Adjust the output of unnecessary_unwrap

clippy_lints/src/unwrap.rs

@@ -1,9 +1,9 @@
 use clippy_utils::diagnostics::span_lint_and_then;
 use clippy_utils::ty::is_type_diagnostic_item;
-use clippy_utils::{differing_macro_contexts, usage::is_potentially_mutated};
+use clippy_utils::{differing_macro_contexts, path_to_local, usage::is_potentially_mutated};
 use if_chain::if_chain;
 use rustc_hir::intravisit::{walk_expr, walk_fn, FnKind, NestedVisitorMap, Visitor};
-use rustc_hir::{BinOpKind, Body, Expr, ExprKind, FnDecl, HirId, Path, QPath, UnOp};
+use rustc_hir::{BinOpKind, Body, Expr, ExprKind, FnDecl, HirId, PathSegment, UnOp};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::hir::map::Map;
 use rustc_middle::lint::in_external_macro;
@@ -77,9 +77,11 @@ struct UnwrappableVariablesVisitor<'a, 'tcx> {
 #[derive(Copy, Clone, Debug)]
 struct UnwrapInfo<'tcx> {
     /// The variable that is checked
-    ident: &'tcx Path<'tcx>,
+    local_id: HirId,
     /// The check, like `x.is_ok()`
     check: &'tcx Expr<'tcx>,
+    /// The check's name, like `is_ok`
+    check_name: &'tcx PathSegment<'tcx>,
     /// The branch where the check takes place, like `if x.is_ok() { .. }`
     branch: &'tcx Expr<'tcx>,
     /// Whether `is_some()` or `is_ok()` was called (as opposed to `is_err()` or `is_none()`).
@@ -116,7 +118,7 @@ fn collect_unwrap_info<'tcx>(
     } else {
         if_chain! {
             if let ExprKind::MethodCall(method_name, _, args, _) = &expr.kind;
-            if let ExprKind::Path(QPath::Resolved(None, path)) = &args[0].kind;
+            if let Some(local_id) = path_to_local(&args[0]);
             let ty = cx.typeck_results().expr_ty(&args[0]);
             let name = method_name.ident.as_str();
             if is_relevant_option_call(cx, ty, &name) || is_relevant_result_call(cx, ty, &name);
@@ -128,7 +130,7 @@ fn collect_unwrap_info<'tcx>(
                     _ => unreachable!(),
                 };
                 let safe_to_unwrap = unwrappable != invert;
-                return vec![UnwrapInfo { ident: path, check: expr, branch, safe_to_unwrap }];
+                return vec![UnwrapInfo { local_id, check: expr, check_name: method_name, branch, safe_to_unwrap }];
             }
         }
     }
@@ -139,8 +141,8 @@ impl<'a, 'tcx> UnwrappableVariablesVisitor<'a, 'tcx> {
     fn visit_branch(&mut self, cond: &'tcx Expr<'_>, branch: &'tcx Expr<'_>, else_branch: bool) {
         let prev_len = self.unwrappables.len();
         for unwrap_info in collect_unwrap_info(self.cx, cond, branch, else_branch) {
-            if is_potentially_mutated(unwrap_info.ident, cond, self.cx)
-                || is_potentially_mutated(unwrap_info.ident, branch, self.cx)
+            if is_potentially_mutated(unwrap_info.local_id, cond, self.cx)
+                || is_potentially_mutated(unwrap_info.local_id, branch, self.cx)
             {
                 // if the variable is mutated, we don't know whether it can be unwrapped:
                 continue;
@@ -170,11 +172,11 @@ impl<'a, 'tcx> Visitor<'tcx> for UnwrappableVariablesVisitor<'a, 'tcx> {
             // find `unwrap[_err]()` calls:
             if_chain! {
                 if let ExprKind::MethodCall(method_name, _, args, _) = expr.kind;
-                if let ExprKind::Path(QPath::Resolved(None, path)) = args[0].kind;
+                if let Some(id) = path_to_local(&args[0]);
                 if [sym::unwrap, sym::expect, sym!(unwrap_err)].contains(&method_name.ident.name);
                 let call_to_unwrap = [sym::unwrap, sym::expect].contains(&method_name.ident.name);
                 if let Some(unwrappable) = self.unwrappables.iter()
-                    .find(|u| u.ident.res == path.res);
+                    .find(|u| u.local_id == id);
                 // Span contexts should not differ with the conditional branch
                 if !differing_macro_contexts(unwrappable.branch.span, expr.span);
                 if !differing_macro_contexts(unwrappable.branch.span, unwrappable.check.span);
@@ -184,10 +186,16 @@ impl<'a, 'tcx> Visitor<'tcx> for UnwrappableVariablesVisitor<'a, 'tcx> {
                             self.cx,
                             UNNECESSARY_UNWRAP,
                             expr.span,
-                            &format!("you checked before that `{}()` cannot fail, \
-                            instead of checking and unwrapping, it's better to use `if let` or `match`",
-                            method_name.ident.name),
-                            |diag| { diag.span_label(unwrappable.check.span, "the check is happening here"); },
+                            &format!(
+                                "called `{}` on `{}` after checking its variant with `{}`",
+                                method_name.ident.name,
+                                self.cx.tcx.hir().name(unwrappable.local_id),
+                                unwrappable.check_name.ident.as_str(),
+                            ),
+                            |diag| {
+                                diag.span_label(unwrappable.check.span, "the check is happening here");
+                                diag.help("try using `if let` or `match`");
+                            },
                         );
                     } else {
                         span_lint_and_then(

