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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.

llvm-svn: 192512
This commit is contained in:
Richard Trieu 2013-10-11 22:16:04 +00:00
parent 98f134835f
commit 0825469126
3 changed files with 38 additions and 2 deletions
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3
clang/include/clang/Basic/DiagnosticSemaKinds.td
View File

@ -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 '*'?">;

19
clang/lib/Sema/SemaStmt.cpp
View File

@ -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,

18
clang/test/SemaCXX/for-range-examples.cpp
View File

@ -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 *'}}
}
}