Make the wasm_c_abi future compat warning a hard error

This is the next step in getting rid of the broken C abi for
wasm32-unknown-unknown.

compiler/rustc_lint/messages.ftl

@@ -974,6 +974,3 @@ lint_use_let_underscore_ignore_suggestion = use `let _ = ...` to ignore the expr
 
 lint_variant_size_differences =
     enum variant is more than three times larger ({$largest} bytes) than the next largest
-
-lint_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_lint/src/early/diagnostics.rs

@@ -430,7 +430,6 @@ pub(super) fn decorate_lint(
         BuiltinLintDiag::UnusedCrateDependency { extern_crate, local_crate } => {
             lints::UnusedCrateDependency { extern_crate, local_crate }.decorate_lint(diag)
         }
-        BuiltinLintDiag::WasmCAbi => lints::WasmCAbi.decorate_lint(diag),
         BuiltinLintDiag::IllFormedAttributeInput { suggestions } => {
             lints::IllFormedAttributeInput {
                 num_suggestions: suggestions.len(),

compiler/rustc_lint/src/lints.rs

@@ -2561,10 +2561,6 @@ pub(crate) struct UnusedCrateDependency {
     pub local_crate: Symbol,
 }
 
-#[derive(LintDiagnostic)]
-#[diag(lint_wasm_c_abi)]
-pub(crate) struct WasmCAbi;
-
 #[derive(LintDiagnostic)]
 #[diag(lint_ill_formed_attribute_input)]
 pub(crate) struct IllFormedAttributeInput {

compiler/rustc_lint_defs/src/builtin.rs

@@ -143,7 +143,6 @@ declare_lint_pass! {
         UNUSED_VARIABLES,
         USELESS_DEPRECATED,
         WARNINGS,
-        WASM_C_ABI,
         // tidy-alphabetical-end
     ]
 }
@@ -4647,44 +4646,6 @@ declare_lint! {
     };
 }
 
-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,
-    Deny,
-    "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
-}
-
 declare_lint! {
     /// The `uncovered_param_in_projection` lint detects a violation of one of Rust's orphan rules for
     /// foreign trait implementations that concerns the use of type parameters inside trait associated

compiler/rustc_lint_defs/src/lib.rs

@@ -783,7 +783,6 @@ pub enum BuiltinLintDiag {
         extern_crate: Symbol,
         local_crate: Symbol,
     },
-    WasmCAbi,
     IllFormedAttributeInput {
         suggestions: Vec<String>,
     },

compiler/rustc_metadata/messages.ftl

@@ -290,6 +290,9 @@ metadata_unsupported_abi =
 metadata_unsupported_abi_i686 =
     ABI not supported by `#[link(kind = "raw-dylib")]` on i686
 
+metadata_wasm_c_abi =
+    older versions of the `wasm-bindgen` crate are incompatible with current versions of Rust; please update to `wasm-bindgen` v0.2.88
+
 metadata_wasm_import_form =
     wasm import module must be of the form `wasm_import_module = "string"`
 

compiler/rustc_metadata/src/creader.rs

@@ -1076,12 +1076,7 @@ impl<'a, 'tcx> CrateLoader<'a, 'tcx> {
             // 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,
-                BuiltinLintDiag::WasmCAbi,
-            );
+            self.sess.dcx().emit_err(errors::WasmCAbi { span });
         }
     }
 

compiler/rustc_metadata/src/errors.rs

@@ -732,3 +732,10 @@ pub struct ImportNameTypeRaw {
     #[primary_span]
     pub span: Span,
 }
+
+#[derive(Diagnostic)]
+#[diag(metadata_wasm_c_abi)]
+pub(crate) struct WasmCAbi {
+    #[primary_span]
+    pub span: Span,
+}