[derive(Clone, Debug, PartialEq, Eq)]
pub struct SourceFile { .. }

impl !Send for SourceFile {}
impl !Sync for SourceFile {}

impl SourceFile {
    pub fn path(&self) -> PathBuf;
    pub fn is_real(&self) -> bool;
}
```

After:

```rust
impl Span {
    pub fn line(&self) -> usize;
    pub fn column(&self) -> usize;
    pub fn file(&self) -> String; // Mapped file name, for display purposes.
    pub fn local_file(&self) -> Option<PathBuf>; // Real file name as it exists on disk.
}
```

This resolves the last blocker for stabilizing these methods. (Stabilizing will be a separate PR with FCP.)

Author: Zalathar

proc_macro/src/bridge/client.rs

@@ -111,12 +111,6 @@ impl Clone for TokenStream {
     }
 }
 
-impl Clone for SourceFile {
-    fn clone(&self) -> Self {
-        self.clone()
-    }
-}
-
 impl Span {
     pub(crate) fn def_site() -> Span {
         Bridge::with(|bridge| bridge.globals.def_site)

proc_macro/src/bridge/mod.rs

@@ -81,23 +81,17 @@ macro_rules! with_api {
                     $self: $S::TokenStream
                 ) -> Vec<TokenTree<$S::TokenStream, $S::Span, $S::Symbol>>;
             },
-            SourceFile {
-                fn drop($self: $S::SourceFile);
-                fn clone($self: &$S::SourceFile) -> $S::SourceFile;
-                fn eq($self: &$S::SourceFile, other: &$S::SourceFile) -> bool;
-                fn path($self: &$S::SourceFile) -> String;
-                fn is_real($self: &$S::SourceFile) -> bool;
-            },
             Span {
                 fn debug($self: $S::Span) -> String;
-                fn source_file($self: $S::Span) -> $S::SourceFile;
                 fn parent($self: $S::Span) -> Option<$S::Span>;
                 fn source($self: $S::Span) -> $S::Span;
                 fn byte_range($self: $S::Span) -> Range<usize>;
                 fn start($self: $S::Span) -> $S::Span;
                 fn end($self: $S::Span) -> $S::Span;
                 fn line($self: $S::Span) -> usize;
                 fn column($self: $S::Span) -> usize;
+                fn file($self: $S::Span) -> String;
+                fn local_file($self: $S::Span) -> Option<String>;
                 fn join($self: $S::Span, other: $S::Span) -> Option<$S::Span>;
                 fn subspan($self: $S::Span, start: Bound<usize>, end: Bound<usize>) -> Option<$S::Span>;
                 fn resolved_at($self: $S::Span, at: $S::Span) -> $S::Span;
@@ -120,7 +114,6 @@ macro_rules! with_api_handle_types {
             'owned:
             FreeFunctions,
             TokenStream,
-            SourceFile,
 
             'interned:
             Span,

proc_macro/src/bridge/server.rs

@@ -82,7 +82,6 @@ with_api_handle_types!(define_server_handles);
 pub trait Types {
     type FreeFunctions: 'static;
     type TokenStream: 'static + Clone;
-    type SourceFile: 'static + Clone;
     type Span: 'static + Copy + Eq + Hash;
     type Symbol: 'static;
 }

proc_macro/src/lib.rs

@@ -491,12 +491,6 @@ impl Span {
         Span(bridge::client::Span::mixed_site())
     }
 
-    /// The original source file into which this span points.
-    #[unstable(feature = "proc_macro_span", issue = "54725")]
-    pub fn source_file(&self) -> SourceFile {
-        SourceFile(self.0.source_file())
-    }
-
     /// The `Span` for the tokens in the previous macro expansion from which
     /// `self` was generated from, if any.
     #[unstable(feature = "proc_macro_span", issue = "54725")]
@@ -546,6 +540,25 @@ impl Span {
         self.0.column()
     }
 
+    /// The path to the source file in which this span occurs, for display purposes.
+    ///
+    /// This might not correspond to a valid file system path.
+    /// It might be remapped, or might be an artificial path such as `"<macro expansion>"`.
+    #[unstable(feature = "proc_macro_span", issue = "54725")]
+    pub fn file(&self) -> String {
+        self.0.file()
+    }
+
+    /// The path to the source file in which this span occurs on disk.
+    ///
+    /// This is the actual path on disk. It is unaffected by path remapping.
+    ///
+    /// This path should not be embedded in the output of the macro; prefer `file()` instead.
+    #[unstable(feature = "proc_macro_span", issue = "54725")]
+    pub fn local_file(&self) -> Option<PathBuf> {
+        self.0.local_file().map(|s| PathBuf::from(s))
+    }
+
     /// Creates a new span encompassing `self` and `other`.
     ///
     /// Returns `None` if `self` and `other` are from different files.
@@ -614,58 +627,6 @@ impl fmt::Debug for Span {
     }
 }
 
-/// The source file of a given `Span`.
-#[unstable(feature = "proc_macro_span", issue = "54725")]
-#[derive(Clone)]
-pub struct SourceFile(bridge::client::SourceFile);
-
-impl SourceFile {
-    /// Gets the path to this source file.
-    ///
-    /// ### Note
-    /// If the code span associated with this `SourceFile` was generated by an external macro, this
-    /// macro, this might not be an actual path on the filesystem. Use [`is_real`] to check.
-    ///
-    /// Also note that even if `is_real` returns `true`, if `--remap-path-prefix` was passed on
-    /// the command line, the path as given might not actually be valid.
-    ///
-    /// [`is_real`]: Self::is_real
-    #[unstable(feature = "proc_macro_span", issue = "54725")]
-    pub fn path(&self) -> PathBuf {
-        PathBuf::from(self.0.path())
-    }
-
-    /// Returns `true` if this source file is a real source file, and not generated by an external
-    /// macro's expansion.
-    #[unstable(feature = "proc_macro_span", issue = "54725")]
-    pub fn is_real(&self) -> bool {
-        // This is a hack until intercrate spans are implemented and we can have real source files
-        // for spans generated in external macros.
-        // https://github.com/rust-lang/rust/pull/43604#issuecomment-333334368
-        self.0.is_real()
-    }
-}
-
-#[unstable(feature = "proc_macro_span", issue = "54725")]
-impl fmt::Debug for SourceFile {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.debug_struct("SourceFile")
-            .field("path", &self.path())
-            .field("is_real", &self.is_real())
-            .finish()
-    }
-}
-
-#[unstable(feature = "proc_macro_span", issue = "54725")]
-impl PartialEq for SourceFile {
-    fn eq(&self, other: &Self) -> bool {
-        self.0.eq(&other.0)
-    }
-}
-
-#[unstable(feature = "proc_macro_span", issue = "54725")]
-impl Eq for SourceFile {}
-
 /// A single token or a delimited sequence of token trees (e.g., `[1, (), ..]`).
 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 #[derive(Clone)]