Remove current implementation of `./x suggest`

This is quite a bit of implementation complexity, yet it is quite
broken, and we don't have the maintenance bandwidth to address.

Remove the current implementation if only to reduce bootstrap's
implementation complexity; the `suggest` flow comes with its own set of
hacks.

20 files changed, 10 insertions, 348 deletions

diff --git a/Cargo.lock b/Cargo.lock
index a6c36b4bdfa..ff2b21c64b0 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -5189,14 +5189,6 @@ dependencies = [
 ]
 
 [[package]]
-name = "suggest-tests"
-version = "0.1.0"
-dependencies = [
- "build_helper",
- "glob",
-]
-
-[[package]]
 name = "syn"
 version = "1.0.109"
 source = "registry+https://github.com/rust-lang/crates.io-index"
diff --git a/Cargo.toml b/Cargo.toml
index 6d3425f4115..67c7a9d67ed 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -39,7 +39,6 @@ members = [
   "src/tools/rustdoc-gui-test",
   "src/tools/rustdoc-themes",
   "src/tools/rustfmt",
-  "src/tools/suggest-tests",
   "src/tools/test-float-parse",
   "src/tools/tidy",
   "src/tools/tier-check",
diff --git a/src/bootstrap/src/core/build_steps/mod.rs b/src/bootstrap/src/core/build_steps/mod.rs
index fcb6abea434..c2ad9a4df59 100644
--- a/src/bootstrap/src/core/build_steps/mod.rs
+++ b/src/bootstrap/src/core/build_steps/mod.rs
@@ -11,7 +11,6 @@ pub(crate) mod llvm;
 pub(crate) mod perf;
 pub(crate) mod run;
 pub(crate) mod setup;
-pub(crate) mod suggest;
 pub(crate) mod synthetic_targets;
 pub(crate) mod test;
 pub(crate) mod tool;
diff --git a/src/bootstrap/src/core/build_steps/suggest.rs b/src/bootstrap/src/core/build_steps/suggest.rs
deleted file mode 100644
index fd4918961ad..00000000000
--- a/src/bootstrap/src/core/build_steps/suggest.rs
+++ /dev/null
@@ -1,68 +0,0 @@
-//! Attempt to magically identify good tests to run
-
-use std::path::PathBuf;
-use std::str::FromStr;
-
-use clap::Parser;
-
-use crate::core::build_steps::tool::Tool;
-use crate::core::builder::Builder;
-
-/// Suggests a list of possible `x.py` commands to run based on modified files in branch.
-pub fn suggest(builder: &Builder<'_>, run: bool) {
-    let git_config = builder.config.git_config();
-    let suggestions = builder
-        .tool_cmd(Tool::SuggestTests)
-        .env("SUGGEST_TESTS_NIGHTLY_BRANCH", git_config.nightly_branch)
-        .env("SUGGEST_TESTS_MERGE_COMMIT_EMAIL", git_config.git_merge_commit_email)
-        .run_capture_stdout(builder)
-        .stdout();
-
-    let suggestions = suggestions
-        .lines()
-        .map(|line| {
-            let mut sections = line.split_ascii_whitespace();
-
-            // this code expects one suggestion per line in the following format:
-            // <x_subcommand> {some number of flags} [optional stage number]
-            let cmd = sections.next().unwrap();
-            let stage = sections.next_back().and_then(|s| str::parse(s).ok());
-            let paths: Vec<PathBuf> = sections.map(|p| PathBuf::from_str(p).unwrap()).collect();
-
-            (cmd, stage, paths)
-        })
-        .collect::<Vec<_>>();
-
-    if !suggestions.is_empty() {
-        println!("==== SUGGESTIONS ====");
-        for sug in &suggestions {
-            print!("x {} ", sug.0);
-            if let Some(stage) = sug.1 {
-                print!("--stage {stage} ");
-            }
-
-            for path in &sug.2 {
-                print!("{} ", path.display());
-            }
-            println!();
-        }
-        println!("=====================");
-    } else {
-        println!("No suggestions found!");
-        return;
-    }
-
-    if run {
-        for sug in suggestions {
-            let mut build: crate::Build = builder.build.clone();
-            build.config.paths = sug.2;
-            build.config.cmd = crate::core::config::flags::Flags::parse_from(["x.py", sug.0]).cmd;
-            if let Some(stage) = sug.1 {
-                build.config.stage = stage;
-            }
-            build.build();
-        }
-    } else {
-        println!("HELP: consider using the `--run` flag to automatically run suggested tests");
-    }
-}
diff --git a/src/bootstrap/src/core/build_steps/test.rs b/src/bootstrap/src/core/build_steps/test.rs
index 757eac1475c..9e7ea5c115f 100644
--- a/src/bootstrap/src/core/build_steps/test.rs
+++ b/src/bootstrap/src/core/build_steps/test.rs
@@ -47,12 +47,11 @@ impl Step for CrateBootstrap {
     const DEFAULT: bool = true;
 
     fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
-        // This step is responsible for several different tool paths. By default
-        // it will test all of them, but requesting specific tools on the
-        // command-line (e.g. `./x test suggest-tests`) will test only the
-        // specified tools.
