refactor(lints): Restrict new Manifest::rustflags to being lint_rustflags

This will avoid people reusing it in the future and expanding its use
without updating fingerprinting/metadata.

Author: epage

src/cargo/core/compiler/fingerprint/mod.rs

@@ -87,7 +87,7 @@
 //! [^5]: Config settings that are not otherwise captured anywhere else.
 //!       Currently, this is only `doc.extern-map`.
 //!
-//! [^6]: Via [`Manifest::rustflags`][crate::core::Manifest::rustflags]
+//! [^6]: Via [`Manifest::lint_rustflags`][crate::core::Manifest::lint_rustflags]
 //!
 //! When deciding what should go in the Metadata vs the Fingerprint, consider
 //! that some files (like dylibs) do not have a hash in their filename. Thus,
@@ -1417,7 +1417,7 @@ fn calculate_normal(cx: &mut Context<'_, '_>, unit: &Unit) -> CargoResult<Finger
         unit.mode,
         cx.bcx.extra_args_for(unit),
         cx.lto[unit],
-        unit.pkg.manifest().rustflags(),
+        unit.pkg.manifest().lint_rustflags(),
     ));
     // Include metadata since it is exposed as environment variables.
     let m = unit.pkg.manifest().metadata();

src/cargo/core/compiler/mod.rs

@@ -762,7 +762,7 @@ fn rustdoc(cx: &mut Context<'_, '_>, unit: &Unit) -> CargoResult<Work> {
     add_error_format_and_color(cx, &mut rustdoc);
     add_allow_features(cx, &mut rustdoc);
 
-    rustdoc.args(unit.pkg.manifest().rustflags());
+    rustdoc.args(unit.pkg.manifest().lint_rustflags());
     if let Some(args) = cx.bcx.extra_args_for(unit) {
         rustdoc.args(args);
     }
@@ -1075,7 +1075,7 @@ fn build_base_args(
         cmd.arg("-C").arg(format!("debuginfo={}", debuginfo));
     }
 
-    cmd.args(unit.pkg.manifest().rustflags());
+    cmd.args(unit.pkg.manifest().lint_rustflags());
     if !rustflags.is_empty() {
         cmd.args(&rustflags);
     }

src/cargo/core/manifest.rs

@@ -63,7 +63,7 @@ pub struct Manifest {
     default_run: Option<String>,
     metabuild: Option<Vec<String>>,
     resolve_behavior: Option<ResolveBehavior>,
-    rustflags: Vec<String>,
+    lint_rustflags: Vec<String>,
 }
 
 /// When parsing `Cargo.toml`, some warnings should silenced
@@ -406,7 +406,7 @@ impl Manifest {
         original: Rc<TomlManifest>,
         metabuild: Option<Vec<String>>,
         resolve_behavior: Option<ResolveBehavior>,
-        rustflags: Vec<String>,
+        lint_rustflags: Vec<String>,
     ) -> Manifest {
         Manifest {
             summary,
@@ -432,7 +432,7 @@ impl Manifest {
             default_run,
             metabuild,
             resolve_behavior,
-            rustflags,
+            lint_rustflags,
         }
     }
 
@@ -517,9 +517,9 @@ impl Manifest {
         self.resolve_behavior
     }
 
-    /// Package-wide RUSTFLAGS
-    pub fn rustflags(&self) -> &[String] {
-        self.rustflags.as_slice()
+    /// `RUSTFLAGS` from the `[lints]` table
+    pub fn lint_rustflags(&self) -> &[String] {
+        self.lint_rustflags.as_slice()
     }
 
     pub fn map_source(self, to_replace: SourceId, replace_with: SourceId) -> Manifest {