Auto merge of #6190 - montrivo:manual_result_unwrap_or, r=ebroto

bors · bors · commit 29979ad0439d · 2020-10-24T23:09:14.000Z
manual_unwrap_or / support Result::unwrap_or Implements partially #5923. changelog: support Result::unwrap_or in manual_unwrap_or
diff --git a/clippy_lints/src/manual_unwrap_or.rs b/clippy_lints/src/manual_unwrap_or.rs
@@ -1,16 +1,17 @@
 use crate::consts::constant_simple;
 use crate::utils;
+use crate::utils::sugg;
 use if_chain::if_chain;
 use rustc_errors::Applicability;
-use rustc_hir::{def, Arm, Expr, ExprKind, PatKind, QPath};
+use rustc_hir::{def, Arm, Expr, ExprKind, Pat, PatKind, QPath};
 use rustc_lint::LintContext;
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::lint::in_external_macro;
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 
 declare_clippy_lint! {
     /// **What it does:**
-    /// Finds patterns that reimplement `Option::unwrap_or`.
+    /// Finds patterns that reimplement `Option::unwrap_or` or `Result::unwrap_or`.
     ///
     /// **Why is this bad?**
     /// Concise code helps focusing on behavior instead of boilerplate.
@@ -33,7 +34,7 @@ declare_clippy_lint! {
     /// ```
     pub MANUAL_UNWRAP_OR,
     complexity,
-    "finds patterns that can be encoded more concisely with `Option::unwrap_or`"
+    "finds patterns that can be encoded more concisely with `Option::unwrap_or` or `Result::unwrap_or`"
 }
 
 declare_lint_pass!(ManualUnwrapOr => [MANUAL_UNWRAP_OR]);
@@ -43,32 +44,50 @@ impl LateLintPass<'_> for ManualUnwrapOr {
         if in_external_macro(cx.sess(), expr.span) {
             return;
         }
-        lint_option_unwrap_or_case(cx, expr);
+        lint_manual_unwrap_or(cx, expr);
     }
 }
 
