Auto merge of #14302 - weihanglo:check-cfg, r=epage

fix: remove rustc probe for `--check-cfg` support

### What does this PR try to resolve?

This is a follow-up to #13571 as now everything for `-Z check-cfg` is stabilized.

### How should we test and review this PR?

Existing test suite passes.

### Additional information

Author: bors

src/cargo/core/compiler/build_context/target_info.rs

@@ -54,11 +54,6 @@ pub struct TargetInfo {
     pub rustflags: Rc<[String]>,
     /// Extra flags to pass to `rustdoc`, see [`extra_args`].
     pub rustdocflags: Rc<[String]>,
-    /// Whether or not rustc (stably) supports the `--check-cfg` flag.
-    ///
-    /// Can be removed once the minimum supported rustc version of Cargo is
-    /// at minimum 1.80.0.
-    pub support_check_cfg: bool,
 }
 
 /// Kind of each file generated by a Unit, part of `FileType`.
@@ -204,13 +199,6 @@ impl TargetInfo {
                 process.arg("--crate-type").arg(crate_type.as_str());
             }
 
-            let support_check_cfg = rustc
-                .cached_output(
-                    process.clone().arg("--check-cfg").arg("cfg()"),
-                    extra_fingerprint,
-                )
-                .is_ok();
-
             process.arg("--print=sysroot");
             process.arg("--print=split-debuginfo");
             process.arg("--print=crate-name"); // `___` as a delimiter.
@@ -323,7 +311,6 @@ impl TargetInfo {
                 .into(),
                 cfg,
                 support_split_debuginfo,
-                support_check_cfg,
             });
         }
     }

src/cargo/core/compiler/build_runner/mod.rs

@@ -246,7 +246,7 @@ impl<'a, 'gctx> BuildRunner<'a, 'gctx> {
                 let mut args = compiler::extern_args(&self, unit, &mut unstable_opts)?;
                 args.extend(compiler::lto_args(&self, unit));
                 args.extend(compiler::features_args(unit));
-                args.extend(compiler::check_cfg_args(&self, unit)?);
+                args.extend(compiler::check_cfg_args(unit)?);
 
                 let script_meta = self.find_build_script_metadata(unit);
                 if let Some(meta) = script_meta {

src/cargo/core/compiler/custom_build.rs

@@ -405,11 +405,6 @@ fn build_work(build_runner: &mut BuildRunner<'_, '_>, unit: &Unit) -> CargoResul
     paths::create_dir_all(&script_out_dir)?;
 
     let nightly_features_allowed = build_runner.bcx.gctx.nightly_features_allowed;
-    let extra_check_cfg = build_runner
-        .bcx
-        .target_data
-        .info(unit.kind)
-        .support_check_cfg;
     let targets: Vec<Target> = unit.pkg.targets().to_vec();
     let msrv = unit.pkg.rust_version().cloned();
     // Need a separate copy for the fresh closure.
@@ -557,7 +552,6 @@ fn build_work(build_runner: &mut BuildRunner<'_, '_>, unit: &Unit) -> CargoResul
             &pkg_descr,
             &script_out_dir,
             &script_out_dir,
-            extra_check_cfg,
             nightly_features_allowed,
             &targets,
             &msrv,
@@ -586,7 +580,6 @@ fn build_work(build_runner: &mut BuildRunner<'_, '_>, unit: &Unit) -> CargoResul
                 &pkg_descr,
                 &prev_script_out_dir,
                 &script_out_dir,
-                extra_check_cfg,
                 nightly_features_allowed,
                 &targets_fresh,
                 &msrv_fresh,
@@ -643,7 +636,6 @@ impl BuildOutput {
         pkg_descr: &str,
         script_out_dir_when_generated: &Path,
         script_out_dir: &Path,
-        extra_check_cfg: bool,
         nightly_features_allowed: bool,
         targets: &[Target],
         msrv: &Option<RustVersion>,
@@ -655,7 +647,6 @@ impl BuildOutput {
             pkg_descr,
             script_out_dir_when_generated,
             script_out_dir,
-            extra_check_cfg,
             nightly_features_allowed,
             targets,
             msrv,
@@ -666,15 +657,13 @@ impl BuildOutput {
     ///
     /// * `pkg_descr` --- for error messages
     /// * `library_name` --- for determining if `RUSTC_BOOTSTRAP` should be allowed
-    /// * `extra_check_cfg` --- for `--check-cfg` (if supported)
     pub fn parse(
         input: &[u8],
         // Takes String instead of InternedString so passing `unit.pkg.name()` will give a compile error.
         library_name: Option<String>,
         pkg_descr: &str,
         script_out_dir_when_generated: &Path,
         script_out_dir: &Path,
-        extra_check_cfg: bool,
         nightly_features_allowed: bool,
         targets: &[Target],
         msrv: &Option<RustVersion>,
@@ -921,14 +910,7 @@ impl BuildOutput {
                     linker_args.push((LinkArgTarget::All, value));
                 }
                 "rustc-cfg" => cfgs.push(value.to_string()),
-                "rustc-check-cfg" => {
-                    if extra_check_cfg {
-                        check_cfgs.push(value.to_string());
-                    } else {
-                        // silently ignoring the instruction because the rustc version
-                        // we are using does not support --check-cfg stably
-                    }
-                }
+                "rustc-check-cfg" => check_cfgs.push(value.to_string()),
                 "rustc-env" => {
                     let (key, val) = BuildOutput::parse_rustc_env(&value, &whence)?;
                     // Build scripts aren't allowed to set RUSTC_BOOTSTRAP.
@@ -1265,11 +1247,6 @@ fn prev_build_output(
             &unit.pkg.to_string(),
             &prev_script_out_dir,
             &script_out_dir,
-            build_runner
-                .bcx
-                .target_data
-                .info(unit.kind)
-                .support_check_cfg,
             build_runner.bcx.gctx.nightly_features_allowed,
             unit.pkg.targets(),
             &unit.pkg.rust_version().cloned(),

