[clang] release/19.x: [ObjC] Name lookup in methods shouldn't allow shadowing types (#116683) (PR #116861)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Rose (AreaZR)

<details>
<summary>Changes</summary>

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)

---
Full diff: https://github.com/llvm/llvm-project/pull/116861.diff


2 Files Affected:

- (modified) clang/lib/Parse/ParseObjc.cpp (+13-4) 
- (added) clang/test/SemaObjC/method-param-named-id.m (+7) 


``````````diff
diff --git a/clang/lib/Parse/ParseObjc.cpp b/clang/lib/Parse/ParseObjc.cpp
index e69fa152481982..ddf59bd748f343 100644
--- a/clang/lib/Parse/ParseObjc.cpp
+++ b/clang/lib/Parse/ParseObjc.cpp
@@ -1454,7 +1454,7 @@ Decl *Parser::ParseObjCMethodDecl(SourceLocation mLoc,
 
   SmallVector<const IdentifierInfo *, 12> KeyIdents;
   SmallVector<SourceLocation, 12> KeyLocs;
-  SmallVector<ParmVarDecl *, 12> ObjCParamInfo;
+  SmallVector<SemaObjC::ObjCArgInfo, 12> ArgInfos;
   ParseScope PrototypeScope(this, Scope::FunctionPrototypeScope |
                             Scope::FunctionDeclarationScope | Scope::DeclScope);
 
@@ -1495,9 +1495,7 @@ Decl *Parser::ParseObjCMethodDecl(SourceLocation mLoc,
     ArgInfo.NameLoc = Tok.getLocation();
     ConsumeToken(); // Eat the identifier.
 
-    ParmVarDecl *Param = Actions.ObjC().ActOnMethodParmDeclaration(
-        getCurScope(), ArgInfo, ObjCParamInfo.size(), MethodDefinition);
-    ObjCParamInfo.push_back(Param);
+    ArgInfos.push_back(ArgInfo);
     KeyIdents.push_back(SelIdent);
     KeyLocs.push_back(selLoc);
 
@@ -1557,6 +1555,17 @@ 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

``````````

</details>


https://github.com/llvm/llvm-project/pull/116861