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/116863.diff


2 Files Affected:

- (modified) clang/lib/Parse/ParseObjc.cpp (+11) 
- (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 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
+
+
+@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}}
+@end

``````````

</details>


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