src/cargo/core/compiler/mod.rs

@@ -732,7 +732,7 @@ fn prepare_rustdoc(build_runner: &BuildRunner<'_, '_>, unit: &Unit) -> CargoResu
     let doc_dir = build_runner.files().out_dir(unit);
     rustdoc.arg("-o").arg(&doc_dir);
     rustdoc.args(&features_args(unit));
-    rustdoc.args(&check_cfg_args(build_runner, unit)?);
+    rustdoc.args(&check_cfg_args(unit)?);
 
     add_error_format_and_color(build_runner, &mut rustdoc);
     add_allow_features(build_runner, &mut rustdoc);
@@ -1125,7 +1125,7 @@ fn build_base_args(
     }
 
     cmd.args(&features_args(unit));
-    cmd.args(&check_cfg_args(build_runner, unit)?);
+    cmd.args(&check_cfg_args(unit)?);
 
     let meta = build_runner.files().metadata(unit);
     cmd.arg("-C").arg(&format!("metadata={}", meta));
@@ -1310,83 +1310,76 @@ fn trim_paths_args(
 }
 
 /// Generates the `--check-cfg` arguments for the `unit`.
-fn check_cfg_args(build_runner: &BuildRunner<'_, '_>, unit: &Unit) -> CargoResult<Vec<OsString>> {
-    if build_runner
-        .bcx
-        .target_data
-        .info(unit.kind)
-        .support_check_cfg
-    {
-        // The routine below generates the --check-cfg arguments. Our goals here are to
-        // enable the checking of conditionals and pass the list of declared features.
-        //
-        // In the simplified case, it would resemble something like this:
-        //
-        //   --check-cfg=cfg() --check-cfg=cfg(feature, values(...))
-        //
-        // but having `cfg()` is redundant with the second argument (as well-known names
-        // and values are implicitly enabled when one or more `--check-cfg` argument is
-        // passed) so we don't emit it and just pass:
-        //
-        //   --check-cfg=cfg(feature, values(...))
-        //
-        // This way, even if there are no declared features, the config `feature` will
-        // still be expected, meaning users would get "unexpected value" instead of name.
-        // This wasn't always the case, see rust-lang#119930 for some details.
+fn check_cfg_args(unit: &Unit) -> CargoResult<Vec<OsString>> {
+    // The routine below generates the --check-cfg arguments. Our goals here are to
+    // enable the checking of conditionals and pass the list of declared features.
+    //
+    // In the simplified case, it would resemble something like this:
+    //
+    //   --check-cfg=cfg() --check-cfg=cfg(feature, values(...))
+    //
+    // but having `cfg()` is redundant with the second argument (as well-known names
+    // and values are implicitly enabled when one or more `--check-cfg` argument is
+    // passed) so we don't emit it and just pass:
+    //
+    //   --check-cfg=cfg(feature, values(...))
+    //
+    // This way, even if there are no declared features, the config `feature` will
+    // still be expected, meaning users would get "unexpected value" instead of name.
+    // This wasn't always the case, see rust-lang#119930 for some details.
 
