Rollup merge of #114819 - estebank:issue-78124, r=compiler-errors

Point at return type when it influences non-first `match` arm

When encountering code like

```rust
fn foo() -> i32 {
    match 0 {
        1 => return 0,
        2 => "",
        _ => 1,
    }
}
```

Point at the return type and not at the prior arm, as that arm has type `!` which isn't influencing the arm corresponding to arm `2`.

Fix #78124.

clippy_lints/src/dereference.rs

@@ -802,7 +802,8 @@ fn in_postfix_position<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'tcx>) -> boo
         match parent.kind {
             ExprKind::Call(child, _) | ExprKind::MethodCall(_, child, _, _) | ExprKind::Index(child, _, _)
                 if child.hir_id == e.hir_id => true,
-            ExprKind::Field(_, _) | ExprKind::Match(_, _, MatchSource::TryDesugar | MatchSource::AwaitDesugar) => true,
+            ExprKind::Match(.., MatchSource::TryDesugar(_) | MatchSource::AwaitDesugar)
+                | ExprKind::Field(_, _) => true,
             _ => false,
         }
     } else {

clippy_lints/src/matches/mod.rs

@@ -1038,7 +1038,7 @@ impl<'tcx> LateLintPass<'tcx> for Matches {
                 wild_in_or_pats::check(cx, arms);
             }
 
-            if source == MatchSource::TryDesugar {
+            if let MatchSource::TryDesugar(_) = source {
                 try_err::check(cx, expr, ex);
             }
 

clippy_lints/src/matches/try_err.rs

@@ -80,7 +80,7 @@ pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, scrutine
 
 /// Finds function return type by examining return expressions in match arms.
 fn find_return_type<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx ExprKind<'_>) -> Option<Ty<'tcx>> {
-    if let ExprKind::Match(_, arms, MatchSource::TryDesugar) = expr {
+    if let ExprKind::Match(_, arms, MatchSource::TryDesugar(_)) = expr {
         for arm in *arms {
             if let ExprKind::Ret(Some(ret)) = arm.body.kind {
                 return Some(cx.typeck_results().expr_ty(ret));

clippy_lints/src/methods/clone_on_copy.rs

@@ -64,7 +64,7 @@ pub(super) fn check(
                     ExprKind::Path(QPath::LangItem(rustc_hir::LangItem::TryTraitBranch, _, _))
                 ),
                 ExprKind::MethodCall(_, self_arg, ..) if expr.hir_id == self_arg.hir_id => true,
-                ExprKind::Match(_, _, MatchSource::TryDesugar | MatchSource::AwaitDesugar)
+                ExprKind::Match(_, _, MatchSource::TryDesugar(_) | MatchSource::AwaitDesugar)
                 | ExprKind::Field(..)
                 | ExprKind::Index(..) => true,
                 _ => false,

clippy_lints/src/methods/str_splitn.rs

@@ -236,7 +236,7 @@ fn indirect_usage<'tcx>(
             !matches!(
                 node,
                 Node::Expr(Expr {
-                    kind: ExprKind::Match(.., MatchSource::TryDesugar),
+                    kind: ExprKind::Match(.., MatchSource::TryDesugar(_)),
                     ..
                 })
             )

clippy_lints/src/needless_question_mark.rs

@@ -122,7 +122,7 @@ fn check(cx: &LateContext<'_>, expr: &Expr<'_>) {
         } else {
             return;
         };
-        if let ExprKind::Match(inner_expr_with_q, _, MatchSource::TryDesugar) = &arg.kind;
+        if let ExprKind::Match(inner_expr_with_q, _, MatchSource::TryDesugar(_)) = &arg.kind;
         if let ExprKind::Call(called, [inner_expr]) = &inner_expr_with_q.kind;
         if let ExprKind::Path(QPath::LangItem(LangItem::TryTraitBranch, ..)) = &called.kind;
         if expr.span.ctxt() == inner_expr.span.ctxt();

clippy_lints/src/question_mark_used.rs

@@ -34,7 +34,7 @@ declare_lint_pass!(QuestionMarkUsed => [QUESTION_MARK_USED]);
 
 impl<'tcx> LateLintPass<'tcx> for QuestionMarkUsed {
     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
-        if let ExprKind::Match(_, _, MatchSource::TryDesugar) = expr.kind {
+        if let ExprKind::Match(_, _, MatchSource::TryDesugar(_)) = expr.kind {
             if !span_is_local(expr.span) {
                 return;
             }

clippy_lints/src/redundant_closure_call.rs

@@ -52,7 +52,7 @@ impl ReturnVisitor {
 
 impl<'tcx> Visitor<'tcx> for ReturnVisitor {
     fn visit_expr(&mut self, ex: &'tcx hir::Expr<'tcx>) {
-        if let hir::ExprKind::Ret(_) | hir::ExprKind::Match(.., hir::MatchSource::TryDesugar) = ex.kind {
+        if let hir::ExprKind::Ret(_) | hir::ExprKind::Match(.., hir::MatchSource::TryDesugar(_)) = ex.kind {
             self.found_return = true;
         } else {
             hir_visit::walk_expr(self, ex);