-fn lint_option_unwrap_or_case<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
-    fn applicable_none_arm<'a>(arms: &'a [Arm<'a>]) -> Option<&'a Arm<'a>> {
+#[derive(Copy, Clone)]
+enum Case {
+    Option,
+    Result,
+}
+
+impl Case {
+    fn unwrap_fn_path(&self) -> &str {
+        match self {
+            Case::Option => "Option::unwrap_or",
+            Case::Result => "Result::unwrap_or",
+        }
+    }
+}
+
+fn lint_manual_unwrap_or<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
+    fn applicable_or_arm<'a>(arms: &'a [Arm<'a>]) -> Option<&'a Arm<'a>> {
         if_chain! {
             if arms.len() == 2;
             if arms.iter().all(|arm| arm.guard.is_none());
-            if let Some((idx, none_arm)) = arms.iter().enumerate().find(|(_, arm)|
-                if let PatKind::Path(ref qpath) = arm.pat.kind {
-                    utils::match_qpath(qpath, &utils::paths::OPTION_NONE)
-                } else {
-                    false
+            if let Some((idx, or_arm)) = arms.iter().enumerate().find(|(_, arm)|
+                match arm.pat.kind {
+                    PatKind::Path(ref some_qpath) =>
+                        utils::match_qpath(some_qpath, &utils::paths::OPTION_NONE),
+                    PatKind::TupleStruct(ref err_qpath, &[Pat { kind: PatKind::Wild, .. }], _) =>
+                        utils::match_qpath(err_qpath, &utils::paths::RESULT_ERR),
+                    _ => false,
                 }
             );
-            let some_arm = &arms[1 - idx];
-            if let PatKind::TupleStruct(ref some_qpath, &[some_binding], _) = some_arm.pat.kind;
-            if utils::match_qpath(some_qpath, &utils::paths::OPTION_SOME);
-            if let PatKind::Binding(_, binding_hir_id, ..) = some_binding.kind;
-            if let ExprKind::Path(QPath::Resolved(_, body_path)) = some_arm.body.kind;
+            let unwrap_arm = &arms[1 - idx];
+            if let PatKind::TupleStruct(ref unwrap_qpath, &[unwrap_pat], _) = unwrap_arm.pat.kind;
+            if utils::match_qpath(unwrap_qpath, &utils::paths::OPTION_SOME)
+                || utils::match_qpath(unwrap_qpath, &utils::paths::RESULT_OK);
+            if let PatKind::Binding(_, binding_hir_id, ..) = unwrap_pat.kind;
+            if let ExprKind::Path(QPath::Resolved(_, body_path)) = unwrap_arm.body.kind;
             if let def::Res::Local(body_path_hir_id) = body_path.res;
             if body_path_hir_id == binding_hir_id;
-            if !utils::usage::contains_return_break_continue_macro(none_arm.body);
+            if !utils::usage::contains_return_break_continue_macro(or_arm.body);
             then {
-                Some(none_arm)
+                Some(or_arm)
             } else {
                 None
             }
@@ -78,24 +97,29 @@ fn lint_option_unwrap_or_case<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tc
     if_chain! {
         if let ExprKind::Match(scrutinee, match_arms, _) = expr.kind;
         let ty = cx.typeck_results().expr_ty(scrutinee);
-        if utils::is_type_diagnostic_item(cx, ty, sym!(option_type));
-        if let Some(none_arm) = applicable_none_arm(match_arms);
-        if let Some(scrutinee_snippet) = utils::snippet_opt(cx, scrutinee.span);
-        if let Some(none_body_snippet) = utils::snippet_opt(cx, none_arm.body.span);
+        if let Some(case) = if utils::is_type_diagnostic_item(cx, ty, sym!(option_type)) {
+            Some(Case::Option)
+        } else if utils::is_type_diagnostic_item(cx, ty, sym!(result_type)) {
+            Some(Case::Result)
+        } else {
+            None
+        };
+        if let Some(or_arm) = applicable_or_arm(match_arms);
+        if let Some(or_body_snippet) = utils::snippet_opt(cx, or_arm.body.span);
         if let Some(indent) = utils::indent_of(cx, expr.span);
-        if constant_simple(cx, cx.typeck_results(), none_arm.body).is_some();
+        if constant_simple(cx, cx.typeck_results(), or_arm.body).is_some();
         then {
-            let reindented_none_body =
-                utils::reindent_multiline(none_body_snippet.into(), true, Some(indent));
+            let reindented_or_body =
+                utils::reindent_multiline(or_body_snippet.into(), true, Some(indent));
             utils::span_lint_and_sugg(
                 cx,
                 MANUAL_UNWRAP_OR, expr.span,
-                "this pattern reimplements `Option::unwrap_or`",
+                &format!("this pattern reimplements `{}`", case.unwrap_fn_path()),
                 "replace with",
                 format!(
                     "{}.unwrap_or({})",
-                    scrutinee_snippet,
-                    reindented_none_body,
+                    sugg::Sugg::hir(cx, scrutinee, "..").maybe_par(),
+                    reindented_or_body,
                 ),
                 Applicability::MachineApplicable,
             );
diff --git a/src/lintlist/mod.rs b/src/lintlist/mod.rs
@@ -1190,7 +1190,7 @@ vec![
     Lint {
         name: "manual_unwrap_or",
         group: "complexity",
-        desc: "finds patterns that can be encoded more concisely with `Option::unwrap_or`",
+        desc: "finds patterns that can be encoded more concisely with `Option::unwrap_or` or `Result::unwrap_or`",
         deprecation: None,
         module: "manual_unwrap_or",
     },
diff --git a/tests/ui/manual_unwrap_or.fixed b/tests/ui/manual_unwrap_or.fixed
@@ -1,7 +1,8 @@
 // run-rustfix
 #![allow(dead_code)]
+#![allow(unused_variables)]
 
-fn unwrap_or() {
+fn option_unwrap_or() {
     // int case
     Some(1).unwrap_or(42);
 
