New upstream version 1.52.1+dfsg1

[rustc.git] / src / tools / clippy / clippy_lints / src / transmute / useless_transmute.rs

diff --git a/src/tools/clippy/clippy_lints/src/transmute/useless_transmute.rs b/src/tools/clippy/clippy_lints/src/transmute/useless_transmute.rs
new file mode 100644 (file)
index 0000000..8344151
--- /dev/null
+++ b/src/tools/clippy/clippy_lints/src/transmute/useless_transmute.rs
@@ -0,0 +1,73 @@
+use super::USELESS_TRANSMUTE;
+use crate::utils::{span_lint, span_lint_and_then, sugg};
+use rustc_errors::Applicability;
+use rustc_hir::Expr;
+use rustc_lint::LateContext;
+use rustc_middle::ty::{self, Ty};
+
+/// Checks for `useless_transmute` lint.
+/// Returns `true` if it's triggered, otherwise returns `false`.
+pub(super) fn check<'tcx>(
+    cx: &LateContext<'tcx>,
+    e: &'tcx Expr<'_>,
+    from_ty: Ty<'tcx>,
+    to_ty: Ty<'tcx>,
+    args: &'tcx [Expr<'_>],
+) -> bool {
+    match (&from_ty.kind(), &to_ty.kind()) {
+        _ if from_ty == to_ty => {
+            span_lint(
+                cx,
+                USELESS_TRANSMUTE,
+                e.span,
+                &format!("transmute from a type (`{}`) to itself", from_ty),
+            );
+            true
+        },
+        (ty::Ref(_, rty, rty_mutbl), ty::RawPtr(ptr_ty)) => {
+            span_lint_and_then(
+                cx,
+                USELESS_TRANSMUTE,
+                e.span,
+                "transmute from a reference to a pointer",
+                |diag| {
+                    if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) {
+                        let rty_and_mut = ty::TypeAndMut {
+                            ty: rty,
+                            mutbl: *rty_mutbl,
+                        };
+
+                        let sugg = if *ptr_ty == rty_and_mut {
+                            arg.as_ty(to_ty)
+                        } else {
+                            arg.as_ty(cx.tcx.mk_ptr(rty_and_mut)).as_ty(to_ty)
+                        };
+
+                        diag.span_suggestion(e.span, "try", sugg.to_string(), Applicability::Unspecified);
+                    }
+                },
+            );
+            true
+        },
+        (ty::Int(_) | ty::Uint(_), ty::RawPtr(_)) => {
+            span_lint_and_then(
+                cx,
+                USELESS_TRANSMUTE,
+                e.span,
+                "transmute from an integer to a pointer",
+                |diag| {
+                    if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) {
+                        diag.span_suggestion(
+                            e.span,
+                            "try",
+                            arg.as_ty(&to_ty.to_string()).to_string(),
+                            Applicability::Unspecified,
+                        );
+                    }
+                },
+            );
+            true
+        },
+        _ => false,
+    }
+}