Auto merge of rust-lang#10470 - Alexendoo:match-single-binding-semico…

…lon, r=giraffate

Fix semicolon insertion in `match_single_binding`

changelog: [`match_single_binding`]: Fix missing semicolon after the suggestion

Fixes rust-lang#10447

Also fixes an edge case for unit returning macros in expression contexts:

```rust
f(match 1 {
    _ => println!("foo"),
});
```

would suggest

```rust
f(println!("foo"););
```

clippy_lints/src/matches/match_single_binding.rs

@@ -3,7 +3,7 @@ use clippy_utils::macros::HirNode;
 use clippy_utils::source::{indent_of, snippet, snippet_block_with_context, snippet_with_applicability};
 use clippy_utils::{get_parent_expr, is_refutable, peel_blocks};
 use rustc_errors::Applicability;
-use rustc_hir::{Arm, Expr, ExprKind, Node, PatKind};
+use rustc_hir::{Arm, Expr, ExprKind, Node, PatKind, StmtKind};
 use rustc_lint::LateContext;
 use rustc_span::Span;
 
@@ -24,22 +24,27 @@ pub(crate) fn check<'a>(cx: &LateContext<'a>, ex: &Expr<'a>, arms: &[Arm<'_>], e
     let bind_names = arms[0].pat.span;
     let match_body = peel_blocks(arms[0].body);
     let mut app = Applicability::MaybeIncorrect;
-    let (snippet_body, from_macro) = snippet_block_with_context(
+    let mut snippet_body = snippet_block_with_context(
         cx,
         match_body.span,
         arms[0].span.ctxt(),
         "..",
         Some(expr.span),
         &mut app,
-    );
-    let mut snippet_body = snippet_body.to_string();
+    )
+    .0
+    .to_string();
 
     // Do we need to add ';' to suggestion ?
-    if matches!(match_body.kind, ExprKind::Block(..)) {
-        // macro + expr_ty(body) == ()
-        if from_macro && cx.typeck_results().expr_ty(match_body).is_unit() {
-            snippet_body.push(';');
+    if let Node::Stmt(stmt) = cx.tcx.hir().get_parent(expr.hir_id)
+        && let StmtKind::Expr(_) = stmt.kind
+        && match match_body.kind {
+            // We don't need to add a ; to blocks, unless that block is from a macro expansion
+            ExprKind::Block(block, _) => block.span.from_expansion(),
+            _ => true,
         }
+    {
+        snippet_body.push(';');
     }
 
     match arms[0].pat.kind {

tests/ui/match_single_binding.fixed

@@ -1,7 +1,12 @@
 // run-rustfix
 #![warn(clippy::match_single_binding)]
-#![allow(unused_variables)]
-#![allow(clippy::toplevel_ref_arg, clippy::uninlined_format_args)]
+#![allow(
+    unused,
+    clippy::let_unit_value,
+    clippy::no_effect,
+    clippy::toplevel_ref_arg,
+    clippy::uninlined_format_args
+)]
 
 struct Point {
     x: i32,
@@ -109,10 +114,9 @@ fn main() {
 
     // Lint
     let x = 1;
-    println!("Not an array index start");
+    println!("Not an array index start")
 }
 
-#[allow(dead_code)]
 fn issue_8723() {
     let (mut val, idx) = ("a b", 1);
 
@@ -125,16 +129,15 @@ fn issue_8723() {
     let _ = val;
 }
 
-#[allow(dead_code)]
+fn side_effects() {}
+
 fn issue_9575() {
-    fn side_effects() {}
     let _ = || {
         side_effects();
-        println!("Needs curlies");
+        println!("Needs curlies")
     };
 }
 
-#[allow(dead_code)]
 fn issue_9725(r: Option<u32>) {
     let x = r;
     match x {
@@ -146,3 +149,25 @@ fn issue_9725(r: Option<u32>) {
         },
     };
 }
+
+fn issue_10447() -> usize {
+    ();
+
+    let a = ();
+
+    side_effects();
+
+    let b = side_effects();
+
+    println!("1");
+
+    let c = println!("1");
+
+    let in_expr = [
+        (),
+        side_effects(),
+        println!("1"),
+    ];
+
+    2
+}

tests/ui/match_single_binding.rs

@@ -1,7 +1,12 @@
 // run-rustfix
 #![warn(clippy::match_single_binding)]
-#![allow(unused_variables)]
-#![allow(clippy::toplevel_ref_arg, clippy::uninlined_format_args)]
+#![allow(
+    unused,
+    clippy::let_unit_value,
+    clippy::no_effect,
+    clippy::toplevel_ref_arg,
+    clippy::uninlined_format_args
+)]
 
 struct Point {
     x: i32,
@@ -127,7 +132,6 @@ fn main() {
     }
 }
 
-#[allow(dead_code)]
 fn issue_8723() {
     let (mut val, idx) = ("a b", 1);
 
@@ -141,15 +145,14 @@ fn issue_8723() {
     let _ = val;
 }
 
-#[allow(dead_code)]
+fn side_effects() {}
+
 fn issue_9575() {
-    fn side_effects() {}
     let _ = || match side_effects() {
         _ => println!("Needs curlies"),
     };
 }
 
-#[allow(dead_code)]
 fn issue_9725(r: Option<u32>) {
     match r {
         x => match x {
@@ -162,3 +165,43 @@ fn issue_9725(r: Option<u32>) {
         },
     };
 }
+
+fn issue_10447() -> usize {
+    match 1 {
+        _ => (),
+    }
+
+    let a = match 1 {
+        _ => (),
+    };
+
+    match 1 {
+        _ => side_effects(),
+    }
+
+    let b = match 1 {
+        _ => side_effects(),
+    };
+
+    match 1 {
+        _ => println!("1"),
+    }
+
+    let c = match 1 {
+        _ => println!("1"),
+    };
+
+    let in_expr = [
+        match 1 {
+            _ => (),
+        },
+        match 1 {
+            _ => side_effects(),
+        },
+        match 1 {
+            _ => println!("1"),
+        },
+    ];
+
+    2
+}