[needless_return] Recursively remove unneeded semicolons

clippy_lints/src/returns.rs

@@ -1,4 +1,4 @@
-use clippy_utils::diagnostics::span_lint_hir_and_then;
+use clippy_utils::diagnostics::{span_lint_and_then, span_lint_hir_and_then};
 use clippy_utils::source::{snippet_opt, snippet_with_context};
 use clippy_utils::{fn_def_id, path_to_local_id};
 use if_chain::if_chain;
@@ -72,6 +72,27 @@ enum RetReplacement {
     Unit,
 }
 
+impl RetReplacement {
+    fn sugg_help(self) -> &'static str {
+        match self {
+            Self::Empty => "remove `return`",
+            Self::Block => "replace `return` with an empty block",
+            Self::Unit => "replace `return` with a unit value",
+        }
+    }
+}
+
+impl ToString for RetReplacement {
+    fn to_string(&self) -> String {
+        match *self {
+            Self::Empty => "",
+            Self::Block => "{}",
+            Self::Unit => "()",
+        }
+        .to_string()
+    }
+}
+
 declare_lint_pass!(Return => [LET_AND_RETURN, NEEDLESS_RETURN]);
 
 impl<'tcx> LateLintPass<'tcx> for Return {
@@ -139,62 +160,67 @@ impl<'tcx> LateLintPass<'tcx> for Return {
                 } else {
                     RetReplacement::Empty
                 };
-                check_final_expr(cx, body.value, Some(body.value.span), replacement);
+                check_final_expr(cx, body.value, vec![], replacement);
             },
             FnKind::ItemFn(..) | FnKind::Method(..) => {
-                if let ExprKind::Block(block, _) = body.value.kind {
-                    check_block_return(cx, block);
-                }
+                check_block_return(cx, &body.value.kind, vec![]);
             },
         }
     }
 }
 
-fn check_block_return<'tcx>(cx: &LateContext<'tcx>, block: &Block<'tcx>) {
-    if let Some(expr) = block.expr {
-        check_final_expr(cx, expr, Some(expr.span), RetReplacement::Empty);
-    } else if let Some(stmt) = block.stmts.iter().last() {
-        match stmt.kind {
-            StmtKind::Expr(expr) | StmtKind::Semi(expr) => {
-                check_final_expr(cx, expr, Some(stmt.span), RetReplacement::Empty);
-            },
-            _ => (),
+// if `expr` is a block, check if there are needless returns in it
+fn check_block_return<'tcx>(cx: &LateContext<'tcx>, expr_kind: &ExprKind<'tcx>, semi_spans: Vec<Span>) {
+    if let ExprKind::Block(block, _) = expr_kind {
+        if let Some(block_expr) = block.expr {
+            check_final_expr(cx, block_expr, semi_spans, RetReplacement::Empty);
+        } else if let Some(stmt) = block.stmts.iter().last() {
+            match stmt.kind {
+                StmtKind::Expr(expr) => {
+                    check_final_expr(cx, expr, semi_spans, RetReplacement::Empty);
+                },
+                StmtKind::Semi(semi_expr) => {
+                    let mut semi_spans_and_this_one = semi_spans;
+                    // we only want the span containing the semicolon so we can remove it later. From `entry.rs:382`
+                    if let Some(semicolon_span) = stmt.span.trim_start(semi_expr.span) {
+                        semi_spans_and_this_one.push(semicolon_span);
+                        check_final_expr(cx, semi_expr, semi_spans_and_this_one, RetReplacement::Empty);
+                    }
+                },
+                _ => (),
+            }
         }
     }
 }
 
 fn check_final_expr<'tcx>(
     cx: &LateContext<'tcx>,
     expr: &'tcx Expr<'tcx>,
-    span: Option<Span>,
+    semi_spans: Vec<Span>, /* containing all the places where we would need to remove semicolons if finding an
+                            * needless return */
     replacement: RetReplacement,
 ) {
-    match expr.kind {
+    let peeled_drop_expr = expr.peel_drop_temps();
+    match &peeled_drop_expr.kind {
         // simple return is always "bad"
         ExprKind::Ret(ref inner) => {
             if cx.tcx.hir().attrs(expr.hir_id).is_empty() {
                 let borrows = inner.map_or(false, |inner| last_statement_borrows(cx, inner));
                 if !borrows {
                     emit_return_lint(
                         cx,
-                        inner.map_or(expr.hir_id, |inner| inner.hir_id),
-                        span.expect("`else return` is not possible"),
+                        peeled_drop_expr.span,
+                        semi_spans,
                         inner.as_ref().map(|i| i.span),
                         replacement,
                     );
                 }
             }
         },
-        // a whole block? check it!
-        ExprKind::Block(block, _) => {
-            check_block_return(cx, block);
-        },
         ExprKind::If(_, then, else_clause_opt) => {
-            if let ExprKind::Block(ifblock, _) = then.kind {
-                check_block_return(cx, ifblock);
-            }
+            check_block_return(cx, &then.kind, semi_spans.clone());
             if let Some(else_clause) = else_clause_opt {
-                check_final_expr(cx, else_clause, None, RetReplacement::Empty);
+                check_block_return(cx, &else_clause.kind, semi_spans);
             }
         },
         // a match expr, check all arms
@@ -203,93 +229,44 @@ fn check_final_expr<'tcx>(
         // (except for unit type functions) so we don't match it
         ExprKind::Match(_, arms, MatchSource::Normal) => {
             for arm in arms.iter() {
-                check_final_expr(cx, arm.body, Some(arm.body.span), RetReplacement::Unit);
+                check_final_expr(cx, arm.body, semi_spans.clone(), RetReplacement::Unit);
             }
         },
-        ExprKind::DropTemps(expr) => check_final_expr(cx, expr, None, RetReplacement::Empty),
-        _ => (),
+        // if it's a whole block, check it
+        other_expr_kind => check_block_return(cx, other_expr_kind, semi_spans),
     }
 }
 