+        // This step is responsible for several different tool paths.
+        //
+        // By default, it will test all of them, but requesting specific tools on the command-line
+        // (e.g. `./x test src/tools/coverage-dump`) will test only the specified tools.
         run.path("src/tools/jsondoclint")
-            .path("src/tools/suggest-tests")
             .path("src/tools/replace-version-placeholder")
             .path("src/tools/coverage-dump")
             // We want `./x test tidy` to _run_ the tidy tool, not its tests.
diff --git a/src/bootstrap/src/core/build_steps/tool.rs b/src/bootstrap/src/core/build_steps/tool.rs
index 814a44b9a13..1c994b0ccfc 100644
--- a/src/bootstrap/src/core/build_steps/tool.rs
+++ b/src/bootstrap/src/core/build_steps/tool.rs
@@ -517,7 +517,6 @@ bootstrap_tool!(
     ReplaceVersionPlaceholder, "src/tools/replace-version-placeholder", "replace-version-placeholder";
     CollectLicenseMetadata, "src/tools/collect-license-metadata", "collect-license-metadata";
     GenerateCopyright, "src/tools/generate-copyright", "generate-copyright";
-    SuggestTests, "src/tools/suggest-tests", "suggest-tests";
     GenerateWindowsSys, "src/tools/generate-windows-sys", "generate-windows-sys";
     // rustdoc-gui-test has a crate dependency on compiletest, so it needs the same unstable features.
     RustdocGUITest, "src/tools/rustdoc-gui-test", "rustdoc-gui-test", is_unstable_tool = true, allow_features = COMPILETEST_ALLOW_FEATURES;
diff --git a/src/bootstrap/src/core/builder/cargo.rs b/src/bootstrap/src/core/builder/cargo.rs
index d5a290d804c..a3b471ca56e 100644
--- a/src/bootstrap/src/core/builder/cargo.rs
+++ b/src/bootstrap/src/core/builder/cargo.rs
@@ -113,7 +113,7 @@ impl Cargo {
 
         match cmd_kind {
             // No need to configure the target linker for these command types.