@@ -65,4 +66,74 @@ fn unwrap_or() {
     };
 }
 
+fn result_unwrap_or() {
+    // int case
+    Ok::<i32, &str>(1).unwrap_or(42);
+
+    // int case, scrutinee is a binding
+    let a = Ok::<i32, &str>(1);
+    a.unwrap_or(42);
+
+    // int case, suggestion must surround Result expr with parenthesis
+    (Ok(1) as Result<i32, &str>).unwrap_or(42);
+
+    // method call case, suggestion must not surround Result expr `s.method()` with parenthesis
+    struct S {}
+    impl S {
+        fn method(self) -> Option<i32> {
+            Some(42)
+        }
+    }
+    let s = S {};
+    s.method().unwrap_or(42);
+
+    // int case reversed
+    Ok::<i32, &str>(1).unwrap_or(42);
+
+    // richer none expr
+    Ok::<i32, &str>(1).unwrap_or(1 + 42);
+
+    // multiline case
+    #[rustfmt::skip]
+    Ok::<i32, &str>(1).unwrap_or({
+        42 + 42
+            + 42 + 42 + 42
+            + 42 + 42 + 42
+    });
+
+    // string case
+    Ok::<&str, &str>("Bob").unwrap_or("Alice");
+
+    // don't lint
+    match Ok::<i32, &str>(1) {
+        Ok(i) => i + 2,
+        Err(_) => 42,
+    };
+    match Ok::<i32, &str>(1) {
+        Ok(i) => i,
+        Err(_) => return,
+    };
+    for j in 0..4 {
+        match Ok::<i32, &str>(j) {
+            Ok(i) => i,
+            Err(_) => continue,
+        };
+        match Ok::<i32, &str>(j) {
+            Ok(i) => i,
+            Err(_) => break,
+        };
+    }
+
+    // don't lint, Err value is used
+    match Ok::<&str, &str>("Alice") {
+        Ok(s) => s,
+        Err(s) => s,
+    };
+    // could lint, but unused_variables takes care of it
+    match Ok::<&str, &str>("Alice") {
+        Ok(s) => s,
+        Err(s) => "Bob",
+    };
+}
+
 fn main() {}
diff --git a/tests/ui/manual_unwrap_or.rs b/tests/ui/manual_unwrap_or.rs
@@ -1,7 +1,8 @@
 // run-rustfix
 #![allow(dead_code)]
+#![allow(unused_variables)]
 
-fn unwrap_or() {
+fn option_unwrap_or() {
     // int case
     match Some(1) {
         Some(i) => i,
@@ -80,4 +81,98 @@ fn unwrap_or() {
     };
 }
 
+fn result_unwrap_or() {
+    // int case
+    match Ok::<i32, &str>(1) {
+        Ok(i) => i,
+        Err(_) => 42,
+    };
+
+    // int case, scrutinee is a binding
+    let a = Ok::<i32, &str>(1);
+    match a {
+        Ok(i) => i,
+        Err(_) => 42,
+    };
+
+    // int case, suggestion must surround Result expr with parenthesis
+    match Ok(1) as Result<i32, &str> {
+        Ok(i) => i,
+        Err(_) => 42,
+    };
+
+    // method call case, suggestion must not surround Result expr `s.method()` with parenthesis
+    struct S {}
+    impl S {
+        fn method(self) -> Option<i32> {
+            Some(42)
+        }
+    }
+    let s = S {};
+    match s.method() {
+        Some(i) => i,
+        None => 42,
+    };
+
+    // int case reversed
+    match Ok::<i32, &str>(1) {
+        Err(_) => 42,
+        Ok(i) => i,
+    };
+
+    // richer none expr
+    match Ok::<i32, &str>(1) {
+        Ok(i) => i,
+        Err(_) => 1 + 42,
+    };
+
+    // multiline case
+    #[rustfmt::skip]
+    match Ok::<i32, &str>(1) {
+        Ok(i) => i,
+        Err(_) => {
+            42 + 42
+                + 42 + 42 + 42
+                + 42 + 42 + 42
+        }
+    };
+
+    // string case
+    match Ok::<&str, &str>("Bob") {
+        Ok(i) => i,
+        Err(_) => "Alice",
+    };
+
+    // don't lint
+    match Ok::<i32, &str>(1) {
+        Ok(i) => i + 2,
+        Err(_) => 42,
+    };
+    match Ok::<i32, &str>(1) {
+        Ok(i) => i,
+        Err(_) => return,
+    };
+    for j in 0..4 {
+        match Ok::<i32, &str>(j) {
+            Ok(i) => i,
+            Err(_) => continue,
+        };
+        match Ok::<i32, &str>(j) {
+            Ok(i) => i,
+            Err(_) => break,
+        };
+    }
+
+    // don't lint, Err value is used
+    match Ok::<&str, &str>("Alice") {
+        Ok(s) => s,
+        Err(s) => s,
+    };
+    // could lint, but unused_variables takes care of it
+    match Ok::<&str, &str>("Alice") {
+        Ok(s) => s,
+        Err(s) => "Bob",
+    };
+}
+
 fn main() {}
diff --git a/tests/ui/manual_unwrap_or.stderr b/tests/ui/manual_unwrap_or.stderr
