Cover Result for question_mark

Author: dswij

clippy_lints/src/question_mark.rs

@@ -4,10 +4,10 @@ use clippy_utils::is_lang_ctor;
 use clippy_utils::source::snippet_with_applicability;
 use clippy_utils::sugg::Sugg;
 use clippy_utils::ty::is_type_diagnostic_item;
-use clippy_utils::{eq_expr_value, path_to_local_id};
+use clippy_utils::{eq_expr_value, path_to_local, path_to_local_id};
 use if_chain::if_chain;
 use rustc_errors::Applicability;
-use rustc_hir::LangItem::{OptionNone, OptionSome};
+use rustc_hir::LangItem::{OptionNone, OptionSome, ResultOk};
 use rustc_hir::{BindingAnnotation, Block, Expr, ExprKind, PatKind, StmtKind};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
@@ -48,16 +48,25 @@ impl QuestionMark {
     /// }
     /// ```
     ///
+    /// ```ignore
+    /// if result.is_err() {
+    ///     return result;
+    /// }
+    /// ```
+    ///
     /// If it matches, it will suggest to use the question mark operator instead
-    fn check_is_none_and_early_return_none(cx: &LateContext<'_>, expr: &Expr<'_>) {
+    fn check_is_none_or_err_and_early_return(cx: &LateContext<'_>, expr: &Expr<'_>) {
         if_chain! {
             if let Some(higher::If { cond, then, r#else }) = higher::If::hir(expr);
             if let ExprKind::MethodCall(segment, _, args, _) = &cond.kind;
-            if segment.ident.name == sym!(is_none);
-            if Self::expression_returns_none(cx, then);
             if let Some(subject) = args.get(0);
-            if Self::is_option(cx, subject);
-
+            if (Self::is_option(cx, subject)
+                && Self::expression_returns_none(cx, then)
+                && segment.ident.name == sym!(is_none))
+                ||
+                (Self::is_result(cx, subject)
+                && Self::expression_returns_unmodified_err(cx, then, subject)
+                && segment.ident.name == sym!(is_err));
             then {
                 let mut applicability = Applicability::MachineApplicable;
                 let receiver_str = &Sugg::hir_with_applicability(cx, subject, "..", &mut applicability);
@@ -95,31 +104,29 @@ impl QuestionMark {
         }
     }
 
-    fn check_if_let_some_and_early_return_none(cx: &LateContext<'_>, expr: &Expr<'_>) {
+    fn check_if_let_some_or_err_and_early_return(cx: &LateContext<'_>, expr: &Expr<'_>) {
         if_chain! {
             if let Some(higher::IfLet { let_pat, let_expr, if_then, if_else: Some(if_else) })
                 = higher::IfLet::hir(cx, expr);
-            if Self::is_option(cx, let_expr);
-
             if let PatKind::TupleStruct(ref path1, fields, None) = let_pat.kind;
-            if is_lang_ctor(cx, path1, OptionSome);
+            if (Self::is_option(cx, let_expr)
+                && Self::expression_returns_none(cx, if_else)
+                && is_lang_ctor(cx, path1, OptionSome))
+                ||
+                (Self::is_result(cx, let_expr)
+                 && Self::expression_returns_unmodified_err(cx, if_else, let_expr)
+                 && is_lang_ctor(cx, path1, ResultOk));
+
             if let PatKind::Binding(annot, bind_id, _, _) = fields[0].kind;
             let by_ref = matches!(annot, BindingAnnotation::Ref | BindingAnnotation::RefMut);
-
             if let ExprKind::Block(block, None) = if_then.kind;
             if block.stmts.is_empty();
             if let Some(trailing_expr) = &block.expr;
             if path_to_local_id(trailing_expr, bind_id);
-
-            if Self::expression_returns_none(cx, if_else);
             then {
                 let mut applicability = Applicability::MachineApplicable;
                 let receiver_str = snippet_with_applicability(cx, let_expr.span, "..", &mut applicability);
-                let replacement = format!(
-                    "{}{}?",
-                    receiver_str,
-                    if by_ref { ".as_ref()" } else { "" },
-                );
+                let replacement = format!("{}{}?", receiver_str, if by_ref { ".as_ref()" } else { "" },);
 
                 span_lint_and_sugg(
                     cx,
@@ -146,6 +153,12 @@ impl QuestionMark {
         is_type_diagnostic_item(cx, expr_ty, sym::Option)
     }
 
+    fn is_result(cx: &LateContext<'_>, expression: &Expr<'_>) -> bool {
+        let expr_ty = cx.typeck_results().expr_ty(expression);
+
+        is_type_diagnostic_item(cx, expr_ty, sym::Result)
+    }
+
     fn expression_returns_none(cx: &LateContext<'_>, expression: &Expr<'_>) -> bool {
         match expression.kind {
             ExprKind::Block(block, _) => {
@@ -161,6 +174,26 @@ impl QuestionMark {
         }
     }
 
+    fn expression_returns_unmodified_err(
+        cx: &LateContext<'_>,
+        expression: &Expr<'_>,
+        origin_hir_id: &Expr<'_>,
+    ) -> bool {
+        match expression.kind {
+            ExprKind::Block(block, _) => {
+                if let Some(return_expression) = Self::return_expression(block) {
+                    return Self::expression_returns_unmodified_err(cx, return_expression, origin_hir_id);
+                }
+
+                false
+            },
+            ExprKind::Ret(Some(expr)) => Self::expression_returns_unmodified_err(cx, expr, origin_hir_id),
+            ExprKind::Call(expr, _) => Self::expression_returns_unmodified_err(cx, expr, origin_hir_id),
+            ExprKind::Path(_) => path_to_local(expression) == path_to_local(origin_hir_id),
+            _ => false,
+        }
+    }
+
     fn return_expression<'tcx>(block: &Block<'tcx>) -> Option<&'tcx Expr<'tcx>> {
         // Check if last expression is a return statement. Then, return the expression
         if_chain! {
@@ -189,7 +222,7 @@ impl QuestionMark {
 
 impl<'tcx> LateLintPass<'tcx> for QuestionMark {
     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
-        Self::check_is_none_and_early_return_none(cx, expr);
-        Self::check_if_let_some_and_early_return_none(cx, expr);
+        Self::check_is_none_or_err_and_early_return(cx, expr);
+        Self::check_if_let_some_or_err_and_early_return(cx, expr);
     }
 }