Auto merge of #9826 - Veykril:semi-blocks, r=Alexendoo

Add semicolon-outside/inside-block lints

changelog: Add `semicolon_outside_block` and `semicolon_inside_block` lints

Fixes https://github.com/rust-lang/rust-clippy/issues/7322

An earlier attempt at this can be found here https://github.com/rust-lang/rust-clippy/pull/7564. This PR still implements two separate lints but I am open to merging them into a single one that's configurable.

3 files changed, 141 insertions, 0 deletions

diff --git a/clippy_lints/src/declared_lints.rs b/clippy_lints/src/declared_lints.rs
index e4d76f07d6b..77c1da993dc 100644
--- a/clippy_lints/src/declared_lints.rs
+++ b/clippy_lints/src/declared_lints.rs
@@ -525,6 +525,8 @@ pub(crate) static LINTS: &[&crate::LintInfo] = &[
     crate::returns::NEEDLESS_RETURN_INFO,
     crate::same_name_method::SAME_NAME_METHOD_INFO,
     crate::self_named_constructors::SELF_NAMED_CONSTRUCTORS_INFO,
+    crate::semicolon_block::SEMICOLON_INSIDE_BLOCK_INFO,
+    crate::semicolon_block::SEMICOLON_OUTSIDE_BLOCK_INFO,
     crate::semicolon_if_nothing_returned::SEMICOLON_IF_NOTHING_RETURNED_INFO,
     crate::serde_api::SERDE_API_MISUSE_INFO,
     crate::shadow::SHADOW_REUSE_INFO,
diff --git a/clippy_lints/src/lib.rs b/clippy_lints/src/lib.rs
index e20621c96eb..bea28f7620b 100644
--- a/clippy_lints/src/lib.rs
+++ b/clippy_lints/src/lib.rs
@@ -256,6 +256,7 @@ mod return_self_not_must_use;
 mod returns;
 mod same_name_method;
 mod self_named_constructors;
+mod semicolon_block;
 mod semicolon_if_nothing_returned;
 mod serde_api;
 mod shadow;
@@ -900,6 +901,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
     store.register_late_pass(|_| Box::new(from_raw_with_void_ptr::FromRawWithVoidPtr));
     store.register_late_pass(|_| Box::new(suspicious_xor_used_as_pow::ConfusingXorAndPow));
     store.register_late_pass(move |_| Box::new(manual_is_ascii_check::ManualIsAsciiCheck::new(msrv())));
+    store.register_late_pass(|_| Box::new(semicolon_block::SemicolonBlock));
     // add lints here, do not remove this comment, it's used in `new_lint`
 }
 
