Add std_or_core util

Author: dswij

clippy_lints/src/swap.rs

@@ -2,7 +2,7 @@ use clippy_utils::diagnostics::{span_lint_and_sugg, span_lint_and_then};
 use clippy_utils::source::snippet_with_applicability;
 use clippy_utils::sugg::Sugg;
 use clippy_utils::ty::is_type_diagnostic_item;
-use clippy_utils::{can_mut_borrow_both, differing_macro_contexts, eq_expr_value, is_no_core_crate, is_no_std_crate};
+use clippy_utils::{can_mut_borrow_both, differing_macro_contexts, eq_expr_value, std_or_core};
 use if_chain::if_chain;
 use rustc_errors::Applicability;
 use rustc_hir::{BinOpKind, Block, Expr, ExprKind, PatKind, QPath, Stmt, StmtKind};
@@ -113,17 +113,7 @@ fn generate_swap_warning(cx: &LateContext<'_>, e1: &Expr<'_>, e2: &Expr<'_>, spa
 
     let first = Sugg::hir_with_applicability(cx, e1, "..", &mut applicability);
     let second = Sugg::hir_with_applicability(cx, e2, "..", &mut applicability);
-    let sugg = if !is_no_std_crate(cx) {
-        "std"
-    } else if is_no_core_crate(cx) {
-        ""
-    } else {
-        "core"
-    };
-
-    if sugg.is_empty() {
-        return;
-    }
+    let Some(sugg) = std_or_core(cx) else { return };
 
     span_lint_and_then(
         cx,
@@ -199,17 +189,7 @@ fn check_suspicious_swap(cx: &LateContext<'_>, block: &Block<'_>) {
                 };
 
                 let span = first.span.to(second.span);
-                let sugg = if !is_no_std_crate(cx) {
-                    "std"
-                } else if is_no_core_crate(cx) {
-                    ""
-                } else {
-                    "core"
-                };
-
-                if sugg.is_empty() {
-                    return;
-                }
+                let Some(sugg) = std_or_core(cx) else { return };
 
                 span_lint_and_then(cx,
                     ALMOST_SWAPPED,

clippy_utils/src/lib.rs

@@ -1846,6 +1846,16 @@ pub fn is_expr_final_block_expr(tcx: TyCtxt<'_>, expr: &Expr<'_>) -> bool {
     matches!(get_parent_node(tcx, expr.hir_id), Some(Node::Block(..)))
 }
 
+pub fn std_or_core(cx: &LateContext<'_>) -> Option<&'static str> {
+    if !is_no_std_crate(cx) {
+        Some("std")
+    } else if !is_no_core_crate(cx) {
+        Some("core")
+    } else {
+        None
+    }
+}
+
 pub fn is_no_std_crate(cx: &LateContext<'_>) -> bool {
     cx.tcx.hir().attrs(hir::CRATE_HIR_ID).iter().any(|attr| {
         if let ast::AttrKind::Normal(ref attr, _) = attr.kind {