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| 1 | +use clippy_utils::diagnostics::span_lint_and_help; |
| 2 | +use rustc_hir::{def::Res, HirId, Path, PathSegment}; |
| 3 | +use rustc_lint::{LateContext, LateLintPass, Lint}; |
| 4 | +use rustc_session::{declare_lint_pass, declare_tool_lint}; |
| 5 | +use rustc_span::{sym, symbol::kw, Symbol}; |
| 6 | + |
| 7 | +declare_clippy_lint! { |
| 8 | + /// ### What it does |
| 9 | + /// |
| 10 | + /// Finds items imported through `std` when available through `core`. |
| 11 | + /// |
| 12 | + /// ### Why is this bad? |
| 13 | + /// |
| 14 | + /// Crates which have `no_std` compatibility may wish to ensure types are imported from core to ensure |
| 15 | + /// disabling `std` does not cause the crate to fail to compile. This lint is also useful for crates |
| 16 | + /// migrating to become `no_std` compatible. |
| 17 | + /// |
| 18 | + /// ### Example |
| 19 | + /// ```rust |
| 20 | + /// use std::hash::Hasher; |
| 21 | + /// ``` |
| 22 | + /// Use instead: |
| 23 | + /// ```rust |
| 24 | + /// use core::hash::Hasher; |
| 25 | + /// ``` |
| 26 | + #[clippy::version = "1.64.0"] |
| 27 | + pub STD_INSTEAD_OF_CORE, |
| 28 | + restriction, |
| 29 | + "type is imported from std when available in core" |
| 30 | +} |
| 31 | + |
| 32 | +declare_clippy_lint! { |
| 33 | + /// ### What it does |
| 34 | + /// |
| 35 | + /// Finds items imported through `std` when available through `alloc`. |
| 36 | + /// |
| 37 | + /// ### Why is this bad? |
| 38 | + /// |
| 39 | + /// Crates which have `no_std` compatibility and require alloc may wish to ensure types are imported from |
| 40 | + /// alloc to ensure disabling `std` does not cause the crate to fail to compile. This lint is also useful |
| 41 | + /// for crates migrating to become `no_std` compatible. |
| 42 | + /// |
| 43 | + /// ### Example |
| 44 | + /// ```rust |
| 45 | + /// use std::vec::Vec; |
| 46 | + /// ``` |
| 47 | + /// Use instead: |
| 48 | + /// ```rust |
| 49 | + /// # extern crate alloc; |
| 50 | + /// use alloc::vec::Vec; |
| 51 | + /// ``` |
| 52 | + #[clippy::version = "1.64.0"] |
| 53 | + pub STD_INSTEAD_OF_ALLOC, |
| 54 | + restriction, |
| 55 | + "type is imported from std when available in alloc" |
| 56 | +} |
| 57 | + |
| 58 | +declare_clippy_lint! { |
| 59 | + /// ### What it does |
| 60 | + /// |
| 61 | + /// Finds items imported through `alloc` when available through `core`. |
| 62 | + /// |
| 63 | + /// ### Why is this bad? |
| 64 | + /// |
| 65 | + /// Crates which have `no_std` compatibility and may optionally require alloc may wish to ensure types are |
| 66 | + /// imported from alloc to ensure disabling `alloc` does not cause the crate to fail to compile. This lint |
| 67 | + /// is also useful for crates migrating to become `no_std` compatible. |
| 68 | + /// |
| 69 | + /// ### Example |
| 70 | + /// ```rust |
| 71 | + /// # extern crate alloc; |
| 72 | + /// use alloc::slice::from_ref; |
| 73 | + /// ``` |
| 74 | + /// Use instead: |
| 75 | + /// ```rust |
| 76 | + /// use core::slice::from_ref; |
| 77 | + /// ``` |
| 78 | + #[clippy::version = "1.64.0"] |
| 79 | + pub ALLOC_INSTEAD_OF_CORE, |
| 80 | + restriction, |
| 81 | + "type is imported from alloc when available in core" |
| 82 | +} |
| 83 | + |
| 84 | +declare_lint_pass!(StdReexports => [STD_INSTEAD_OF_CORE, STD_INSTEAD_OF_ALLOC, ALLOC_INSTEAD_OF_CORE]); |
| 85 | + |
| 86 | +impl<'tcx> LateLintPass<'tcx> for StdReexports { |
| 87 | + fn check_path(&mut self, cx: &LateContext<'tcx>, path: &Path<'tcx>, _: HirId) { |
| 88 | + // std_instead_of_core |
| 89 | + check_path(cx, path, sym::std, sym::core, STD_INSTEAD_OF_CORE); |
| 90 | + // std_instead_of_alloc |
| 91 | + check_path(cx, path, sym::std, sym::alloc, STD_INSTEAD_OF_ALLOC); |
| 92 | + // alloc_instead_of_core |
| 93 | + check_path(cx, path, sym::alloc, sym::core, ALLOC_INSTEAD_OF_CORE); |
| 94 | + } |
| 95 | +} |
| 96 | + |
| 97 | +fn check_path(cx: &LateContext<'_>, path: &Path<'_>, krate: Symbol, suggested_crate: Symbol, lint: &'static Lint) { |
| 98 | + if_chain! { |
| 99 | + // check if path resolves to the suggested crate. |
| 100 | + if let Res::Def(_, def_id) = path.res; |
| 101 | + if suggested_crate == cx.tcx.crate_name(def_id.krate); |
| 102 | + |
| 103 | + // check if the first segment of the path is the crate we want to identify |
| 104 | + if let Some(path_root_segment) = get_first_segment(path); |
| 105 | + |
| 106 | + // check if the path matches the crate we want to suggest the other path for. |
| 107 | + if krate == path_root_segment.ident.name; |
| 108 | + then { |
| 109 | + span_lint_and_help( |
| 110 | + cx, |
| 111 | + lint, |
| 112 | + path.span, |
| 113 | + &format!("used import from `{}` instead of `{}`", krate, suggested_crate), |
| 114 | + None, |
| 115 | + &format!("consider importing the item from `{}`", suggested_crate), |
| 116 | + ); |
| 117 | + } |
| 118 | + } |
| 119 | +} |
| 120 | + |
| 121 | +/// Returns the first named segment of a [`Path`]. |
| 122 | +/// |
| 123 | +/// If this is a global path (such as `::std::fmt::Debug`), then the segment after [`kw::PathRoot`] |
| 124 | +/// is returned. |
| 125 | +fn get_first_segment<'tcx>(path: &Path<'tcx>) -> Option<&'tcx PathSegment<'tcx>> { |
| 126 | + let segment = path.segments.first()?; |
| 127 | + |
| 128 | + // A global path will have PathRoot as the first segment. In this case, return the segment after. |
| 129 | + if segment.ident.name == kw::PathRoot { |
| 130 | + path.segments.get(1) |
| 131 | + } else { |
| 132 | + Some(segment) |
| 133 | + } |
| 134 | +} |
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