Add wasm_c_abi future-incompat lint

Author: daxpedda

compiler/rustc_lint_defs/src/builtin.rs

@@ -131,6 +131,7 @@ declare_lint_pass! {
         UNUSED_VARIABLES,
         USELESS_DEPRECATED,
         WARNINGS,
+        WASM_C_ABI,
         WHERE_CLAUSES_OBJECT_SAFETY,
         WRITES_THROUGH_IMMUTABLE_POINTER,
         // tidy-alphabetical-end
@@ -4656,3 +4657,41 @@ declare_lint! {
         reference: "issue #X <https://github.com/rust-lang/rust/issues/X>",
     };
 }
+
+declare_lint! {
+    /// The `wasm_c_abi` lint detects crate dependencies that are incompatible
+    /// with future versions of Rust that will emit spec-compliant C ABI.
+    ///
+    /// ### Example
+    ///
+    /// ```rust,ignore (needs extern crate)
+    /// #![deny(wasm_c_abi)]
+    /// ```
+    ///
+    /// This will produce:
+    ///
+    /// ```text
+    /// error: the following packages contain code that will be rejected by a future version of Rust: wasm-bindgen v0.2.87
+    ///   |
+    /// note: the lint level is defined here
+    ///  --> src/lib.rs:1:9
+    ///   |
+    /// 1 | #![deny(wasm_c_abi)]
+    ///   |         ^^^^^^^^^^
+    /// ```
+    ///
+    /// ### Explanation
+    ///
+    /// Rust has historically emitted non-spec-compliant C ABI. This has caused
+    /// incompatibilities between other compilers and Wasm targets. In a future
+    /// version of Rust this will be fixed and therefor dependencies relying on
+    /// the non-spec-compliant C ABI will stop functioning.
+    pub WASM_C_ABI,
+    Warn,
+    "detects dependencies that are incompatible with the Wasm C ABI",
+    @future_incompatible = FutureIncompatibleInfo {
+        reason: FutureIncompatibilityReason::FutureReleaseErrorReportInDeps,
+        reference: "issue #71871 <https://github.com/rust-lang/rust/issues/71871>",
+    };
+    crate_level_only
+}

compiler/rustc_metadata/src/creader.rs

@@ -30,8 +30,9 @@ use proc_macro::bridge::client::ProcMacro;
 use std::error::Error;
 use std::ops::Fn;
 use std::path::Path;
+use std::str::FromStr;
 use std::time::Duration;
-use std::{cmp, iter};
+use std::{cmp, env, iter};
 
 /// The backend's way to give the crate store access to the metadata in a library.
 /// Note that it returns the raw metadata bytes stored in the library file, whether
@@ -989,13 +990,53 @@ impl<'a, 'tcx> CrateLoader<'a, 'tcx> {
         }
     }
 
+    fn report_future_incompatible_deps(&self, krate: &ast::Crate) {
+        let name = self.tcx.crate_name(LOCAL_CRATE);
+
+        if name.as_str() == "wasm_bindgen" {
+            if !env::var("CARGO_PKG_VERSION_MAJOR")
+                .ok()
+                .and_then(|major| u64::from_str(&major).ok())
+                .is_some_and(|major| major == 0)
+            {
+                return;
+            }
+            if !env::var("CARGO_PKG_VERSION_MINOR")
+                .ok()
+                .and_then(|minor| u64::from_str(&minor).ok())
+                .is_some_and(|minor| minor <= 2)
+            {
+                return;
+            }
+            if !env::var("CARGO_PKG_VERSION_PATCH")
+                .ok()
+                .and_then(|patch| u64::from_str(&patch).ok())
+                .is_some_and(|minor| minor <= 87)
+            {
+                return;
+            }
+
+            // Make a point span rather than covering the whole file
+            let span = krate.spans.inner_span.shrink_to_lo();
+
+            self.sess.parse_sess.buffer_lint(
+                lint::builtin::WASM_C_ABI,
+                span,
+                ast::CRATE_NODE_ID,
+                "older versions of the `wasm-bindgen` crate will be incompatible with future versions of Rust; \
+                please update to `wasm-bindgen` v0.2.88".to_string(),
+            );
+        }
+    }
+
     pub fn postprocess(&mut self, krate: &ast::Crate) {
         self.inject_forced_externs();
         self.inject_profiler_runtime(krate);
         self.inject_allocator_crate(krate);
         self.inject_panic_runtime(krate);
 
         self.report_unused_deps(krate);
+        self.report_future_incompatible_deps(krate);
 
         info!("{:?}", CrateDump(self.cstore));
     }