-            Kind::Clean | Kind::Check | Kind::Suggest | Kind::Format | Kind::Setup => {}
+            Kind::Clean | Kind::Check | Kind::Format | Kind::Setup => {}
             _ => {
                 cargo.configure_linker(builder, mode);
             }
diff --git a/src/bootstrap/src/core/builder/mod.rs b/src/bootstrap/src/core/builder/mod.rs
index 7115c5a1cbe..1b75d00b30e 100644
--- a/src/bootstrap/src/core/builder/mod.rs
+++ b/src/bootstrap/src/core/builder/mod.rs
@@ -845,7 +845,6 @@ pub enum Kind {
     #[value(alias = "r")]
     Run,
     Setup,
-    Suggest,
     Vendor,
     Perf,
 }
@@ -869,7 +868,6 @@ impl Kind {
             Kind::Install => "install",
             Kind::Run => "run",
             Kind::Setup => "setup",
-            Kind::Suggest => "suggest",
             Kind::Vendor => "vendor",
             Kind::Perf => "perf",
         }
@@ -881,7 +879,6 @@ impl Kind {
             Kind::Bench => "Benchmarking",
             Kind::Doc => "Documenting",
             Kind::Run => "Running",
-            Kind::Suggest => "Suggesting",
             Kind::Clippy => "Linting",
             Kind::Perf => "Profiling & benchmarking",
             _ => {
@@ -1201,7 +1198,7 @@ impl<'a> Builder<'a> {
             Kind::Clean => describe!(clean::CleanAll, clean::Rustc, clean::Std),
             Kind::Vendor => describe!(vendor::Vendor),
             // special-cased in Build::build()
-            Kind::Format | Kind::Suggest | Kind::Perf => vec![],
+            Kind::Format | Kind::Perf => vec![],
             Kind::MiriTest | Kind::MiriSetup => unreachable!(),
         }
     }
@@ -1269,7 +1266,6 @@ impl<'a> Builder<'a> {
             Subcommand::Run { .. } => (Kind::Run, &paths[..]),
             Subcommand::Clean { .. } => (Kind::Clean, &paths[..]),
             Subcommand::Format { .. } => (Kind::Format, &[][..]),
-            Subcommand::Suggest { .. } => (Kind::Suggest, &[][..]),
             Subcommand::Setup { profile: ref path } => (
                 Kind::Setup,
                 path.as_ref().map_or([].as_slice(), |path| std::slice::from_ref(path)),
diff --git a/src/bootstrap/src/core/config/config.rs b/src/bootstrap/src/core/config/config.rs
index 0039d44785c..28958b60fc3 100644
--- a/src/bootstrap/src/core/config/config.rs
+++ b/src/bootstrap/src/core/config/config.rs
@@ -1050,7 +1050,6 @@ impl Config {
             | Subcommand::Run { .. }
             | Subcommand::Setup { .. }
             | Subcommand::Format { .. }
-            | Subcommand::Suggest { .. }
             | Subcommand::Vendor { .. } => flags_stage.unwrap_or(0),
         };
 
@@ -1098,7 +1097,6 @@ impl Config {
                 | Subcommand::Run { .. }
                 | Subcommand::Setup { .. }
                 | Subcommand::Format { .. }
-                | Subcommand::Suggest { .. }
                 | Subcommand::Vendor { .. }
                 | Subcommand::Perf { .. } => {}
             }
diff --git a/src/bootstrap/src/core/config/flags.rs b/src/bootstrap/src/core/config/flags.rs
index 155b6f58758..1547ca44494 100644
--- a/src/bootstrap/src/core/config/flags.rs
+++ b/src/bootstrap/src/core/config/flags.rs
@@ -481,13 +481,6 @@ Arguments:
         #[arg(value_name = "<PROFILE>|hook|editor|link")]
         profile: Option<PathBuf>,
     },
-    /// Suggest a subset of tests to run, based on modified files
-    #[command(long_about = "\n")]
-    Suggest {
-        /// run suggested tests
-        #[arg(long)]
-        run: bool,
-    },
     /// Vendor dependencies
     Vendor {
         /// Additional `Cargo.toml` to sync and vendor
@@ -518,7 +511,6 @@ impl Subcommand {
             Subcommand::Install => Kind::Install,
             Subcommand::Run { .. } => Kind::Run,
             Subcommand::Setup { .. } => Kind::Setup,
-            Subcommand::Suggest { .. } => Kind::Suggest,
             Subcommand::Vendor { .. } => Kind::Vendor,
             Subcommand::Perf { .. } => Kind::Perf,
         }
diff --git a/src/bootstrap/src/core/sanity.rs b/src/bootstrap/src/core/sanity.rs
index f2119e84cce..b39d464493e 100644
--- a/src/bootstrap/src/core/sanity.rs
+++ b/src/bootstrap/src/core/sanity.rs
@@ -216,7 +216,6 @@ than building it.
             build.config.cmd,
             Subcommand::Clean { .. }
                 | Subcommand::Check { .. }
-                | Subcommand::Suggest { .. }
                 | Subcommand::Format { .. }
                 | Subcommand::Setup { .. }
         );
diff --git a/src/bootstrap/src/lib.rs b/src/bootstrap/src/lib.rs
index 66a164703b7..44be51815c7 100644
--- a/src/bootstrap/src/lib.rs
+++ b/src/bootstrap/src/lib.rs
@@ -651,11 +651,9 @@ impl Build {
         // Handle hard-coded subcommands.
