From: Richard Trieu <rtrieu@google.com>
Date: Fri, 11 Oct 2013 22:16:04 +0000 (+0000)
Subject: Improve the error message for attempting to build a for range loop using a
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=f18e6e87c2fa41c2a891463483603d770a1e58a7;p=clang

Improve the error message for attempting to build a for range loop using a
function parameter that has array type.  Such a parameter will be treated as
a pointer type instead, resulting in a missing begin function error is a
suggestion to dereference the pointer.  This provides a different,
more informative diagnostic as well as point to the parameter declaration.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@192512 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index 1af7686462..5980f2ce57 100644
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/include/clang/Basic/DiagnosticSemaKinds.td
@@ -1623,6 +1623,9 @@ def note_in_for_range: Note<
 def err_for_range_invalid: Error<
   "invalid range expression of type %0; no viable '%select{begin|end}1' "
   "function available">;
+def err_range_on_array_parameter : Error<
+  "cannot build range expression with array function parameter %0 since "
+  "parameter with array type %1 is treated as pointer type %2">;
 def err_for_range_dereference : Error<
   "invalid range expression of type %0; did you mean to dereference it "
   "with '*'?">;
diff --git a/lib/Sema/SemaStmt.cpp b/lib/Sema/SemaStmt.cpp
index 2977404445..9bd8678c87 100644
--- a/lib/Sema/SemaStmt.cpp
+++ b/lib/Sema/SemaStmt.cpp
@@ -2131,10 +2131,25 @@ Sema::BuildCXXForRangeStmt(SourceLocation ForLoc, SourceLocation ColonLoc,
                                 BeginVar, EndVar, ColonLoc, &CandidateSet,
                                 &BeginExpr, &EndExpr, &BEFFailure);
 
-      // If building the range failed, try dereferencing the range expression
-      // unless a diagnostic was issued or the end function is problematic.
       if (Kind == BFRK_Build && RangeStatus == FRS_NoViableFunction &&
           BEFFailure == BEF_begin) {
+        // If the range is being built from an array parameter, emit a
+        // a diagnostic that it is being treated as a pointer.
+        if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Range)) {
+          if (ParmVarDecl *PVD = dyn_cast<ParmVarDecl>(DRE->getDecl())) {
+            QualType ArrayTy = PVD->getOriginalType();
+            QualType PointerTy = PVD->getType();
+            if (PointerTy->isPointerType() && ArrayTy->isArrayType()) {
+              Diag(Range->getLocStart(), diag::err_range_on_array_parameter)
+                << RangeLoc << PVD << ArrayTy << PointerTy;
+              Diag(PVD->getLocation(), diag::note_declared_at);
+              return StmtError();
+            }
+          }
+        }
+
+        // If building the range failed, try dereferencing the range expression
+        // unless a diagnostic was issued or the end function is problematic.
         StmtResult SR = RebuildForRangeWithDereference(*this, S, ForLoc,
                                                        LoopVarDecl, ColonLoc,
                                                        Range, RangeLoc,
diff --git a/test/SemaCXX/for-range-examples.cpp b/test/SemaCXX/for-range-examples.cpp
index 08c6936816..b3cf9c3264 100644
--- a/test/SemaCXX/for-range-examples.cpp
+++ b/test/SemaCXX/for-range-examples.cpp
@@ -191,3 +191,21 @@ namespace test5 {
       x->foo();
   }
 }
+
+namespace test6 {
+  void foo(int arr[]) {  // expected-note {{declared here}}
+    for (auto i : arr) { }
+      // expected-error@-1 {{cannot build range expression with array function parameter 'arr' since parameter with array type 'int []' is treated as pointer type 'int *'}}
+  }
+
+  struct vector {
+    int *begin() { return 0; }
+    int *end() { return 0; }
+  };
+
+  void foo(vector arr[]) {  // expected-note {{declared here}}
+    // Don't suggest to dereference arr.
+    for (auto i : arr) { }
+      // expected-error@-1 {{cannot build range expression with array function parameter 'arr' since parameter with array type 'test6::vector []' is treated as pointer type 'test6::vector *'}}
+  }
+}