Deprecate #![crate_type] and #![crate_name]

compiler/rustc_lint/src/builtin.rs

@@ -2961,3 +2961,23 @@ impl<'tcx> LateLintPass<'tcx> for ClashingExternDeclarations {
         }
     }
 }
+
+pub(crate) struct DeprecatedCrateInfoAttrs;
+
+impl_lint_pass!(DeprecatedCrateInfoAttrs => [DEPRECATED_CRATE_INFO_ATTRS]);
+
+impl EarlyLintPass for DeprecatedCrateInfoAttrs {
+    fn check_crate(&mut self, cx: &EarlyContext<'_>, krate: &ast::Crate) {
+        for attr in &krate.attrs {
+            if attr.has_name(sym::crate_type) {
+                cx.struct_span_lint(DEPRECATED_CRATE_INFO_ATTRS, attr.span, |lint| {
+                    lint.build("using deprecated `#![crate_type]` attribute").emit();
+                })
+            } else if attr.has_name(sym::crate_name) {
+                cx.struct_span_lint(DEPRECATED_CRATE_INFO_ATTRS, attr.span, |lint| {
+                    lint.build("using deprecated `#![crate_name]` attribute").emit();
+                })
+            }
+        }
+    }
+}

compiler/rustc_lint/src/lib.rs

@@ -132,6 +132,7 @@ macro_rules! early_lint_passes {
                 IncompleteFeatures: IncompleteFeatures,
                 RedundantSemicolons: RedundantSemicolons,
                 UnusedDocComment: UnusedDocComment,
+                DeprecatedCrateInfoAttrs: DeprecatedCrateInfoAttrs,
             ]
         );
     };

compiler/rustc_lint_defs/src/builtin.rs

@@ -2959,6 +2959,7 @@ declare_lint_pass! {
         DISJOINT_CAPTURE_DROP_REORDER,
         LEGACY_DERIVE_HELPERS,
         PROC_MACRO_BACK_COMPAT,
+        DEPRECATED_CRATE_INFO_ATTRS,
     ]
 }
 
@@ -3136,3 +3137,50 @@ declare_lint! {
         })
     };
 }
+
+declare_lint! {
+    /// The `deprecated_crate_info_attrs` lint detects uses of the `#![crate_type]`
+    /// and `#![crate_name]` attributes to specify the crate type and name in the
+    /// source code.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// #![crate_type = "lib"]
+    /// ```
+    ///
+    /// This will produce:
+    ///
+    /// ```text
+    /// warning: using deprecated `#![crate_type]` attribute
+    ///   ::: $DIR/group-compat-hack.rs:1:5
+    ///    |
+    /// LL |     #![crate_type = "lib"]
+    ///    |     ^^^^^^^^^^^^^^^^^^^^^^
+    ///    |
+    ///    = note: `#[warn(deprecated_crate_info_attrs)]` on by default
+    ///    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+    ///    = note: for more information, see issue #XXXXX <https://github.com/rust-lang/rust/issues/XXXXX>
+    /// ```
+    ///
+    /// ### Explanation
+    ///
+    /// The `#![crate_type]` and `#![crate_name]` attributes require a hack in the
+    /// compiler to be able to change the used crate type and crate name after the
+    /// program has been parsed. Neither attribute works in combination with Cargo
+    /// as it explicitly passes `--crate-type` and `--crate-name` on the commandline,
+    /// which must match to the value used in the source code.
+    ///
+    /// To fix the warning use `--crate-type` on the commandline when running rustc
+    /// instead of `#![crate_type]` and `--crate-name` instead of `#![crate_name]`.
+    pub DEPRECATED_CRATE_INFO_ATTRS,
+    Warn,
+    "detects deprecated usage of #![crate_type] and #![crate_name]",
+    @future_incompatible = FutureIncompatibleInfo {
+        reference: "issue #XXXXX <https://github.com/rust-lang/rust/issues/XXXXX>", // FIXME
+        edition: None,
+        future_breakage: Some(FutureBreakage {
+            date: None
+        })
+    };
+}

library/rtstartup/rsbegin.rs

@@ -15,7 +15,6 @@
 #![feature(no_core)]
 #![feature(lang_items)]
 #![feature(auto_traits)]
-#![crate_type = "rlib"]
 #![no_core]
 #![allow(non_camel_case_types)]
 

library/rtstartup/rsend.rs

@@ -3,7 +3,6 @@
 #![feature(no_core)]
 #![feature(lang_items)]
 #![feature(auto_traits)]
-#![crate_type = "rlib"]
 #![no_core]
 
 #[lang = "sized"]

library/test/src/lib.rs

@@ -17,7 +17,6 @@
 // this crate, which relies on this attribute (rather than the value of `--crate-name` passed by
 // cargo) to detect this crate.
 
-#![crate_name = "test"]
 #![unstable(feature = "test", issue = "50297")]
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/", test(attr(deny(warnings))))]
 #![cfg_attr(unix, feature(libc))]

src/bootstrap/compile.rs

@@ -467,6 +467,8 @@ impl Step for StartupObjects {
                         .arg("--target")
                         .arg(target.rustc_target_arg())
                         .arg("--emit=obj")
+                        .arg("--crate-type")
+                        .arg("rlib")
                         .arg("-o")
                         .arg(dst_file)
                         .arg(src_file),

src/test/ui/attributes/deprecated-crate-info-attrs.rs

@@ -0,0 +1,2 @@
+#![crate_type = "lib"] //~WARN using deprecated `#![crate_type]` attribute
+#![crate_name = "foo"] //~WARN using deprecated `#![crate_name]` attribute

src/tools/compiletest/src/main.rs

@@ -1,4 +1,3 @@
-#![crate_name = "compiletest"]
 // The `test` crate is the only unstable feature
 // allowed here, just to share similar code.
 #![feature(test)]