Add _value methods to proc_macro lib

Author: GuillaumeGomez

library/Cargo.lock

@@ -158,6 +158,10 @@ dependencies = [
  "rustc-std-workspace-core",
 ]
 
+[[package]]
+name = "literal-escaper"
+version = "0.0.1"
+
 [[package]]
 name = "memchr"
 version = "2.7.4"
@@ -220,6 +224,7 @@ name = "proc_macro"
 version = "0.0.0"
 dependencies = [
  "core",
+ "literal-escaper",
  "std",
 ]
 

library/proc_macro/Cargo.toml

@@ -4,6 +4,7 @@ version = "0.0.0"
 edition = "2021"
 
 [dependencies]
+literal-escaper = { path = "../literal-escaper", features = ["rustc-dep-of-std"] }
 std = { path = "../std" }
 # Workaround: when documenting this crate rustdoc will try to load crate named
 # `core` when resolving doc links. Without this line a different `core` will be

library/proc_macro/src/lib.rs

@@ -50,11 +50,22 @@ use std::{error, fmt};
 
 #[unstable(feature = "proc_macro_diagnostic", issue = "54140")]
 pub use diagnostic::{Diagnostic, Level, MultiSpan};
+#[stable(feature = "proc_macro_lib2", since = "1.86.0")]
+pub use literal_escaper::EscapeError;
 #[unstable(feature = "proc_macro_totokens", issue = "130977")]
 pub use to_tokens::ToTokens;
 
 use crate::escape::{EscapeOptions, escape_bytes};
 
+/// Errors returned when trying to retrieve a literal unescaped value.
+#[stable(feature = "proc_macro_lib2", since = "1.86.0")]
+pub enum ConversionErrorKind {
+    /// The literal failed to be escaped, take a look at [`EscapeError`] for more information.
+    FailedToUnescape(EscapeError),
+    /// Trying to convert a literal with the wrong type.
+    InvalidLiteralKind,
+}
+
 /// Determines whether proc_macro has been made accessible to the currently
 /// running program.
 ///
@@ -1450,6 +1461,106 @@ impl Literal {
             }
         })
     }
+
+    /// Returns the unescaped string value if the current literal is a string or a string literal.
+    #[stable(feature = "proc_macro_lib2", since = "1.86.0")]
+    fn str_value(&self) -> Result<String, ConversionErrorKind> {
+        self.with_symbol_and_suffix(|symbol, suffix| match self.0.kind {
+            bridge::LitKind::Str => {
+                if s.contains('\\') {
+                    let mut buf = String::with_capacity(s.len());
+                    let mut error = None;
+                    // Force-inlining here is aggressive but the closure is
+                    // called on every char in the string, so it can be hot in
+                    // programs with many long strings containing escapes.
+                    unescape_unicode(
+                        s,
+                        Mode::Str,
+                        &mut #[inline(always)]
+                        |_, c| match c {
+                            Ok(c) => buf.push(c),
+                            Err(err) => {
+                                if err.is_fatal() {
+                                    error = Some(ConversionErrorKind::FailedToUnescape);
+                                }
+                            }
+                        },
+                    );
+                    if let Some(error) = error { Err(error) } else { Ok(buf) }
+                } else {
+                    Ok(symbol.to_string())
+                }
+            }
+            bridge::LitKind::StrRaw(_) => Ok(symbol.to_string()),
+            _ => Err(ConversionErrorKind::InvalidLiteralKind),
+        })
+    }
+
+    /// Returns the unescaped string value if the current literal is a c-string or a c-string
+    /// literal.
+    #[stable(feature = "proc_macro_lib2", since = "1.86.0")]
+    fn cstr_value(&self) -> Result<Vec<u8>, ConversionErrorKind> {
+        self.with_symbol_and_suffix(|symbol, suffix| match self.0.kind {
+            bridge::LitKind::CStr => {
+                let s = symbol.as_str();
+                let mut error = None;
+                let mut buf = Vec::with_capacity(s.len());
+                unescape_mixed(s, Mode::CStr, &mut |_span, c| match c {
+                    Ok(MixedUnit::Char(c)) => {
+                        buf.extend_from_slice(c.encode_utf8(&mut [0; 4]).as_bytes())
+                    }
+                    Ok(MixedUnit::HighByte(b)) => buf.push(b),
+                    Err(err) => {
+                        if err.is_fatal() {
+                            error = Some(err);
+                        }
+                    }
+                });
+                if let Some(error) = error {
+                    Err(error)
+                } else {
+                    buf.push(0);
+                    Ok(buf)
+                }
+            }
+            bridge::LitKind::CStrRaw(_) => {
+                // Raw strings have no escapes so we can convert the symbol
+                // directly to a `Lrc<u8>` after appending the terminating NUL
+                // char.
+                let mut buf = symbol.as_str().to_owned().into_bytes();
+                buf.push(0);
+                Ok(buf)
+            }
+            _ => Err(ConversionErrorKind::InvalidLiteralKind),
+        })
+    }
+
+    /// Returns the unescaped string value if the current literal is a byte string or a byte string
+    /// literal.
+    #[stable(feature = "proc_macro_lib2", since = "1.86.0")]
+    fn byte_str_value(&self) -> Result<Vec<u8>, ConversionErrorKind> {
+        self.with_symbol_and_suffix(|symbol, suffix| match self.0.kind {
+            bridge::LitKind::ByteStr => {
+                let mut buf = Vec::with_capacity(s.len());
+
+                unescape_unicode(s, Mode::ByteStr, &mut |_, c| match c {
+                    Ok(c) => buf.push(byte_from_char(c)),
+                    Err(err) => {
+                        if err.is_fatal() {
+                            error = Some(ConversionErrorKind::FailedToUnescape);
+                        }
+                    }
+                });
+                if let Some(error) = error { Err(error) } else { Ok(buf) }
+            }
+            bridge::LitKind::ByteStrRaw(_) => {
+                // Raw strings have no escapes so we can convert the symbol
+                // directly to a `Lrc<u8>`.
+                Ok(symbol.as_str().to_owned().into_bytes())
+            }
+            _ => Err(ConversionErrorKind::InvalidLiteralKind),
+        })
+    }
 }
 
 /// Parse a single literal from its stringified representation.