 fn emit_return_lint(
     cx: &LateContext<'_>,
-    emission_place: HirId,
     ret_span: Span,
+    semi_spans: Vec<Span>,
     inner_span: Option<Span>,
     replacement: RetReplacement,
 ) {
     if ret_span.from_expansion() {
         return;
     }
-    match inner_span {
-        Some(inner_span) => {
-            let mut applicability = Applicability::MachineApplicable;
-            span_lint_hir_and_then(
-                cx,
-                NEEDLESS_RETURN,
-                emission_place,
-                ret_span,
-                "unneeded `return` statement",
-                |diag| {
-                    let (snippet, _) = snippet_with_context(cx, inner_span, ret_span.ctxt(), "..", &mut applicability);
-                    diag.span_suggestion(ret_span, "remove `return`", snippet, applicability);
-                },
-            );
-        },
-        None => match replacement {
-            RetReplacement::Empty => {
-                span_lint_hir_and_then(
-                    cx,
-                    NEEDLESS_RETURN,
-                    emission_place,
-                    ret_span,
-                    "unneeded `return` statement",
-                    |diag| {
-                        diag.span_suggestion(
-                            ret_span,
-                            "remove `return`",
-                            String::new(),
-                            Applicability::MachineApplicable,
-                        );
-                    },
-                );
-            },
-            RetReplacement::Block => {
-                span_lint_hir_and_then(
-                    cx,
-                    NEEDLESS_RETURN,
-                    emission_place,
-                    ret_span,
-                    "unneeded `return` statement",
-                    |diag| {
-                        diag.span_suggestion(
-                            ret_span,
-                            "replace `return` with an empty block",
-                            "{}".to_string(),
-                            Applicability::MachineApplicable,
-                        );
-                    },
-                );
-            },
-            RetReplacement::Unit => {
-                span_lint_hir_and_then(
-                    cx,
-                    NEEDLESS_RETURN,
-                    emission_place,
-                    ret_span,
-                    "unneeded `return` statement",
-                    |diag| {
-                        diag.span_suggestion(
-                            ret_span,
-                            "replace `return` with a unit value",
-                            "()".to_string(),
-                            Applicability::MachineApplicable,
-                        );
-                    },
-                );
-            },
+    let mut applicability = Applicability::MachineApplicable;
+    let return_replacement = inner_span.map_or_else(
+        || replacement.to_string(),
+        |inner_span| {
+            let (snippet, _) = snippet_with_context(cx, inner_span, ret_span.ctxt(), "..", &mut applicability);
+            snippet.to_string()
         },
-    }
+    );
+    let sugg_help = if inner_span.is_some() {
+        "remove `return`"
+    } else {
+        replacement.sugg_help()
+    };
+    span_lint_and_then(cx, NEEDLESS_RETURN, ret_span, "unneeded `return` statement", |diag| {
+        diag.span_suggestion_hidden(ret_span, sugg_help, return_replacement, applicability);
+        // for each parent statement, we need to remove the semicolon
+        for semi_stmt_span in semi_spans {
+            diag.tool_only_span_suggestion(semi_stmt_span, "remove this semicolon", "", applicability);
+        }
+    });
 }
 
 fn last_statement_borrows<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) -> bool {

tests/ui/needless_return.fixed

@@ -233,4 +233,41 @@ fn issue_9361() -> i32 {
     return 1 + 2;
 }
 
+fn issue8336(x: i32) -> bool {
+    if x > 0 {
+        println!("something");
+        true
+    } else {
+        false
+    }
+}
+
+fn issue8156(x: u8) -> u64 {
+    match x {
+        80 => {
+            10
+        },
+        _ => {
+            100
+        },
+    }
+}
+
+// Ideally the compiler should throw `unused_braces` in this case
+fn issue9192() -> i32 {
+    {
+        0
+    }
+}
+
+fn issue9503(x: usize) -> isize {
+    unsafe {
+        if x > 12 {
+            *(x as *const isize)
+        } else {
+            !*(x as *const isize)
+        }
+    }
+}
+
 fn main() {}

tests/ui/needless_return.rs

@@ -233,4 +233,41 @@ fn issue_9361() -> i32 {
     return 1 + 2;
 }
 
+fn issue8336(x: i32) -> bool {
+    if x > 0 {
+        println!("something");
+        return true;
+    } else {
+        return false;
+    };
+}
+
+fn issue8156(x: u8) -> u64 {
+    match x {
+        80 => {
+            return 10;
+        },
+        _ => {
+            return 100;
+        },
+    };
+}
+
+// Ideally the compiler should throw `unused_braces` in this case
+fn issue9192() -> i32 {
+    {
+        return 0;
+    };
+}
+
+fn issue9503(x: usize) -> isize {
+    unsafe {
+        if x > 12 {
+            return *(x as *const isize);
+        } else {
+            return !*(x as *const isize);
+        };
+    };
+}
+
 fn main() {}