1 files changed, 12 insertions, 0 deletions
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 84e3d8ddf70..2b2f925306d 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -2965,6 +2965,18 @@ impl<'a> Parser<'a> {
         }
         let lo = self.prev_span;
         let cond = self.parse_expr_res(RESTRICTION_NO_STRUCT_LITERAL, None)?;
+
+        // Verify that the parsed `if` condition makes sense as a condition. If it is a block, then
+        // verify that the last statement is either an implicit return (no `;`) or an explicit
+        // return. This won't catch blocks with an explicit `return`, but that would be caught by
+        // the dead code lint.
+        if self.eat_keyword(keywords::Else) || !cond.returns() {
+            let sp = lo.next_point();
+            let mut err = self.diagnostic()
+                .struct_span_err(sp, "missing condition for `if` statemement");
+            err.span_label(sp, "expected if condition here");
+            return Err(err)
+        }
         let thn = self.parse_block()?;
         let mut els: Option<P<Expr>> = None;
         let mut hi = thn.span;