From 6cf56e9eb712d8fffee0ea7142d2644603b6e13d Mon Sep 17 00:00:00 2001
From: Doug Gregor <dgregor@apple.com>
Date: Fri, 7 Mar 2025 10:17:45 -0800
Subject: [PATCH] SE-0458: Disambiguate postfix expressions vs. unsafe
 expressions more generally

Handle call-vs-tuple and subscript-vs-collection-expr disambiguation using the
same "no trivia" rule that we used to disambiguite "unsafe.x" (which we
treat as a member access) from "unsafe .x" (which we treat as an unsafe
expression with a leading-dot member access).

Fixes rdar://146459104.
---
 lib/Parse/ParseExpr.cpp |  4 +++-
 test/Unsafe/safe.swift  | 16 ++++++++++++++++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/lib/Parse/ParseExpr.cpp b/lib/Parse/ParseExpr.cpp
index a87247d5fc333..d3fbc3a614ffc 100644
--- a/lib/Parse/ParseExpr.cpp
+++ b/lib/Parse/ParseExpr.cpp
@@ -441,7 +441,9 @@ ParserResult<Expr> Parser::parseExprSequenceElement(Diag<> message,
         peekToken().isAny(tok::r_paren, tok::r_brace, tok::r_square,
                           tok::equal, tok::colon, tok::comma) ||
         (isExprBasic && peekToken().is(tok::l_brace)) ||
-        peekToken().is(tok::period))) {
+        peekToken().is(tok::period) ||
+        (peekToken().isAny(tok::l_paren, tok::l_square) &&
+         peekToken().getRange().getStart() == Tok.getRange().getEnd()))) {
     Tok.setKind(tok::contextual_keyword);
     SourceLoc unsafeLoc = consumeToken();
     ParserResult<Expr> sub =
diff --git a/test/Unsafe/safe.swift b/test/Unsafe/safe.swift
index 299e8e199dd37..e2e80ccd00c8f 100644
--- a/test/Unsafe/safe.swift
+++ b/test/Unsafe/safe.swift
@@ -183,6 +183,8 @@ func acceptBools(_: Bool, _: Bool) { }
 
 func acceptBoolsUnsafeLabel(unsafe _: Bool, _: Bool) { }
 
+func unsafe(_: Int) { }
+
 func unsafeFun() {
   var unsafe = true
   unsafe = false
@@ -200,6 +202,20 @@ func unsafeFun() {
   if unsafe { }
 }
 
+func moreUnsafeFunc(unsafe: [Int]) {
+  let _: [Int] = unsafe []
+  // expected-warning@-1{{no unsafe operations occur within 'unsafe' expression}}
+
+  _ = unsafe[1]
+}
+
+func yetMoreUnsafeFunc(unsafe: () -> Void) {
+  unsafe()
+
+  _ = unsafe ()
+  // expected-warning@-1{{no unsafe operations occur within 'unsafe' expression}}
+}
+
 // @safe suppresses unsafe-type-related diagnostics on an entity
 struct MyArray<Element> {
   @safe func withUnsafeBufferPointer<R, E>(