rust-clippy/clippy_lints/src/utils/internal_lints.rs

use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass, EarlyContext, EarlyLintPass};
use rustc::{declare_lint, lint_array};
use rustc::hir::*;
use rustc::hir;
use rustc::hir::intravisit::{walk_expr, NestedVisitorMap, Visitor};
use rustc_data_structures::fx::FxHashMap;
use crate::utils::{match_qpath, paths, span_lint, span_lint_and_sugg};
use syntax::symbol::LocalInternedString;
use syntax::ast::{Crate as AstCrate, Ident, ItemKind, Name};
use syntax::source_map::Span;
use std::collections::{HashMap, HashSet};


/// **What it does:** Checks for various things we like to keep tidy in clippy.
///
/// **Why is this bad?** We like to pretend we're an example of tidy code.
///
/// **Known problems:** None.
///
/// **Example:** Wrong ordering of the util::paths constants.
declare_clippy_lint! {
    pub CLIPPY_LINTS_INTERNAL,
    internal,
    "various things that will negatively affect your clippy experience"
}


/// **What it does:** Ensures every lint is associated to a `LintPass`.
///
/// **Why is this bad?** The compiler only knows lints via a `LintPass`. Without
/// putting a lint to a `LintPass::get_lints()`'s return, the compiler will not
/// know the name of the lint.
///
/// **Known problems:** Only checks for lints associated using the `lint_array!`
/// macro.
///
/// **Example:**
/// ```rust
/// declare_lint! { pub LINT_1, ... }
/// declare_lint! { pub LINT_2, ... }
/// declare_lint! { pub FORGOTTEN_LINT, ... }
/// // ...
/// pub struct Pass;
/// impl LintPass for Pass {
///     fn get_lints(&self) -> LintArray {
///         lint_array![LINT_1, LINT_2]
///         // missing FORGOTTEN_LINT
///     }
/// }
/// ```
declare_clippy_lint! {
    pub LINT_WITHOUT_LINT_PASS,
    internal,
    "declaring a lint without associating it in a LintPass"
}


/// **What it does:** Checks for the presence of the default hash types "HashMap" or "HashSet"
/// and recommends the FxHash* variants.
///
/// **Why is this bad?** The FxHash variants have better performance
/// and we don't need any collision prevention in clippy.
declare_clippy_lint! {
    pub DEFAULT_HASH_TYPES,
    internal,
    "forbid HashMap and HashSet and suggest the FxHash* variants"
}


#[derive(Copy, Clone)]
pub struct Clippy;

impl LintPass for Clippy {
    fn get_lints(&self) -> LintArray {
        lint_array!(CLIPPY_LINTS_INTERNAL)
    }
}

impl EarlyLintPass for Clippy {
    fn check_crate(&mut self, cx: &EarlyContext<'_>, krate: &AstCrate) {
        if let Some(utils) = krate
            .module
            .items
            .iter()
            .find(|item| item.ident.name == "utils")
        {
            if let ItemKind::Mod(ref utils_mod) = utils.node {
                if let Some(paths) = utils_mod
                    .items
                    .iter()
                    .find(|item| item.ident.name == "paths")
                {
                    if let ItemKind::Mod(ref paths_mod) = paths.node {
                        let mut last_name: Option<LocalInternedString> = None;
                        for item in &paths_mod.items {
                            let name = item.ident.as_str();
                            if let Some(ref last_name) = last_name {
                                if **last_name > *name {
                                    span_lint(
                                        cx,
                                        CLIPPY_LINTS_INTERNAL,
                                        item.span,
                                        "this constant should be before the previous constant due to lexical \
                                         ordering",
                                    );
                                }
                            }
                            last_name = Some(name);
                        }
                    }
                }
            }
        }
    }
}



