[llvm-branch-commits] [clang] release/19.x: [ObjC] Name lookup in methods shouldn't allow shadowing types (#116683) (PR #116863)

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https://github.com/AreaZR updated https://github.com/llvm/llvm-project/pull/116863

>From 7df6033013ab2c72c396a38db02e30db2cafe075 Mon Sep 17 00:00:00 2001
From: Rose <gfunni234 at gmail.com>
Date: Tue, 19 Nov 2024 14:50:47 -0500
Subject: [PATCH] [ObjC] Name lookup in methods shouldn't allow shadowing types
 (#116683)

Arguably as a bug, Clang has previously not mixed up Objective-C
parameter names with types. This allows developers to write parameter
names that _should_ shadow type names, but don't. For instance:

    @interface Foo
    -(void)foo:(int)id bar:(id)name; // OK
    @end

Commit 97788089988a2ace63d717cadbcfe3443f380f9c changed the way that
parameters are parsed to bring it more in line with how C parameters are
parsed, but it breaks the example above. Given an expectation that the
change wouldn't introduce source breaks, this is not something we can go
forward with.

97788089988a2ace63d717cadbcfe3443f380f9c did this so that late-parsed
attributes could reference Objective-C parameters. This change buffers
Objective-C parameter info until after all parameters are parsed and
turns them into parameter declarations before realizing late-parsed
attributes instead.

Radar-ID: 139996306
(cherry picked from commit 8bdf13b11638d2f3e6792a573fc2be830a03790a)
---
 clang/lib/Parse/ParseObjc.cpp               | 11 +++++++++++
 clang/test/SemaObjC/method-param-named-id.m |  7 +++++++
 2 files changed, 18 insertions(+)
 create mode 100644 clang/test/SemaObjC/method-param-named-id.m

diff --git a/clang/lib/Parse/ParseObjc.cpp b/clang/lib/Parse/ParseObjc.cpp
index 6a2088a73c55b9..c0e2834bfb01a9 100644
--- a/clang/lib/Parse/ParseObjc.cpp
+++ b/clang/lib/Parse/ParseObjc.cpp
@@ -1554,6 +1554,17 @@ Decl *Parser::ParseObjCMethodDecl(SourceLocation mLoc,
                                                     nullptr));
   }
 
+  // Turn ArgInfos into parameters. This must happen after parsing all
+  // parameters for bug compatibility with previous versions of Clang. (For
+  // instance, if a method declares a parameter called "id", that parameter must
+  // not shadow the "id" type.)
+  SmallVector<ParmVarDecl *, 12> ObjCParamInfo;
+  for (auto &ArgInfo : ArgInfos) {
+    ParmVarDecl *Param = Actions.ObjC().ActOnMethodParmDeclaration(
+        getCurScope(), ArgInfo, ObjCParamInfo.size(), MethodDefinition);
+    ObjCParamInfo.push_back(Param);
+  }
+
   // FIXME: Add support for optional parameter list...
   // If attributes exist after the method, parse them.
   MaybeParseAttributes(PAKM_CXX11 | (getLangOpts().ObjC ? PAKM_GNU : 0),
diff --git a/clang/test/SemaObjC/method-param-named-id.m b/clang/test/SemaObjC/method-param-named-id.m
new file mode 100644
index 00000000000000..8269c31116c32d
--- /dev/null
+++ b/clang/test/SemaObjC/method-param-named-id.m
@@ -0,0 +1,7 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -Wno-objc-root-class %s
+
+
+ at interface Foo
+-(void)paramNamedID:(int)id usesIDType:(id)notShadowed;
+-(void)paramNamedID:(int)id, id notShadowed; // expected-warning{{use of C-style parameters in Objective-C method declarations is deprecated}}
+ at end