Report an error on incompatible symbol definitions

src/abi/mod.rs

@@ -4,6 +4,7 @@
 mod pass_mode;
 mod returning;
 
+use cranelift_module::ModuleError;
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use rustc_middle::ty::layout::FnAbiOf;
 use rustc_target::abi::call::{Conv, FnAbi};
@@ -69,7 +70,17 @@ pub(crate) fn import_function<'tcx>(
 ) -> FuncId {
     let name = tcx.symbol_name(inst).name;
     let sig = get_function_sig(tcx, module.isa().triple(), inst);
-    module.declare_function(name, Linkage::Import, &sig).unwrap()
+    match module.declare_function(name, Linkage::Import, &sig) {
+        Ok(func_id) => func_id,
+        Err(ModuleError::IncompatibleDeclaration(_)) => tcx.sess.fatal(&format!(
+            "attempt to declare `{name}` as function, but it was already declared as static"
+        )),
+        Err(ModuleError::IncompatibleSignature(_, prev_sig, new_sig)) => tcx.sess.fatal(&format!(
+            "attempt to declare `{name}` with signature {new_sig:?}, \
+             but it was already declared with signature {prev_sig:?}"
+        )),
+        Err(err) => Err::<_, _>(err).unwrap(),
+    }
 }
 
 impl<'tcx> FunctionCx<'_, '_, 'tcx> {

src/constant.rs

@@ -316,14 +316,18 @@ fn data_id_for_static(
 
     let attrs = tcx.codegen_fn_attrs(def_id);
 
-    let data_id = module
-        .declare_data(
-            &*symbol_name,
-            linkage,
-            is_mutable,
-            attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL),
-        )
-        .unwrap();
+    let data_id = match module.declare_data(
+        &*symbol_name,
+        linkage,
+        is_mutable,
+        attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL),
+    ) {
+        Ok(data_id) => data_id,
+        Err(ModuleError::IncompatibleDeclaration(_)) => tcx.sess.fatal(&format!(
+            "attempt to declare `{symbol_name}` as static, but it was already declared as function"
+        )),
+        Err(err) => Err::<_, _>(err).unwrap(),
+    };
 
     if rlinkage.is_some() {
         // Comment copied from https://github.com/rust-lang/rust/blob/45060c2a66dfd667f88bd8b94261b28a58d85bd5/src/librustc_codegen_llvm/consts.rs#L141