#[derive(Clone, Debug, Default)]
pub struct LintWithoutLintPass {
    declared_lints: HashMap<Name, Span>,
    registered_lints: HashSet<Name>,
}


impl LintPass for LintWithoutLintPass {
    fn get_lints(&self) -> LintArray {
        lint_array!(LINT_WITHOUT_LINT_PASS)
    }
}


impl<'a, 'tcx> LateLintPass<'a, 'tcx> for LintWithoutLintPass {
    fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
        if let hir::ItemKind::Static(ref ty, MutImmutable, body_id) = item.node {
            if is_lint_ref_type(ty) {
                self.declared_lints.insert(item.name, item.span);
            } else if is_lint_array_type(ty) && item.name == "ARRAY" {
                if let VisibilityKind::Inherited = item.vis.node {
                    let mut collector = LintCollector {
                        output: &mut self.registered_lints,
                        cx,
                    };
                    collector.visit_expr(&cx.tcx.hir.body(body_id).value);
                }
            }
        }
    }

    fn check_crate_post(&mut self, cx: &LateContext<'a, 'tcx>, _: &'tcx Crate) {
        for (lint_name, &lint_span) in &self.declared_lints {
            // When using the `declare_lint!` macro, the original `lint_span`'s
            // file points to "<rustc macros>".
            // `compiletest-rs` thinks that's an error in a different file and
            // just ignores it. This causes the test in compile-fail/lint_pass
            // not able to capture the error.
            // Therefore, we need to climb the macro expansion tree and find the
            // actual span that invoked `declare_lint!`:
            let lint_span = lint_span
                .ctxt()
                .outer()
                .expn_info()
                .map(|ei| ei.call_site)
                .expect("unable to get call_site");

            if !self.registered_lints.contains(lint_name) {
                span_lint(
                    cx,
                    LINT_WITHOUT_LINT_PASS,
                    lint_span,
                    &format!("the lint `{}` is not added to any `LintPass`", lint_name),
                );
            }
        }
    }
}


fn is_lint_ref_type(ty: &Ty) -> bool {
    if let TyKind::Rptr(
        _,
        MutTy {
            ty: ref inner,
            mutbl: MutImmutable,
        },
    ) = ty.node
    {
        if let TyKind::Path(ref path) = inner.node {
            return match_qpath(path, &paths::LINT);
        }
    }
    false
}


fn is_lint_array_type(ty: &Ty) -> bool {
    if let TyKind::Path(ref path) = ty.node {
        match_qpath(path, &paths::LINT_ARRAY)
    } else {
        false
    }
}

struct LintCollector<'a, 'tcx: 'a> {
    output: &'a mut HashSet<Name>,
    cx: &'a LateContext<'a, 'tcx>,
}

impl<'a, 'tcx: 'a> Visitor<'tcx> for LintCollector<'a, 'tcx> {
    fn visit_expr(&mut self, expr: &'tcx Expr) {
        walk_expr(self, expr);
    }

    fn visit_path(&mut self, path: &'tcx Path, _: HirId) {
        if path.segments.len() == 1 {
            self.output.insert(path.segments[0].ident.name);
        }
    }
    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
        NestedVisitorMap::All(&self.cx.tcx.hir)
    }
}



pub struct DefaultHashTypes {
    map: FxHashMap<String, String>,
}

impl DefaultHashTypes {
    pub fn default() -> Self {
        let mut map = FxHashMap::default();
        map.insert("HashMap".to_owned(), "FxHashMap".to_owned());
        map.insert("HashSet".to_owned(), "FxHashSet".to_owned());
        Self { map }
    }
}

impl LintPass for DefaultHashTypes {
    fn get_lints(&self) -> LintArray {
        lint_array!(DEFAULT_HASH_TYPES)
    }
}

impl EarlyLintPass for DefaultHashTypes {
    fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: Ident) {
        let ident_string = ident.to_string();
        if let Some(replace) = self.map.get(&ident_string) {
            let msg = format!("Prefer {} over {}, it has better performance and we don't need any collision prevention in clippy", replace, ident_string);
            span_lint_and_sugg(cx, DEFAULT_HASH_TYPES, ident.span, &msg, "use", replace.to_owned());
        }
    }
}