handle ci-rustc incompatible options during config parse

This change ensures that `config.toml` does not use CI rustc incompatible
options when CI rustc is enabled. This is necessary because some options
can change compiler's behavior in certain scenarios.

The list may not be complete, but should be a good first step as it's better than nothing!

Signed-off-by: onur-ozkan <work@onurozkan.dev>

src/bootstrap/src/core/config/config.rs

@@ -33,7 +33,7 @@ macro_rules! check_ci_llvm {
         assert!(
             $name.is_none(),
             "setting {} is incompatible with download-ci-llvm.",
-            stringify!($name)
+            stringify!($name).replace("_", "-")
         );
     };
 }
@@ -1547,7 +1547,15 @@ impl Config {
         let mut lld_enabled = None;
 
         let mut is_user_configured_rust_channel = false;
+
         if let Some(rust) = toml.rust {
+            config.download_rustc_commit =
+                config.download_ci_rustc_commit(rust.download_rustc.clone());
+
+            if config.download_rustc_commit.is_some() {
+                check_incompatible_options_for_ci_rustc(&rust);
+            }
+
             let Rust {
                 optimize: optimize_toml,
                 debug: debug_toml,
@@ -1595,7 +1603,7 @@ impl Config {
                 new_symbol_mangling,
                 profile_generate,
                 profile_use,
-                download_rustc,
+                download_rustc: _,
                 lto,
                 validate_mir_opts,
                 frame_pointers,
@@ -1605,11 +1613,7 @@ impl Config {
             } = rust;
 
             is_user_configured_rust_channel = channel.is_some();
-            set(&mut config.channel, channel);
-
-            config.download_rustc_commit = config.download_ci_rustc_commit(download_rustc);
-
-            // FIXME: handle download-rustc incompatible options.
+            set(&mut config.channel, channel.clone());
 
             debug = debug_toml;
             debug_assertions = debug_assertions_toml;
@@ -2591,6 +2595,113 @@ impl Config {
     }
 }
 
+/// Checks the CI rustc incompatible options by destructuring the `Rust` instance
+/// and makes sure that no rust options from config.toml are missed.
+fn check_incompatible_options_for_ci_rustc(rust: &Rust) {
+    macro_rules! err {
+        ($name:expr) => {
+            assert!(
+                $name.is_none(),
+                "ERROR: Setting `rust.{}` is incompatible with `rust.download-rustc`.",
+                stringify!($name).replace("_", "-")
+            );
+        };
+    }
+
+    macro_rules! warn {
+        ($name:expr) => {
+            if $name.is_some() {
+                println!(
+                    "WARNING: `rust.{}` has no effect with `rust.download-rustc`.",
+                    stringify!($name).replace("_", "-")
+                );
+            }
+        };
+    }
+
+    let Rust {
+        // Following options are the CI rustc incompatible ones.
+        optimize,
+        debug_logging,
+        debuginfo_level_rustc,
+        llvm_tools,
+        llvm_bitcode_linker,
+        lto,
+        stack_protector,
+        strip,
+        lld_mode,
+        jemalloc,
+        rpath,
+        channel,
+        description,
+        incremental,
+        default_linker,
+
+        // Rest of the options can simply be ignored.
+        debug: _,
+        codegen_units: _,
+        codegen_units_std: _,
+        debug_assertions: _,
+        debug_assertions_std: _,
+        overflow_checks: _,
+        overflow_checks_std: _,
+        debuginfo_level: _,
+        debuginfo_level_std: _,
+        debuginfo_level_tools: _,
+        debuginfo_level_tests: _,
+        split_debuginfo: _,
+        backtrace: _,
+        parallel_compiler: _,
+        musl_root: _,
+        verbose_tests: _,
+        optimize_tests: _,
+        codegen_tests: _,
+        omit_git_hash: _,
+        dist_src: _,
+        save_toolstates: _,
+        codegen_backends: _,
+        lld: _,
+        deny_warnings: _,
+        backtrace_on_ice: _,
+        verify_llvm_ir: _,
+        thin_lto_import_instr_limit: _,
+        remap_debuginfo: _,
+        test_compare_mode: _,
+        llvm_libunwind: _,
+        control_flow_guard: _,
+        ehcont_guard: _,
+        new_symbol_mangling: _,
+        profile_generate: _,
+        profile_use: _,
+        download_rustc: _,
+        validate_mir_opts: _,
+        frame_pointers: _,
+    } = rust;
+
+    // There are two kinds of checks for CI rustc incompatible options:
+    //    1. Checking an option that may change the compiler behaviour/output.
+    //    2. Checking an option that have no effect on the compiler behaviour/output.
+    //
+    // If the option belongs to the first category, we call `err` macro for a hard error;
+    // otherwise, we just print a warning with `warn` macro.
+    err!(optimize);
+    err!(debug_logging);
+    err!(debuginfo_level_rustc);
+    err!(default_linker);
+    err!(rpath);
+    err!(strip);
+    err!(stack_protector);
+    err!(lld_mode);
+    err!(llvm_tools);
+    err!(llvm_bitcode_linker);
+    err!(jemalloc);
+    err!(lto);
+
+    warn!(channel);
+    warn!(description);
+    warn!(incremental);
+}
+
 fn set<T>(field: &mut T, val: Option<T>) {
     if let Some(v) = val {
         *field = v;