std_instead_of_core and friends

CHANGELOG.md

@@ -3901,6 +3901,7 @@ Released 2018-09-13
 [`skip_while_next`]: https://rust-lang.github.io/rust-clippy/master/index.html#skip_while_next
 [`slow_vector_initialization`]: https://rust-lang.github.io/rust-clippy/master/index.html#slow_vector_initialization
 [`stable_sort_primitive`]: https://rust-lang.github.io/rust-clippy/master/index.html#stable_sort_primitive
+[`std_instead_of_core`]: https://rust-lang.github.io/rust-clippy/master/index.html#std_instead_of_core
 [`str_to_string`]: https://rust-lang.github.io/rust-clippy/master/index.html#str_to_string
 [`string_add`]: https://rust-lang.github.io/rust-clippy/master/index.html#string_add
 [`string_add_assign`]: https://rust-lang.github.io/rust-clippy/master/index.html#string_add_assign

clippy_lints/src/lib.register_lints.rs

@@ -497,6 +497,7 @@ store.register_lints(&[
     size_of_in_element_count::SIZE_OF_IN_ELEMENT_COUNT,
     slow_vector_initialization::SLOW_VECTOR_INITIALIZATION,
     stable_sort_primitive::STABLE_SORT_PRIMITIVE,
+    std_instead_of_core::STD_INSTEAD_OF_CORE,
     strings::STRING_ADD,
     strings::STRING_ADD_ASSIGN,
     strings::STRING_FROM_UTF8_AS_BYTES,

clippy_lints/src/lib.register_nursery.rs

@@ -25,6 +25,7 @@ store.register_group(true, "clippy::nursery", Some("clippy_nursery"), vec![
     LintId::of(path_buf_push_overwrite::PATH_BUF_PUSH_OVERWRITE),
     LintId::of(redundant_pub_crate::REDUNDANT_PUB_CRATE),
     LintId::of(regex::TRIVIAL_REGEX),
+    LintId::of(std_instead_of_core::STD_INSTEAD_OF_CORE),
     LintId::of(strings::STRING_LIT_AS_BYTES),
     LintId::of(suspicious_operation_groupings::SUSPICIOUS_OPERATION_GROUPINGS),
     LintId::of(trailing_empty_array::TRAILING_EMPTY_ARRAY),

clippy_lints/src/lib.rs

@@ -365,6 +365,7 @@ mod single_component_path_imports;
 mod size_of_in_element_count;
 mod slow_vector_initialization;
 mod stable_sort_primitive;
+mod std_instead_of_core;
 mod strings;
 mod strlen_on_c_strings;
 mod suspicious_operation_groupings;
@@ -915,6 +916,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
     let verbose_bit_mask_threshold = conf.verbose_bit_mask_threshold;
     store.register_late_pass(move || Box::new(operators::Operators::new(verbose_bit_mask_threshold)));
     store.register_late_pass(|| Box::new(invalid_utf8_in_unchecked::InvalidUtf8InUnchecked));
+    store.register_late_pass(|| Box::new(std_instead_of_core::StdReexports));
     // add lints here, do not remove this comment, it's used in `new_lint`
 }
 

clippy_lints/src/std_instead_of_core.rs

@@ -0,0 +1,72 @@
+use clippy_utils::diagnostics::span_lint_and_help;
+use rustc_hir::{def::Res, Item, ItemKind};
+use rustc_lint::{LateContext, LateLintPass, Lint};
+use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_span::{sym, Symbol};
+
+declare_clippy_lint! {
+    /// ### What it does
+    ///
+    /// ### Why is this bad?
+    ///
+    /// ### Example
+    /// ```rust
+    /// // example code where clippy issues a warning
+    /// ```
+    /// Use instead:
+    /// ```rust
+    /// // example code which does not raise clippy warning
+    /// ```
+    #[clippy::version = "1.64.0"]
+    pub STD_INSTEAD_OF_CORE,
+    nursery,
+    "default lint description"
+}
+// TODO: Make multi pass: see DropForgetRef
+declare_lint_pass!(StdReexports => [STD_INSTEAD_OF_CORE]);
+
+impl<'tcx> LateLintPass<'tcx> for StdReexports {
+    fn check_item(&mut self, cx: &LateContext<'tcx>, item: &Item<'tcx>) {
+        // std_instead_of_core
+        run_lint(cx, item, sym::core, sym::std, STD_INSTEAD_OF_CORE);
+        // std_instead_of_alloc
+        run_lint(cx, item, sym::alloc, sym::std, STD_INSTEAD_OF_CORE);
+        // alloc_instead_of_core
+        run_lint(cx, item, sym::core, sym::alloc, STD_INSTEAD_OF_CORE);
+    }
+
+    // TODO: Fully qualified items
+    // - `std::vec::Vec::<u32>::new()`
+}
+
+fn run_lint(
+    cx: &LateContext<'_>,
+    item: &Item<'_>,
+    item_crate_name: Symbol,
+    use_crate_segment_name: Symbol,
+    lint: &'static Lint,
+) {
+    if_chain! {
+        if let ItemKind::Use(path, _) = item.kind;
+        if let Res::Def(_, def_id) = path.res;
+        // check if the resolved path is in the crate
+        if item_crate_name == cx.tcx.crate_name(def_id.krate);
+
+        // check if the first segment of the path is from std or
+        if let Some(path_root_segment) = path.segments.first();
+
+        // and check that the first segment of the import refers crate we lint for.
+        if use_crate_segment_name == path_root_segment.ident.name;
+
+        then {
+            span_lint_and_help(
+                cx,
+                lint,
+                path.span,
+                &format!("used `{}` import instead of `{}`", use_crate_segment_name, item_crate_name),
+                None,
+                &format!("consider importing from `{}`", item_crate_name),
+            );
+        }
+    }
+}

tests/ui/std_instead_of_core.rs

@@ -0,0 +1,13 @@
+#![warn(clippy::std_instead_of_core)]
+#![allow(unused_imports)]
+
+extern crate alloc;
+
+use alloc::slice::from_ref;
+use std::hash::Hasher;
+use std::vec::Vec;
+
+fn main() {
+    let test1 = alloc::vec::Vec::<u32>::new();
+    let test = ::std::vec::Vec::<u32>::new();
+}