Merge pull request rust-lang#21291 from A4-Tacks/expected-nested-match-arm-expr-ty

Fix match arm nested body invalid expected type

Author: ChayimFriedman2

src/tools/rust-analyzer/crates/ide-completion/src/context/analysis.rs

@@ -734,6 +734,23 @@ fn expected_type_and_name<'db>(
                     }.map(TypeInfo::original);
                     (ty, None)
                 },
+                ast::MatchArm(it) => {
+                    let on_arrow = previous_non_trivia_token(token.clone()).is_some_and(|it| T![=>] == it.kind());
+                    let in_body = it.expr().is_some_and(|it| it.syntax().text_range().contains_range(token.text_range()));
+                    let match_expr = it.parent_match();
+
+                    let ty = if on_arrow || in_body {
+                        // match foo { ..., pat => $0 }
+                        cov_mark::hit!(expected_type_match_arm_body_without_leading_char);
+                        cov_mark::hit!(expected_type_match_arm_body_with_leading_char);
+                        sema.type_of_expr(&match_expr.into())
+                    } else {
+                        // match foo { $0 }
+                        cov_mark::hit!(expected_type_match_arm_without_leading_char);
+                        match_expr.expr().and_then(|e| sema.type_of_expr(&e))
+                    }.map(TypeInfo::original);
+                    (ty, None)
+                },
                 ast::IfExpr(it) => {
                     let ty = if let Some(body) = it.then_branch()
                         && token.text_range().end() > body.syntax().text_range().start()

src/tools/rust-analyzer/crates/ide-completion/src/context/tests.rs

@@ -256,6 +256,22 @@ fn foo() -> Foo {
     );
 }
 
+#[test]
+fn expected_type_match_arm_block_body_without_leading_char() {
+    cov_mark::check!(expected_type_match_arm_body_without_leading_char);
+    cov_mark::check!(expected_type_match_arm_body_with_leading_char);
+    check_expected_type_and_name(
+        r#"
+struct Foo;
+enum E { X }
+fn foo() -> Foo {
+    match E::X { Foo::X => { $0 } }
+}
+"#,
+        expect![[r#"ty: Foo, name: ?"#]],
+    );
+}
+
 #[test]
 fn expected_type_match_body_arm_with_leading_char() {
     cov_mark::check!(expected_type_match_arm_body_with_leading_char);

src/tools/rust-analyzer/crates/syntax/src/ast/node_ext.rs

@@ -1096,6 +1096,16 @@ impl ast::MatchGuard {
     }
 }
 
+impl ast::MatchArm {
+    pub fn parent_match(&self) -> ast::MatchExpr {
+        self.syntax()
+            .parent()
+            .and_then(|it| it.parent())
+            .and_then(ast::MatchExpr::cast)
+            .expect("MatchArms are always nested in MatchExprs")
+    }
+}
+
 impl From<ast::Item> for ast::AnyHasAttrs {
     fn from(node: ast::Item) -> Self {
         Self::new(node)