clippy_lints/src/returns.rs

@@ -164,7 +164,7 @@ impl<'tcx> LateLintPass<'tcx> for Return {
         if !in_external_macro(cx.sess(), stmt.span)
             && let StmtKind::Semi(expr) = stmt.kind
             && let ExprKind::Ret(Some(ret)) = expr.kind
-            && let ExprKind::Match(.., MatchSource::TryDesugar) = ret.kind
+            && let ExprKind::Match(.., MatchSource::TryDesugar(_)) = ret.kind
             // Ensure this is not the final stmt, otherwise removing it would cause a compile error
             && let OwnerNode::Item(item) = cx.tcx.hir().owner(cx.tcx.hir().get_parent_item(expr.hir_id))
             && let ItemKind::Fn(_, _, body) = item.kind

clippy_lints/src/unit_types/unit_arg.rs

@@ -42,7 +42,7 @@ pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
             if cx.typeck_results().expr_ty(arg).is_unit() && !utils::is_unit_literal(arg) {
                 !matches!(
                     &arg.kind,
-                    ExprKind::Match(.., MatchSource::TryDesugar) | ExprKind::Path(..)
+                    ExprKind::Match(.., MatchSource::TryDesugar(_)) | ExprKind::Path(..)
                 )
             } else {
                 false

clippy_lints/src/useless_conversion.rs

@@ -113,7 +113,7 @@ impl<'tcx> LateLintPass<'tcx> for UselessConversion {
         }
 
         match e.kind {
-            ExprKind::Match(_, arms, MatchSource::TryDesugar) => {
+            ExprKind::Match(_, arms, MatchSource::TryDesugar(_)) => {
                 let (ExprKind::Ret(Some(e)) | ExprKind::Break(_, Some(e))) = arms[0].body.kind else {
                     return;
                 };

clippy_utils/src/check_proc_macro.rs

@@ -149,7 +149,7 @@ fn expr_search_pat(tcx: TyCtxt<'_>, e: &Expr<'_>) -> (Pat, Pat) {
             (Pat::Str("for"), Pat::Str("}"))
         },
         ExprKind::Match(_, _, MatchSource::Normal) => (Pat::Str("match"), Pat::Str("}")),
-        ExprKind::Match(e, _, MatchSource::TryDesugar) => (expr_search_pat(tcx, e).0, Pat::Str("?")),
+        ExprKind::Match(e, _, MatchSource::TryDesugar(_)) => (expr_search_pat(tcx, e).0, Pat::Str("?")),
         ExprKind::Match(e, _, MatchSource::AwaitDesugar) | ExprKind::Yield(e, YieldSource::Await { .. }) => {
             (expr_search_pat(tcx, e).0, Pat::Str("await"))
         },

clippy_utils/src/lib.rs

@@ -1765,7 +1765,7 @@ pub fn is_try<'tcx>(cx: &LateContext<'_>, expr: &'tcx Expr<'tcx>) -> Option<&'tc
 
     if let ExprKind::Match(_, arms, ref source) = expr.kind {
         // desugared from a `?` operator
-        if *source == MatchSource::TryDesugar {
+        if let MatchSource::TryDesugar(_) = *source {
             return Some(expr);
         }
 

clippy_utils/src/visitors.rs

@@ -161,7 +161,7 @@ pub fn for_each_expr_with_closures<'tcx, B, C: Continue>(
 /// returns `true` if expr contains match expr desugared from try
 fn contains_try(expr: &hir::Expr<'_>) -> bool {
     for_each_expr(expr, |e| {
-        if matches!(e.kind, hir::ExprKind::Match(_, _, hir::MatchSource::TryDesugar)) {
+        if matches!(e.kind, hir::ExprKind::Match(_, _, hir::MatchSource::TryDesugar(_))) {
             ControlFlow::Break(())
         } else {
             ControlFlow::Continue(())

tests/ui/if_same_then_else2.rs

@@ -98,7 +98,7 @@ fn if_same_then_else2() -> Result<&'static str, ()> {
     };
 
     if true {
-        //~^ ERROR: this `if` has identical blocks
+        // FIXME: should emit "this `if` has identical blocks"
         Ok("foo")?;
     } else {
         Ok("foo")?;

tests/ui/if_same_then_else2.stderr

@@ -82,25 +82,6 @@ LL | |         f32::NAN
 LL | |     };
    | |_____^
 
-error: this `if` has identical blocks
-  --> $DIR/if_same_then_else2.rs:100:13
-   |
-LL |       if true {
-   |  _____________^
-LL | |
-LL | |         Ok("foo")?;
-LL | |     } else {
-   | |_____^
-   |
-note: same as this
-  --> $DIR/if_same_then_else2.rs:103:12
-   |
-LL |       } else {
-   |  ____________^
-LL | |         Ok("foo")?;
-LL | |     }
-   | |_____^
-
 error: this `if` has identical blocks
   --> $DIR/if_same_then_else2.rs:124:20
    |
@@ -122,5 +103,5 @@ LL | |         return Ok(&foo[0..]);
 LL | |     }
    | |_____^
 
-error: aborting due to 6 previous errors
+error: aborting due to 5 previous errors