         {
             #[cfg(feature = "tracing")]
-            let _hardcoded_span = span!(
-                tracing::Level::DEBUG,
-                "handling hardcoded subcommands (Format, Suggest, Perf)"
-            )
-            .entered();
+            let _hardcoded_span =
+                span!(tracing::Level::DEBUG, "handling hardcoded subcommands (Format, Perf)")
+                    .entered();
 
             match &self.config.cmd {
                 Subcommand::Format { check, all } => {
@@ -666,9 +664,6 @@ impl Build {
                         &self.config.paths,
                     );
                 }
-                Subcommand::Suggest { run } => {
-                    return core::build_steps::suggest::suggest(&builder::Builder::new(self), *run);
-                }
                 Subcommand::Perf(args) => {
                     return core::build_steps::perf::perf(&builder::Builder::new(self), args);
                 }
diff --git a/src/bootstrap/src/utils/cc_detect.rs b/src/bootstrap/src/utils/cc_detect.rs
index dcafeb80f90..778591189a3 100644
--- a/src/bootstrap/src/utils/cc_detect.rs
+++ b/src/bootstrap/src/utils/cc_detect.rs
@@ -67,7 +67,6 @@ pub fn fill_compilers(build: &mut Build) {
         // We don't need to check cross targets for these commands.
         crate::Subcommand::Clean { .. }
         | crate::Subcommand::Check { .. }
-        | crate::Subcommand::Suggest { .. }
         | crate::Subcommand::Format { .. }
         | crate::Subcommand::Setup { .. } => {
             build.hosts.iter().cloned().chain(iter::once(build.host_target)).collect()
diff --git a/src/bootstrap/src/utils/metrics.rs b/src/bootstrap/src/utils/metrics.rs
index 862c4449624..9b1ccc32cb6 100644
--- a/src/bootstrap/src/utils/metrics.rs
+++ b/src/bootstrap/src/utils/metrics.rs
@@ -43,7 +43,7 @@ pub(crate) struct BuildMetrics {
     state: RefCell<MetricsState>,
 }
 
-/// NOTE: this isn't really cloning anything, but `x suggest` doesn't need metrics so this is probably ok.
+// NOTE: this isn't really cloning anything, but necessary for `Build: Clone`.
 impl Clone for BuildMetrics {
     fn clone(&self) -> Self {
         Self::init()
diff --git a/src/tools/suggest-tests/Cargo.toml b/src/tools/suggest-tests/Cargo.toml
deleted file mode 100644
index d6f86078d7e..00000000000
--- a/src/tools/suggest-tests/Cargo.toml
+++ /dev/null
@@ -1,8 +0,0 @@
-[package]
-name = "suggest-tests"
-version = "0.1.0"
-edition = "2021"
-
-[dependencies]
-glob = "0.3.0"
-build_helper = { version = "0.1.0", path = "../../build_helper" }
diff --git a/src/tools/suggest-tests/src/dynamic_suggestions.rs b/src/tools/suggest-tests/src/dynamic_suggestions.rs
deleted file mode 100644
index f09720f1c91..00000000000
--- a/src/tools/suggest-tests/src/dynamic_suggestions.rs
+++ /dev/null
@@ -1,32 +0,0 @@
-use std::path::Path;
-
-use crate::Suggestion;
-
-type DynamicSuggestion = fn(&Path) -> Vec<Suggestion>;
-
-pub(crate) const DYNAMIC_SUGGESTIONS: &[DynamicSuggestion] = &[
-    |path: &Path| -> Vec<Suggestion> {
-        if path.starts_with("compiler/") || path.starts_with("library/") {
-            let path = path.components().take(2).collect::<Vec<_>>();
-
-            vec![Suggestion::with_single_path(
-                "test",
