feat: Warn that edition 2015 code is not explicitly supported

Author: zalanlevai

mutest-driver/src/passes/analysis.rs

@@ -4,6 +4,7 @@ use rustc_hash::FxHashSet;
 use rustc_interface::{create_and_enter_global_ctxt, passes, run_compiler};
 use rustc_interface::interface::Result as CompilerResult;
 use rustc_span::ErrorGuaranteed;
+use rustc_span::edition::Edition;
 use rustc_span::fatal_error::FatalError;
 use mutest_emit::codegen::symbols::span_diagnostic_ord;
 
@@ -67,6 +68,12 @@ pub fn run(config: &mut Config) -> CompilerResult<Option<AnalysisPassResult>> {
         //       relevant attribute validation is performed during macro expansion.
         mutest_emit::codegen::tool_attr::register(sess, &mut crate_ast);
 
+        if sess.edition() == Edition::Edition2015 {
+            let mut diagnostic = sess.dcx().struct_warn("edition 2015 code is not explicitly supported");
+            diagnostic.note("you may encounter issues with generated code from macro expansion sanitization and mutation operators");
+            diagnostic.emit();
+        }
+
         let result = create_and_enter_global_ctxt(compiler, crate_ast.clone(), |tcx| -> Flow<AnalysisPassResult, ErrorGuaranteed> {
             let (mut generated_crate_ast, def_res) = {
                 let (resolver, expanded_crate_ast) = &*tcx.resolver_for_lowering().borrow();

tests/ui/warn_on_edition_2015.rs

@@ -0,0 +1,14 @@
+//@ print-mutants
+//@ build
+//@ stdout
+//@ stderr
+//@ edition: 2015
+
+fn mutated_fn(a: i32, b: i32) -> i32 {
+    a + b
+}
+
+#[test]
+fn test() {
+    assert_eq!(11, mutated_fn(5, 6));
+}

tests/ui/warn_on_edition_2015.stderr

@@ -0,0 +1,6 @@
+warning: edition 2015 code is not explicitly supported
+  |
+  = note: you may encounter issues with generated code from macro expansion sanitization and mutation operators
+
+warning: 1 warning emitted
+

tests/ui/warn_on_edition_2015.stdout

@@ -0,0 +1,17 @@
+1 mutation
+  - [arg_default_shadow] ignore `a` argument by shadowing it with `Default::default()` in mutated_fn at tests/ui/warn_on_edition_2015.rs:7:15: 7:21
+    <-(0)- test
+
+1 mutation
+  - [arg_default_shadow] ignore `b` argument by shadowing it with `Default::default()` in mutated_fn at tests/ui/warn_on_edition_2015.rs:7:23: 7:29
+    <-(0)- test
+
+1 mutation
+  - [math_op_add_sub_swap] swap operator `+` for `-` in mutated_fn at tests/ui/warn_on_edition_2015.rs:8:5: 8:10
+    <-(0)- test
+
+1 mutation
+  - [math_op_add_mul_swap] swap operator `+` for `*` in mutated_fn at tests/ui/warn_on_edition_2015.rs:8:5: 8:10
+    <-(0)- test
+
+4 mutants; 4 mutations; 4 safe; 0 unsafe (0 tainted); 0 batched; 4 unbatched