Fix a few auto-related issues:

 * 'auto' was being rejected on abstract-declarators with trailing return
types and on typedefs with trailing return types. 'auto' is always
allowed in these cases. This was found while testing the fix for PR 9278.

 * A very poor diagnostic was being issued for auto (f() -> int): "return
type must be 'auto', not 'auto'". This is closely related to PR 9060.

 * Trailing return type handling was happening slightly too late,
resulting in the checks for functions returning arrays and functions
returning functions being missed.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@126166 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 44 insertions, 19 deletions

diff --git a/lib/Sema/SemaType.cpp b/lib/Sema/SemaType.cpp
index 8051b56034..9468b9c74a 100644
--- a/lib/Sema/SemaType.cpp
+++ b/lib/Sema/SemaType.cpp
@@ -1450,6 +1450,7 @@ TypeSourceInfo *Sema::GetTypeForDeclarator(Declarator &D, Scope *S,
   if (D.getAttributes())
     distributeTypeAttrsFromDeclarator(state, T);
 
+  // C++0x [dcl.spec.auto]p5: reject 'auto' if it is not in an allowed context.
   if (D.getDeclSpec().getTypeSpecType() == DeclSpec::TST_auto &&
       !D.isFunctionDeclarator()) {
     int Error = -1;
@@ -1495,6 +1496,25 @@ TypeSourceInfo *Sema::GetTypeForDeclarator(Declarator &D, Scope *S,
     if (D.getDeclSpec().getStorageClassSpec() == DeclSpec::SCS_typedef)
       Error = 8;
 
+    // C++0x [dcl.spec.auto]p2: 'auto' is always fine if the declarator
+    // contains a trailing return type. That is only legal at the outermost
+    // level. Check all declarator chunks (outermost first) anyway, to give
+    // better diagnostics.
+    if (Error != -1) {
+      for (unsigned i = 0, e = D.getNumTypeObjects(); i != e; ++i) {
+        unsigned chunkIndex = e - i - 1;
+        state.setCurrentChunkIndex(chunkIndex);
+        DeclaratorChunk &DeclType = D.getTypeObject(chunkIndex);
+        if (DeclType.Kind == DeclaratorChunk::Function) {
+          const DeclaratorChunk::FunctionTypeInfo &FTI = DeclType.Fun;
+          if (FTI.TrailingReturnType) {
+            Error = -1;
+            break;
+          }
+        }
+      }
+    }
+
     if (Error != -1) {
       Diag(D.getDeclSpec().getTypeSpecTypeLoc(), diag::err_auto_not_allowed)
         << Error;
@@ -1502,7 +1522,7 @@ TypeSourceInfo *Sema::GetTypeForDeclarator(Declarator &D, Scope *S,
       D.setInvalidType(true);
     }
   }
-
+  
   if (T.isNull())
     return Context.getNullTypeSourceInfo();
 
@@ -1603,21 +1623,6 @@ TypeSourceInfo *Sema::GetTypeForDeclarator(Declarator &D, Scope *S,
       // of the type, otherwise the argument list is ().
       const DeclaratorChunk::FunctionTypeInfo &FTI = DeclType.Fun;
 
-      // C99 6.7.5.3p1: The return type may not be a function or array type.
-      // For conversion functions, we'll diagnose this particular error later.
-      if ((T->isArrayType() || T->isFunctionType()) &&
-          (D.getName().getKind() != UnqualifiedId::IK_ConversionFunctionId)) {
-        unsigned diagID = diag::err_func_returning_array_function;
-        // Last processing chunk in block context means this function chunk
-        // represents the block.
-        if (chunkIndex == 0 &&
-            D.getContext() == Declarator::BlockLiteralContext)
-          diagID = diag::err_block_returning_array_function;
-        Diag(DeclType.Loc, diagID) << T->isFunctionType() << T;
-        T = Context.IntTy;
-        D.setInvalidType(true);
-      }
-
       // Check for auto functions and trailing return type and adjust the
       // return type accordingly.
       if (!D.isInvalidType()) {
@@ -1630,8 +1635,13 @@ TypeSourceInfo *Sema::GetTypeForDeclarator(Declarator &D, Scope *S,
           T = Context.IntTy;
           D.setInvalidType(true);
         } else if (FTI.TrailingReturnType) {
-          if (T.hasQualifiers() || !isa<AutoType>(T)) {
-            // T must be exactly 'auto' at this point. See CWG issue 681.
+          // T must be exactly 'auto' at this point. See CWG issue 681.
+          if (isa<ParenType>(T)) {
+            Diag(D.getDeclSpec().getTypeSpecTypeLoc(),
+                 diag::err_trailing_return_in_parens)
+              << T << D.getDeclSpec().getSourceRange();
+            D.setInvalidType(true);
+          } else if (T.hasQualifiers() || !isa<AutoType>(T)) {
             Diag(D.getDeclSpec().getTypeSpecTypeLoc(),
                  diag::err_trailing_return_without_auto)
               << T << D.getDeclSpec().getSourceRange();
@@ -1644,6 +1654,21 @@ TypeSourceInfo *Sema::GetTypeForDeclarator(Declarator &D, Scope *S,
         }
       }
 
+      // C99 6.7.5.3p1: The return type may not be a function or array type.
+      // For conversion functions, we'll diagnose this particular error later.
+      if ((T->isArrayType() || T->isFunctionType()) &&
+          (D.getName().getKind() != UnqualifiedId::IK_ConversionFunctionId)) {
+        unsigned diagID = diag::err_func_returning_array_function;
+        // Last processing chunk in block context means this function chunk
+        // represents the block.
+        if (chunkIndex == 0 &&
+            D.getContext() == Declarator::BlockLiteralContext)
+          diagID = diag::err_block_returning_array_function;
+        Diag(DeclType.Loc, diagID) << T->isFunctionType() << T;
+        T = Context.IntTy;
+        D.setInvalidType(true);
+      }
+
       // cv-qualifiers on return types are pointless except when the type is a
       // class type in C++.
       if (T.getCVRQualifiers() && D.getDeclSpec().getTypeQualifiers() &&
@@ -2050,7 +2075,7 @@ TypeSourceInfo *Sema::GetTypeForDeclarator(Declarator &D, Scope *S,
       break;
     }
   }
-  
+
   if (T.isNull())
     return Context.getNullTypeSourceInfo();
   else if (D.isInvalidType())