-                None,
-                &format!(
-                    "{}/{}",
-                    path[0].as_os_str().to_str().unwrap(),
-                    path[1].as_os_str().to_str().unwrap()
-                ),
-            )]
-        } else {
-            Vec::new()
-        }
-    },
-    |path: &Path| -> Vec<Suggestion> {
-        if path.starts_with("compiler/rustc_pattern_analysis") {
-            vec![Suggestion::new("test", None, &["tests/ui", "--test-args", "pattern"])]
-        } else {
-            Vec::new()
-        }
-    },
-];
diff --git a/src/tools/suggest-tests/src/lib.rs b/src/tools/suggest-tests/src/lib.rs
deleted file mode 100644
index cc1288c6b72..00000000000
--- a/src/tools/suggest-tests/src/lib.rs
+++ /dev/null
@@ -1,96 +0,0 @@
-use std::fmt::{self, Display};
-use std::path::Path;
-
-use dynamic_suggestions::DYNAMIC_SUGGESTIONS;
-use glob::Pattern;
-use static_suggestions::static_suggestions;
-
-mod dynamic_suggestions;
-mod static_suggestions;
-
-#[cfg(test)]
-mod tests;
-
-macro_rules! sug {
-    ($cmd:expr) => {
-        Suggestion::new($cmd, None, &[])
-    };
-
-    ($cmd:expr, $paths:expr) => {
-        Suggestion::new($cmd, None, $paths.as_slice())
-    };
-
-    ($cmd:expr, $stage:expr, $paths:expr) => {
-        Suggestion::new($cmd, Some($stage), $paths.as_slice())
-    };
-}
-
-pub(crate) use sug;
-
-pub fn get_suggestions<T: AsRef<str>>(modified_files: &[T]) -> Vec<Suggestion> {
-    let mut suggestions = Vec::new();
-
-    // static suggestions
-    for (globs, sugs) in static_suggestions().iter() {
-        let globs = globs
-            .iter()
-            .map(|glob| Pattern::new(glob).expect("Found invalid glob pattern!"))
-            .collect::<Vec<_>>();
-        let matches_some_glob = |file: &str| globs.iter().any(|glob| glob.matches(file));
-
-        if modified_files.iter().map(AsRef::as_ref).any(matches_some_glob) {
-            suggestions.extend_from_slice(sugs);
-        }
-    }
-
-    // dynamic suggestions
-    for sug in DYNAMIC_SUGGESTIONS {
-        for file in modified_files {
-            let sugs = sug(Path::new(file.as_ref()));
-
-            suggestions.extend_from_slice(&sugs);
-        }
-    }
-
-    suggestions.sort();
-    suggestions.dedup();
-
-    suggestions
-}
-
-#[derive(Clone, PartialOrd, Ord, PartialEq, Eq, Debug)]
-pub struct Suggestion {
-    pub cmd: String,
-    pub stage: Option<u32>,
-    pub paths: Vec<String>,
-}
-
-impl Suggestion {
-    pub fn new(cmd: &str, stage: Option<u32>, paths: &[&str]) -> Self {
-        Self { cmd: cmd.to_owned(), stage, paths: paths.iter().map(|p| p.to_string()).collect() }
-    }
-
-    pub fn with_single_path(cmd: &str, stage: Option<u32>, path: &str) -> Self {
-        Self::new(cmd, stage, &[path])
-    }
-}
-
-impl Display for Suggestion {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
-        write!(f, "{} ", self.cmd)?;
-
-        for path in &self.paths {
-            write!(f, "{} ", path)?;
-        }
-
-        if let Some(stage) = self.stage {
-            write!(f, "{}", stage)?;
-        } else {
-            // write a sentinel value here (in place of a stage) to be consumed
-            // by the shim in bootstrap, it will be read and ignored.