clippy_utils/src/usage.rs

@@ -1,10 +1,9 @@
 use crate as utils;
 use rustc_hir as hir;
-use rustc_hir::def::Res;
 use rustc_hir::intravisit;
 use rustc_hir::intravisit::{NestedVisitorMap, Visitor};
 use rustc_hir::HirIdSet;
-use rustc_hir::{Expr, ExprKind, HirId, Path};
+use rustc_hir::{Expr, ExprKind, HirId};
 use rustc_infer::infer::TyCtxtInferExt;
 use rustc_lint::LateContext;
 use rustc_middle::hir::map::Map;
@@ -35,12 +34,8 @@ pub fn mutated_variables<'tcx>(expr: &'tcx Expr<'_>, cx: &LateContext<'tcx>) ->
     Some(delegate.used_mutably)
 }
 
-pub fn is_potentially_mutated<'tcx>(variable: &'tcx Path<'_>, expr: &'tcx Expr<'_>, cx: &LateContext<'tcx>) -> bool {
-    if let Res::Local(id) = variable.res {
-        mutated_variables(expr, cx).map_or(true, |mutated| mutated.contains(&id))
-    } else {
-        true
-    }
+pub fn is_potentially_mutated<'tcx>(variable: HirId, expr: &'tcx Expr<'_>, cx: &LateContext<'tcx>) -> bool {
+    mutated_variables(expr, cx).map_or(true, |mutated| mutated.contains(&variable))
 }
 
 struct MutVarsDelegate {

tests/ui/checked_unwrap/complex_conditionals.stderr

@@ -1,4 +1,4 @@
-error: you checked before that `unwrap()` cannot fail, instead of checking and unwrapping, it's better to use `if let` or `match`
+error: called `unwrap` on `x` after checking its variant with `is_ok`
   --> $DIR/complex_conditionals.rs:8:9
    |
 LL |     if x.is_ok() && y.is_err() {
@@ -11,6 +11,7 @@ note: the lint level is defined here
    |
 LL | #![deny(clippy::panicking_unwrap, clippy::unnecessary_unwrap)]
    |                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = help: try using `if let` or `match`
 
 error: this call to `unwrap_err()` will always panic
   --> $DIR/complex_conditionals.rs:9:9
@@ -36,14 +37,16 @@ LL |     if x.is_ok() && y.is_err() {
 LL |         y.unwrap(); // will panic
    |         ^^^^^^^^^^
 
-error: you checked before that `unwrap_err()` cannot fail, instead of checking and unwrapping, it's better to use `if let` or `match`
+error: called `unwrap_err` on `y` after checking its variant with `is_err`
   --> $DIR/complex_conditionals.rs:11:9
    |
 LL |     if x.is_ok() && y.is_err() {
    |                     ---------- the check is happening here
 ...
 LL |         y.unwrap_err(); // unnecessary
    |         ^^^^^^^^^^^^^^
+   |
+   = help: try using `if let` or `match`
 
 error: this call to `unwrap()` will always panic
   --> $DIR/complex_conditionals.rs:25:9
@@ -54,14 +57,16 @@ LL |     if x.is_ok() || y.is_ok() {
 LL |         x.unwrap(); // will panic
    |         ^^^^^^^^^^
 
-error: you checked before that `unwrap_err()` cannot fail, instead of checking and unwrapping, it's better to use `if let` or `match`
+error: called `unwrap_err` on `x` after checking its variant with `is_ok`
   --> $DIR/complex_conditionals.rs:26:9
    |
 LL |     if x.is_ok() || y.is_ok() {
    |        --------- the check is happening here
 ...
 LL |         x.unwrap_err(); // unnecessary
    |         ^^^^^^^^^^^^^^
+   |
+   = help: try using `if let` or `match`
 
 error: this call to `unwrap()` will always panic
   --> $DIR/complex_conditionals.rs:27:9
@@ -72,22 +77,26 @@ LL |     if x.is_ok() || y.is_ok() {
 LL |         y.unwrap(); // will panic
    |         ^^^^^^^^^^
 
-error: you checked before that `unwrap_err()` cannot fail, instead of checking and unwrapping, it's better to use `if let` or `match`
+error: called `unwrap_err` on `y` after checking its variant with `is_ok`
   --> $DIR/complex_conditionals.rs:28:9
    |
 LL |     if x.is_ok() || y.is_ok() {
    |                     --------- the check is happening here
 ...
 LL |         y.unwrap_err(); // unnecessary
    |         ^^^^^^^^^^^^^^
+   |
+   = help: try using `if let` or `match`
 
