Add wasm_c_abi future-incompat lint

compiler/rustc_lint_defs/src/builtin.rs

@@ -130,6 +130,7 @@ declare_lint_pass! {
         UNUSED_VARIABLES,
         USELESS_DEPRECATED,
         WARNINGS,
+        WASM_C_ABI,
         WHERE_CLAUSES_OBJECT_SAFETY,
         WRITES_THROUGH_IMMUTABLE_POINTER,
         // tidy-alphabetical-end
@@ -4564,3 +4565,41 @@ declare_lint! {
         reference: "issue #120192 <https://github.com/rust-lang/rust/issues/120192>",
     };
 }
+
+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 therefore 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/messages.ftl

@@ -286,3 +286,6 @@ metadata_wasm_import_form =
 
 metadata_whole_archive_needs_static =
     linking modifier `whole-archive` is only compatible with `static` linking kind
+
+metadata_wasm_c_abi =
+    older versions of the `wasm-bindgen` crate will be incompatible with future versions of Rust; please update to `wasm-bindgen` v0.2.88

compiler/rustc_metadata/src/creader.rs

@@ -31,8 +31,9 @@ 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
@@ -985,13 +986,52 @@ 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" {
+            let major = env::var("CARGO_PKG_VERSION_MAJOR")
+                .ok()
+                .and_then(|major| u64::from_str(&major).ok());
+            let minor = env::var("CARGO_PKG_VERSION_MINOR")
+                .ok()
+                .and_then(|minor| u64::from_str(&minor).ok());
+            let patch = env::var("CARGO_PKG_VERSION_PATCH")
+                .ok()
+                .and_then(|patch| u64::from_str(&patch).ok());
+
+            match (major, minor, patch) {
+                // v1 or bigger is valid.
+                (Some(1..), _, _) => return,
+                // v0.3 or bigger is valid.
+                (Some(0), Some(3..), _) => return,
+                // v0.2.88 or bigger is valid.
+                (Some(0), Some(2), Some(88..)) => return,
+                // Not using Cargo.
+                (None, None, None) => return,
+                _ => (),
+            }
+
+            // Make a point span rather than covering the whole file
+            let span = krate.spans.inner_span.shrink_to_lo();
+
+            self.sess.psess.buffer_lint(
+                lint::builtin::WASM_C_ABI,
+                span,
+                ast::CRATE_NODE_ID,
+                errors::WasmCAbi,
+            );
+        }
+    }
+
     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));
     }

compiler/rustc_metadata/src/errors.rs

@@ -726,3 +726,7 @@ pub struct ImportNameTypeRaw {
     #[primary_span]
     pub span: Span,
 }
+
+#[derive(Diagnostic)]
+#[diag(metadata_wasm_c_abi)]
+pub struct WasmCAbi;