actuall add files

Author: basil-cow

clippy_lints/src/as_conversions.rs

@@ -0,0 +1,45 @@
+use rustc::lint::{in_external_macro, EarlyContext, EarlyLintPass, LintArray, LintContext, LintPass};
+use rustc::{declare_lint_pass, declare_tool_lint};
+use syntax::ast::*;
+
+use crate::utils::span_help_and_lint;
+
+declare_clippy_lint! {
+    /// **What it does:** Checks for usage of `as` conversions.
+    ///
+    /// **Why is this bad?** `as` conversions will perform many kinds of
+    /// conversions, including silently lossy conversions and dangerous coercions.
+    /// There are cases when it's necessary to use `as`, so the lint is
+    /// Allow by default.
+    ///
+    /// **Known problems:** None.
+    ///
+    /// **Example:**
+    /// ```rust
+    /// let a: u32 = 0;
+    /// let p = &a as *const u32 as *mut u32;
+    /// ```
+    pub AS_CONVERSIONS,
+    pedantic,
+    "using a potentially dangerous silent `as` conversion"
+}
+
+declare_lint_pass!(AsConversions => [AS_CONVERSIONS]);
+
+impl EarlyLintPass for AsConversions {
+    fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
+        if in_external_macro(cx.sess(), expr.span) {
+            return;
+        }
+
+        if let ExprKind::Cast(_, _) = expr.kind {
+            span_help_and_lint(
+                cx,
+                AS_CONVERSIONS,
+                expr.span,
+                "using a potentially dangerous silent `as` conversion",
+                "consider using a safe wrapper for this conversion",
+            );
+        }
+    }
+}

tests/ui/as_conversions.rs

@@ -0,0 +1,7 @@
+#[warn(clippy::as_conversions)]
+
+fn main() {
+    let i = 0u32 as u64;
+
+    let j = &i as *const u64 as *mut u64;
+}

tests/ui/as_conversions.stderr

@@ -0,0 +1,27 @@
+error: using a potentially dangerous silent `as` conversion
+  --> $DIR/as_conversions.rs:4:13
+   |
+LL |     let i = 0u32 as u64;
+   |             ^^^^^^^^^^^
+   |
+   = note: `-D clippy::as-conversions` implied by `-D warnings`
+   = help: consider using a safe wrapper for this conversion
+
+error: using a potentially dangerous silent `as` conversion
+  --> $DIR/as_conversions.rs:6:13
+   |
+LL |     let j = &i as *const u64 as *mut u64;
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = help: consider using a safe wrapper for this conversion
+
+error: using a potentially dangerous silent `as` conversion
+  --> $DIR/as_conversions.rs:6:13
+   |
+LL |     let j = &i as *const u64 as *mut u64;
+   |             ^^^^^^^^^^^^^^^^
+   |
+   = help: consider using a safe wrapper for this conversion
+
+error: aborting due to 3 previous errors
+