PR3062: statement expressions should be illegal at file scope. I don't

think this has any significant effects at the moment, but it could 
matter if we start constant-folding statement expressions like gcc does.

llvm-svn: 62943

clang/include/clang/Basic/DiagnosticKinds.def

@@ -1301,6 +1301,8 @@ DIAG(ext_typecheck_comparison_of_distinct_pointers, WARNING,
      "comparison of distinct pointer types (%0 and %1)")
 DIAG(err_typecheck_assign_const, ERROR,
      "read-only variable is not assignable")
+DIAG(err_stmtexpr_file_scope, ERROR,
+     "statement expression not allowed at file scope")
 
 DIAG(err_invalid_this_use, ERROR,
      "invalid use of 'this' outside of a nonstatic member function")

clang/lib/Sema/SemaExpr.cpp

@@ -3940,6 +3940,11 @@ Sema::ExprResult Sema::ActOnStmtExpr(SourceLocation LPLoc, StmtTy *substmt,
   assert(SubStmt && isa<CompoundStmt>(SubStmt) && "Invalid action invocation!");
   CompoundStmt *Compound = cast<CompoundStmt>(SubStmt);
 
+  bool isFileScope = getCurFunctionOrMethodDecl() == 0;
+  if (isFileScope) {
+    return Diag(LPLoc, diag::err_stmtexpr_file_scope);
+  }
+
   // FIXME: there are a variety of strange constraints to enforce here, for
   // example, it is not possible to goto into a stmt expression apparently.
   // More semantic analysis is needed.

clang/test/Sema/stmt_exprs.c

@@ -20,3 +20,5 @@ int test5() { return ({L1: L2: L3: 5;}); }
 int test6() { return ({5;}); }
 void test7() { ({5;}); }                   // expected-warning {{expression result unused}}
 
+// PR3062
+int x[({10;})]; // expected-error {{illegal statement expression}}