diff --git a/clippy_lints/src/semicolon_block.rs b/clippy_lints/src/semicolon_block.rs
new file mode 100644
index 00000000000..8f1d1490e1f
--- /dev/null
+++ b/clippy_lints/src/semicolon_block.rs
@@ -0,0 +1,137 @@
+use clippy_utils::diagnostics::{multispan_sugg_with_applicability, span_lint_and_then};
+use rustc_errors::Applicability;
+use rustc_hir::{Block, Expr, ExprKind, Stmt, StmtKind};
+use rustc_lint::{LateContext, LateLintPass, LintContext};
+use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_span::Span;
+
+declare_clippy_lint! {
+    /// ### What it does
+    ///
+    /// Suggests moving the semicolon after a block to the inside of the block, after its last
+    /// expression.
+    ///
+    /// ### Why is this bad?
+    ///
+    /// For consistency it's best to have the semicolon inside/outside the block. Either way is fine
+    /// and this lint suggests inside the block.
+    /// Take a look at `semicolon_outside_block` for the other alternative.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// # fn f(_: u32) {}
+    /// # let x = 0;
+    /// unsafe { f(x) };
+    /// ```
+    /// Use instead:
+    /// ```rust
+    /// # fn f(_: u32) {}
+    /// # let x = 0;
+    /// unsafe { f(x); }
+    /// ```
+    #[clippy::version = "1.66.0"]
+    pub SEMICOLON_INSIDE_BLOCK,
+    restriction,
+    "add a semicolon inside the block"
+}
+declare_clippy_lint! {
+    /// ### What it does
+    ///
+    /// Suggests moving the semicolon from a block's final expression outside of the block.
+    ///
+    /// ### Why is this bad?
+    ///
+    /// For consistency it's best to have the semicolon inside/outside the block. Either way is fine
+    /// and this lint suggests outside the block.
+    /// Take a look at `semicolon_inside_block` for the other alternative.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// # fn f(_: u32) {}
+    /// # let x = 0;
+    /// unsafe { f(x); }
+    /// ```
+    /// Use instead:
+    /// ```rust
+    /// # fn f(_: u32) {}
+    /// # let x = 0;
+    /// unsafe { f(x) };
+    /// ```
+    #[clippy::version = "1.66.0"]
+    pub SEMICOLON_OUTSIDE_BLOCK,
+    restriction,
+    "add a semicolon outside the block"
+}
+declare_lint_pass!(SemicolonBlock => [SEMICOLON_INSIDE_BLOCK, SEMICOLON_OUTSIDE_BLOCK]);
+
+impl LateLintPass<'_> for SemicolonBlock {
+    fn check_stmt(&mut self, cx: &LateContext<'_>, stmt: &Stmt<'_>) {
+        match stmt.kind {
+            StmtKind::Expr(Expr {
+                kind: ExprKind::Block(block, _),
+                ..
+            }) if !block.span.from_expansion() => {
+                let Block {
+                    expr: None,
+                    stmts: [.., stmt],
+                    ..
+                } = block else { return };
+                let &Stmt {
+                    kind: StmtKind::Semi(expr),
+                    span,
+                    ..
+                } = stmt else { return };
+                semicolon_outside_block(cx, block, expr, span);
+            },
+            StmtKind::Semi(Expr {
+                kind: ExprKind::Block(block @ Block { expr: Some(tail), .. }, _),
+                ..
+            }) if !block.span.from_expansion() => semicolon_inside_block(cx, block, tail, stmt.span),
+            _ => (),
+        }
+    }
+}
+
+fn semicolon_inside_block(cx: &LateContext<'_>, block: &Block<'_>, tail: &Expr<'_>, semi_span: Span) {
+    let insert_span = tail.span.source_callsite().shrink_to_hi();
+    let remove_span = semi_span.with_lo(block.span.hi());
+
+    span_lint_and_then(
+        cx,
+        SEMICOLON_INSIDE_BLOCK,
+        semi_span,
+        "consider moving the `;` inside the block for consistent formatting",
+        |diag| {
+            multispan_sugg_with_applicability(
+                diag,
+                "put the `;` here",
+                Applicability::MachineApplicable,
+                [(remove_span, String::new()), (insert_span, ";".to_owned())],
+            );
+        },
+    );
+}
+
+fn semicolon_outside_block(cx: &LateContext<'_>, block: &Block<'_>, tail_stmt_expr: &Expr<'_>, semi_span: Span) {
+    let insert_span = block.span.with_lo(block.span.hi());
+    // account for macro calls
+    let semi_span = cx.sess().source_map().stmt_span(semi_span, block.span);
+    let remove_span = semi_span.with_lo(tail_stmt_expr.span.source_callsite().hi());
+
+    span_lint_and_then(
+        cx,
+        SEMICOLON_OUTSIDE_BLOCK,
+        block.span,
+        "consider moving the `;` outside the block for consistent formatting",
+        |diag| {
+            multispan_sugg_with_applicability(
+                diag,
+                "put the `;` here",
+                Applicability::MachineApplicable,
+                [(remove_span, String::new()), (insert_span, ";".to_owned())],
+            );
+        },
+    );
+}