Auto merge of #7477 - F3real:needless_continue, r=flip1995

Enhance needless continue to detect loop {continue;}

Fixes #7417

changelog: Report [`needless_continue`] in `loop { continue; }` case

clippy_lints/src/needless_continue.rs

@@ -273,6 +273,8 @@ struct LintData<'a> {
     block_stmts: &'a [ast::Stmt],
 }
 
+const MSG_REDUNDANT_CONTINUE_EXPRESSION: &str = "this `continue` expression is redundant";
+
 const MSG_REDUNDANT_ELSE_BLOCK: &str = "this `else` block is redundant";
 
 const MSG_ELSE_BLOCK_NOT_NEEDED: &str = "there is no need for an explicit `else` block for this `if` \
@@ -283,6 +285,8 @@ const DROP_ELSE_BLOCK_AND_MERGE_MSG: &str = "consider dropping the `else` clause
 
 const DROP_ELSE_BLOCK_MSG: &str = "consider dropping the `else` clause";
 
+const DROP_CONTINUE_EXPRESSION_MSG: &str = "consider dropping the `continue` expression";
+
 fn emit_warning<'a>(cx: &EarlyContext<'_>, data: &'a LintData<'_>, header: &str, typ: LintType) {
     // snip    is the whole *help* message that appears after the warning.
     // message is the warning message.
@@ -364,6 +368,22 @@ fn suggestion_snippet_for_continue_inside_else<'a>(cx: &EarlyContext<'_>, data:
 }
 
 fn check_and_warn<'a>(cx: &EarlyContext<'_>, expr: &'a ast::Expr) {
+    if_chain! {
+        if let ast::ExprKind::Loop(loop_block, ..) = &expr.kind;
+        if let Some(last_stmt) = loop_block.stmts.last();
+        if let ast::StmtKind::Expr(inner_expr) | ast::StmtKind::Semi(inner_expr) = &last_stmt.kind;
+        if let ast::ExprKind::Continue(_) = inner_expr.kind;
+        then {
+            span_lint_and_help(
+                cx,
+                NEEDLESS_CONTINUE,
+                last_stmt.span,
+                MSG_REDUNDANT_CONTINUE_EXPRESSION,
+                None,
+                DROP_CONTINUE_EXPRESSION_MSG,
+            );
+        }
+    }
     with_loop_block(expr, |loop_block, label| {
         for (i, stmt) in loop_block.stmts.iter().enumerate() {
             with_if_expr(stmt, |if_expr, cond, then_block, else_expr| {

tests/ui/needless_continue.rs

@@ -51,6 +51,34 @@ fn main() {
     }
 }
 
+fn simple_loop() {
+    loop {
+        continue; // should lint here
+    }
+}
+
+fn simple_loop2() {
+    loop {
+        println!("bleh");
+        continue; // should lint here
+    }
+}
+
+#[rustfmt::skip]
+fn simple_loop3() {
+    loop {
+        continue // should lint here
+    }
+}
+
+#[rustfmt::skip]
+fn simple_loop4() {
+    loop {
+        println!("bleh");
+        continue // should lint here
+    }
+}
+
 mod issue_2329 {
     fn condition() -> bool {
         unimplemented!()

tests/ui/needless_continue.stderr

@@ -54,8 +54,40 @@ LL | |         }
                        println!("Jabber");
                    }
 
+error: this `continue` expression is redundant
+  --> $DIR/needless_continue.rs:56:9
+   |
+LL |         continue; // should lint here
+   |         ^^^^^^^^^
+   |
+   = help: consider dropping the `continue` expression
+
+error: this `continue` expression is redundant
+  --> $DIR/needless_continue.rs:63:9
+   |
+LL |         continue; // should lint here
+   |         ^^^^^^^^^
+   |
+   = help: consider dropping the `continue` expression
+
+error: this `continue` expression is redundant
+  --> $DIR/needless_continue.rs:70:9
+   |
+LL |         continue // should lint here
+   |         ^^^^^^^^
+   |
+   = help: consider dropping the `continue` expression
+
+error: this `continue` expression is redundant
+  --> $DIR/needless_continue.rs:78:9
+   |
+LL |         continue // should lint here
+   |         ^^^^^^^^
+   |
+   = help: consider dropping the `continue` expression
+
 error: this `else` block is redundant
-  --> $DIR/needless_continue.rs:100:24
+  --> $DIR/needless_continue.rs:128:24
    |
 LL |                   } else {
    |  ________________________^
@@ -78,7 +110,7 @@ LL | |                 }
                            }
 
 error: there is no need for an explicit `else` block for this `if` expression
-  --> $DIR/needless_continue.rs:106:17
+  --> $DIR/needless_continue.rs:134:17
    |
 LL | /                 if condition() {
 LL | |                     continue; // should lint here
@@ -95,5 +127,5 @@ LL | |                 }
                                println!("bar-5");
                            }
 
-error: aborting due to 4 previous errors
+error: aborting due to 8 previous errors