Improve parsing errors and suggestions for bad if statements

1 files changed, 16 insertions, 3 deletions

diff --git a/compiler/rustc_parse/src/parser/stmt.rs b/compiler/rustc_parse/src/parser/stmt.rs
index 42355dd93a7..51bd9d2d386 100644
--- a/compiler/rustc_parse/src/parser/stmt.rs
+++ b/compiler/rustc_parse/src/parser/stmt.rs
@@ -432,10 +432,23 @@ impl<'a> Parser<'a> {
         //
         // which is valid in other languages, but not Rust.
         match self.parse_stmt_without_recovery(false, ForceCollect::No) {
-            // If the next token is an open brace (e.g., `if a b {`), the place-
-            // inside-a-block suggestion would be more likely wrong than right.
+            // If the next token is an open brace, e.g., we have:
+            //
+            //     if expr other_expr {
+            //        ^    ^          ^- lookahead(1) is a brace
+            //        |    |- current token is not "else"
+            //        |- (statement we just parsed)
+            //
+            // the place-inside-a-block suggestion would be more likely wrong than right.
+            //
+            // FIXME(compiler-errors): this should probably parse an arbitrary expr and not
+            // just lookahead one token, so we can see if there's a brace after _that_,
+            // since we want to protect against:
+            //     `if 1 1 + 1 {` being suggested as  `if { 1 } 1 + 1 {`
+            //                                            +   +
             Ok(Some(_))
-                if self.look_ahead(1, |t| t == &token::OpenDelim(Delimiter::Brace))
+                if (!self.token.is_keyword(kw::Else)
+                    && self.look_ahead(1, |t| t == &token::OpenDelim(Delimiter::Brace)))
                     || do_not_suggest_help => {}
             // Do not suggest `if foo println!("") {;}` (as would be seen in test for #46836).
             Ok(Some(Stmt { kind: StmtKind::Empty, .. })) => {}