-            write!(f, "N/A")?;
-        }
-
-        Ok(())
-    }
-}
diff --git a/src/tools/suggest-tests/src/main.rs b/src/tools/suggest-tests/src/main.rs
deleted file mode 100644
index d84f8e9fa1b..00000000000
--- a/src/tools/suggest-tests/src/main.rs
+++ /dev/null
@@ -1,40 +0,0 @@
-use std::process::ExitCode;
-
-use build_helper::git::{GitConfig, get_git_modified_files};
-use suggest_tests::get_suggestions;
-
-fn main() -> ExitCode {
-    let modified_files = get_git_modified_files(
-        &GitConfig {
-            nightly_branch: &env("SUGGEST_TESTS_NIGHTLY_BRANCH"),
-            git_merge_commit_email: &env("SUGGEST_TESTS_MERGE_COMMIT_EMAIL"),
-        },
-        None,
-        &Vec::new(),
-    );
-    let modified_files = match modified_files {
-        Ok(files) => files,
-        Err(err) => {
-            eprintln!("Could not get modified files from git: \"{err}\"");
-            return ExitCode::FAILURE;
-        }
-    };
-
-    let suggestions = get_suggestions(&modified_files);
-
-    for sug in &suggestions {
-        println!("{sug}");
-    }
-
-    ExitCode::SUCCESS
-}
-
-fn env(key: &str) -> String {
-    match std::env::var(key) {
-        Ok(var) => var,
-        Err(err) => {
-            eprintln!("suggest-tests: failed to read environment variable {key}: {err}");
-            std::process::exit(1);
-        }
-    }
-}
diff --git a/src/tools/suggest-tests/src/static_suggestions.rs b/src/tools/suggest-tests/src/static_suggestions.rs
deleted file mode 100644
index d363d583b54..00000000000
--- a/src/tools/suggest-tests/src/static_suggestions.rs
+++ /dev/null
@@ -1,40 +0,0 @@
-use std::sync::OnceLock;
-
-use crate::{Suggestion, sug};
-
-// FIXME: perhaps this could use `std::lazy` when it is stabilized
-macro_rules! static_suggestions {
-    ($( [ $( $glob:expr ),* $(,)? ] => [ $( $suggestion:expr ),* $(,)? ] ),* $(,)? ) => {
-        pub(crate) fn static_suggestions() -> &'static [(Vec<&'static str>, Vec<Suggestion>)]
-        {
-            static S: OnceLock<Vec<(Vec<&'static str>, Vec<Suggestion>)>> = OnceLock::new();
-            S.get_or_init(|| vec![ $( (vec![ $($glob),* ], vec![ $($suggestion),* ]) ),*])
-        }
-    }
-}
-
-static_suggestions! {
-    ["*.md"] => [
-        sug!("test", 0, ["linkchecker"]),
-    ],
-
-    ["compiler/*"] => [
-        sug!("check"),
-        sug!("test", 1, ["tests/ui", "tests/run-make"]),
-    ],
-
-    ["compiler/rustc_mir_transform/*"] => [
-        sug!("test", 1, ["mir-opt"]),
-    ],
-
-    [
-        "compiler/rustc_mir_transform/src/coverage/*",
-        "compiler/rustc_codegen_llvm/src/coverageinfo/*",
-    ] => [
-        sug!("test", 1, ["coverage"]),
-    ],
-
-    ["src/librustdoc/*"] => [
-        sug!("test", 1, ["rustdoc"]),
-    ],
-}
diff --git a/src/tools/suggest-tests/src/tests.rs b/src/tools/suggest-tests/src/tests.rs
deleted file mode 100644
index b4149136fa3..00000000000
--- a/src/tools/suggest-tests/src/tests.rs
+++ /dev/null
@@ -1,21 +0,0 @@
-macro_rules! sugg_test {
-    ( $( $name:ident: $paths:expr => $suggestions:expr ),* ) => {
-        $(
-            #[test]
-            fn $name() {
-                let suggestions = crate::get_suggestions(&$paths).into_iter().map(|s| s.to_string()).collect::<Vec<_>>();
-                assert_eq!(suggestions, $suggestions);
-            }
-        )*
-    };
-}
-
-sugg_test! {
-    test_error_code_docs: ["compiler/rustc_error_codes/src/error_codes/E0000.md"] =>
-        ["check N/A", "test compiler/rustc_error_codes N/A", "test linkchecker 0", "test tests/ui tests/run-make 1"],
-
-    test_rustdoc: ["src/librustdoc/src/lib.rs"] => ["test rustdoc 1"],
-
-    test_rustdoc_and_libstd: ["src/librustdoc/src/lib.rs", "library/std/src/lib.rs"] =>
-        ["test library/std N/A", "test rustdoc 1"]
-}