[Parse] Avoid parsing unsafe expression before binary or postfix op (#81429)

rdar://150751248

Author: stzn

lib/Parse/ParseExpr.cpp

@@ -421,12 +421,14 @@ ParserResult<Expr> Parser::parseExprSequenceElement(Diag<> message,
 
   if (Tok.isContextualKeyword("unsafe") &&
       !(peekToken().isAtStartOfLine() ||
-        peekToken().isAny(tok::r_paren, tok::r_brace, tok::r_square,
-                          tok::equal, tok::colon, tok::comma, tok::eof) ||
+        peekToken().isAny(tok::r_paren, tok::r_brace, tok::r_square, tok::equal,
+                          tok::colon, tok::comma, tok::eof) ||
         (isExprBasic && peekToken().is(tok::l_brace)) ||
         peekToken().is(tok::period) ||
         (peekToken().isAny(tok::l_paren, tok::l_square) &&
-         peekToken().getRange().getStart() == Tok.getRange().getEnd()))) {
+         peekToken().getRange().getStart() == Tok.getRange().getEnd()) ||
+        peekToken().isBinaryOperatorLike() ||
+        peekToken().isPostfixOperatorLike())) {
     Tok.setKind(tok::contextual_keyword);
     SourceLoc unsafeLoc = consumeToken();
     ParserResult<Expr> sub =

test/Unsafe/safe.swift

@@ -200,6 +200,8 @@ func unsafeFun() {
   _ = color
 
   if unsafe { }
+
+  _ = unsafe ? 1 : 0
 }
 
 func moreUnsafeFunc(unsafe: [Int]) {
@@ -218,6 +220,13 @@ func yetMoreUnsafeFunc(unsafe: () -> Void) {
   // expected-warning@-1{{no unsafe operations occur within 'unsafe' expression}}
 }
 
+func yetMoreMoreUnsafeFunc(unsafe: Int?) {
+  _ = unsafe!
+  if let unsafe {
+    _ = unsafe + 1
+  }
+}
+
 // @safe suppresses unsafe-type-related diagnostics on an entity
 struct MyArray<Element> {
   @safe func withUnsafeBufferPointer<R, E>(