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.

12 files changed, 10 insertions, 102 deletions

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()