-error: you checked before that `unwrap()` cannot fail, instead of checking and unwrapping, it's better to use `if let` or `match`
+error: called `unwrap` on `x` after checking its variant with `is_ok`
   --> $DIR/complex_conditionals.rs:32:9
    |
 LL |     if x.is_ok() && !(y.is_ok() || z.is_err()) {
    |        --------- the check is happening here
 LL |         x.unwrap(); // unnecessary
    |         ^^^^^^^^^^
+   |
+   = help: try using `if let` or `match`
 
 error: this call to `unwrap_err()` will always panic
   --> $DIR/complex_conditionals.rs:33:9
@@ -107,23 +116,27 @@ LL |     if x.is_ok() && !(y.is_ok() || z.is_err()) {
 LL |         y.unwrap(); // will panic
    |         ^^^^^^^^^^
 
-error: you checked before that `unwrap_err()` cannot fail, instead of checking and unwrapping, it's better to use `if let` or `match`
+error: called `unwrap_err` on `y` after checking its variant with `is_ok`
   --> $DIR/complex_conditionals.rs:35:9
    |
 LL |     if x.is_ok() && !(y.is_ok() || z.is_err()) {
    |                       --------- the check is happening here
 ...
 LL |         y.unwrap_err(); // unnecessary
    |         ^^^^^^^^^^^^^^
+   |
+   = help: try using `if let` or `match`
 
-error: you checked before that `unwrap()` cannot fail, instead of checking and unwrapping, it's better to use `if let` or `match`
+error: called `unwrap` on `z` after checking its variant with `is_err`
   --> $DIR/complex_conditionals.rs:36:9
    |
 LL |     if x.is_ok() && !(y.is_ok() || z.is_err()) {
    |                                    ---------- the check is happening here
 ...
 LL |         z.unwrap(); // unnecessary
    |         ^^^^^^^^^^
+   |
+   = help: try using `if let` or `match`
 
 error: this call to `unwrap_err()` will always panic
   --> $DIR/complex_conditionals.rs:37:9
@@ -143,23 +156,27 @@ LL |     if x.is_ok() || !(y.is_ok() && z.is_err()) {
 LL |         x.unwrap(); // will panic
    |         ^^^^^^^^^^
 
-error: you checked before that `unwrap_err()` cannot fail, instead of checking and unwrapping, it's better to use `if let` or `match`
+error: called `unwrap_err` on `x` after checking its variant with `is_ok`
   --> $DIR/complex_conditionals.rs:46:9
    |
 LL |     if x.is_ok() || !(y.is_ok() && z.is_err()) {
    |        --------- the check is happening here
 ...
 LL |         x.unwrap_err(); // unnecessary
    |         ^^^^^^^^^^^^^^
+   |
+   = help: try using `if let` or `match`
 
-error: you checked before that `unwrap()` cannot fail, instead of checking and unwrapping, it's better to use `if let` or `match`
+error: called `unwrap` on `y` after checking its variant with `is_ok`
   --> $DIR/complex_conditionals.rs:47:9
    |
 LL |     if x.is_ok() || !(y.is_ok() && z.is_err()) {
    |                       --------- the check is happening here
 ...
 LL |         y.unwrap(); // unnecessary
    |         ^^^^^^^^^^
+   |
+   = help: try using `if let` or `match`
 
 error: this call to `unwrap_err()` will always panic
   --> $DIR/complex_conditionals.rs:48:9
@@ -179,14 +196,16 @@ LL |     if x.is_ok() || !(y.is_ok() && z.is_err()) {
 LL |         z.unwrap(); // will panic
    |         ^^^^^^^^^^
 
-error: you checked before that `unwrap_err()` cannot fail, instead of checking and unwrapping, it's better to use `if let` or `match`
+error: called `unwrap_err` on `z` after checking its variant with `is_err`
   --> $DIR/complex_conditionals.rs:50:9
    |
 LL |     if x.is_ok() || !(y.is_ok() && z.is_err()) {
    |                                    ---------- the check is happening here
 ...
 LL |         z.unwrap_err(); // unnecessary
    |         ^^^^^^^^^^^^^^
+   |
+   = help: try using `if let` or `match`
 
 error: aborting due to 20 previous errors
 

tests/ui/checked_unwrap/complex_conditionals_nested.stderr

@@ -1,4 +1,4 @@
-error: you checked before that `unwrap()` cannot fail, instead of checking and unwrapping, it's better to use `if let` or `match`
+error: called `unwrap` on `x` after checking its variant with `is_some`
   --> $DIR/complex_conditionals_nested.rs:8:13
    |
 LL |         if x.is_some() {
@@ -11,6 +11,7 @@ note: the lint level is defined here
    |
 LL | #![deny(clippy::panicking_unwrap, clippy::unnecessary_unwrap)]
    |                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = help: try using `if let` or `match`
 
 error: this call to `unwrap()` will always panic
   --> $DIR/complex_conditionals_nested.rs:10:13