-        let gross_cap_estimation = unit.pkg.summary().features().len() * 7 + 25;
-        let mut arg_feature = OsString::with_capacity(gross_cap_estimation);
+    let gross_cap_estimation = unit.pkg.summary().features().len() * 7 + 25;
+    let mut arg_feature = OsString::with_capacity(gross_cap_estimation);
 
-        arg_feature.push("cfg(feature, values(");
-        for (i, feature) in unit.pkg.summary().features().keys().enumerate() {
-            if i != 0 {
-                arg_feature.push(", ");
-            }
-            arg_feature.push("\"");
-            arg_feature.push(feature);
-            arg_feature.push("\"");
+    arg_feature.push("cfg(feature, values(");
+    for (i, feature) in unit.pkg.summary().features().keys().enumerate() {
+        if i != 0 {
+            arg_feature.push(", ");
         }
-        arg_feature.push("))");
-
-        // We also include the `docsrs` cfg from the docs.rs service. We include it here
-        // (in Cargo) instead of rustc, since there is a much closer relationship between
-        // Cargo and docs.rs than rustc and docs.rs. In particular, all users of docs.rs use
-        // Cargo, but not all users of rustc (like Rust-for-Linux) use docs.rs.
-
-        let mut args = vec![
-            OsString::from("--check-cfg"),
-            OsString::from("cfg(docsrs)"),
-            OsString::from("--check-cfg"),
-            arg_feature,
-        ];
-
-        // Also include the custom arguments specified in `[lints.rust.unexpected_cfgs.check_cfg]`
-        if let Ok(Some(lints)) = unit.pkg.manifest().resolved_toml().resolved_lints() {
-            if let Some(rust_lints) = lints.get("rust") {
-                if let Some(unexpected_cfgs) = rust_lints.get("unexpected_cfgs") {
-                    if let Some(config) = unexpected_cfgs.config() {
-                        if let Some(check_cfg) = config.get("check-cfg") {
-                            if let Ok(check_cfgs) =
-                                toml::Value::try_into::<Vec<String>>(check_cfg.clone())
-                            {
-                                for check_cfg in check_cfgs {
-                                    args.push(OsString::from("--check-cfg"));
-                                    args.push(OsString::from(check_cfg));
-                                }
-                            // error about `check-cfg` not being a list-of-string
-                            } else {
-                                bail!("`lints.rust.unexpected_cfgs.check-cfg` must be a list of string");
+        arg_feature.push("\"");
+        arg_feature.push(feature);
+        arg_feature.push("\"");
+    }
+    arg_feature.push("))");
+
+    // We also include the `docsrs` cfg from the docs.rs service. We include it here
+    // (in Cargo) instead of rustc, since there is a much closer relationship between
+    // Cargo and docs.rs than rustc and docs.rs. In particular, all users of docs.rs use
+    // Cargo, but not all users of rustc (like Rust-for-Linux) use docs.rs.
+
+    let mut args = vec![
+        OsString::from("--check-cfg"),
+        OsString::from("cfg(docsrs)"),
+        OsString::from("--check-cfg"),
+        arg_feature,
+    ];
+
+    // Also include the custom arguments specified in `[lints.rust.unexpected_cfgs.check_cfg]`
+    if let Ok(Some(lints)) = unit.pkg.manifest().resolved_toml().resolved_lints() {
+        if let Some(rust_lints) = lints.get("rust") {
+            if let Some(unexpected_cfgs) = rust_lints.get("unexpected_cfgs") {
+                if let Some(config) = unexpected_cfgs.config() {
+                    if let Some(check_cfg) = config.get("check-cfg") {
+                        if let Ok(check_cfgs) =
+                            toml::Value::try_into::<Vec<String>>(check_cfg.clone())
+                        {
+                            for check_cfg in check_cfgs {
+                                args.push(OsString::from("--check-cfg"));
+                                args.push(OsString::from(check_cfg));
                             }
+                        // error about `check-cfg` not being a list-of-string
+                        } else {
+                            bail!(
+                                "`lints.rust.unexpected_cfgs.check-cfg` must be a list of string"
+                            );
                         }
                     }
                 }
             }
         }
-
-        Ok(args)
-    } else {
-        Ok(Vec::new())
     }
+
+    Ok(args)
 }
 
 /// Adds LTO related codegen flags.