Auto merge of #3946 - rchaser53:issue-3920, r=flip1995

[rust.git] / clippy_lints / src / default_trait_access.rs

diff --git a/clippy_lints/src/default_trait_access.rs b/clippy_lints/src/default_trait_access.rs
index 0222f896e28f8371b9633e933f03c12ae6206143..247dff7560999113da19591b5586a5caa5803bdc 100644 (file)
--- a/clippy_lints/src/default_trait_access.rs
+++ b/clippy_lints/src/default_trait_access.rs
@@ -1,27 +1,30 @@
+use if_chain::if_chain;
 use rustc::hir::*;
-use rustc::lint::*;
+use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
+use rustc::ty;
+use rustc::{declare_tool_lint, lint_array};
+use rustc_errors::Applicability;
 
-use crate::utils::{match_def_path, opt_def_id, paths, span_lint_and_sugg};
+use crate::utils::{any_parent_is_automatically_derived, match_def_path, paths, span_lint_and_sugg};
 
-
-/// **What it does:** Checks for literal calls to `Default::default()`.
-///
-/// **Why is this bad?** It's more clear to the reader to use the name of the type whose default is
-/// being gotten than the generic `Default`.
-///
-/// **Known problems:** None.
-///
-/// **Example:**
-/// ```rust
-/// // Bad
-/// let s: String = Default::default();
-///
-/// // Good
-/// let s = String::default();
-/// ```
 declare_clippy_lint! {
+    /// **What it does:** Checks for literal calls to `Default::default()`.
+    ///
+    /// **Why is this bad?** It's more clear to the reader to use the name of the type whose default is
+    /// being gotten than the generic `Default`.
+    ///
+    /// **Known problems:** None.
+    ///
+    /// **Example:**
+    /// ```rust
+    /// // Bad
+    /// let s: String = Default::default();
+    ///
+    /// // Good
+    /// let s = String::default();
+    /// ```
     pub DEFAULT_TRAIT_ACCESS,
-    style,
+    pedantic,
     "checks for literal calls to Default::default()"
 }
 
@@ -32,32 +35,53 @@ impl LintPass for DefaultTraitAccess {
     fn get_lints(&self) -> LintArray {
         lint_array!(DEFAULT_TRAIT_ACCESS)
     }
+
+    fn name(&self) -> &'static str {
+        "DefaultTraitAccess"
+    }
 }
 
 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for DefaultTraitAccess {
     fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
         if_chain! {
-            if let ExprCall(ref path, ..) = expr.node;
-            if let ExprPath(ref qpath) = path.node;
-            if let Some(def_id) = opt_def_id(cx.tables.qpath_def(qpath, path.hir_id));
+            if let ExprKind::Call(ref path, ..) = expr.node;
+            if !any_parent_is_automatically_derived(cx.tcx, expr.hir_id);
+            if let ExprKind::Path(ref qpath) = path.node;
+            if let Some(def_id) = cx.tables.qpath_def(qpath, path.hir_id).opt_def_id();
             if match_def_path(cx.tcx, def_id, &paths::DEFAULT_TRAIT_METHOD);
             then {
                 match qpath {
                     QPath::Resolved(..) => {
+                        if_chain! {
+                            // Detect and ignore <Foo as Default>::default() because these calls do
+                            // explicitly name the type.
+                            if let ExprKind::Call(ref method, ref _args) = expr.node;
+                            if let ExprKind::Path(ref p) = method.node;
+                            if let QPath::Resolved(Some(_ty), _path) = p;
+                            then {
+                                return;
+                            }
+                        }
+
                         // TODO: Work out a way to put "whatever the imported way of referencing
                         // this type in this file" rather than a fully-qualified type.
-                        let replacement = format!("{}::default()", cx.tables.expr_ty(expr));
-                        span_lint_and_sugg(
-                            cx,
-                            DEFAULT_TRAIT_ACCESS,
-                            expr.span,
-                            &format!("Calling {} is more clear than this expression", replacement),
-                            "try",
-                            replacement);
+                        let expr_ty = cx.tables.expr_ty(expr);
+                        if let ty::Adt(..) = expr_ty.sty {
+                            let replacement = format!("{}::default()", expr_ty);
+                            span_lint_and_sugg(
+                                cx,
+                                DEFAULT_TRAIT_ACCESS,
+                                expr.span,
+                                &format!("Calling {} is more clear than this expression", replacement),
+                                "try",
+                                replacement,
+                                Applicability::Unspecified, // First resolve the TODO above
+                            );
+                         }
                     },
                     QPath::TypeRelative(..) => {},
                 }
             }
-         }
+        }
     }
 }