[flang] Allow Fortran comments after #include path

[klausler]

Summary

C-style /*comments*/ are removed during preprocessing directive
tokenization, but Fortran !comments need to be specifically
allowed.

Fixes LLVM bugzilla 47466.

[PeteSteinfeld]

All builds, tests, and looks good.

flang/lib/Parser/preprocessor.cpp

void Preprocessor::Directive(const TokenSequence &dir, Prescanner *prescanner) {
   } else if (dirName == "include") {
     if (j == tokens) {
       prescanner->Say(
           dir.GetIntervalProvenanceRange(dirOffset, tokens - dirOffset),
           "#include: missing name of file to include"_err_en_US);
       return;
     }
     std::string include;
-    if (dir.TokenAt(j).ToString() == "<") {
+    if (dir.TokenAt(j).ToString() == "<") { // #include <foo>
       std::size_t k{j + 1};
       if (k >= tokens) {
         prescanner->Say(dir.GetIntervalProvenanceRange(j, tokens - j),
             "#include: file name missing"_err_en_US);
         return;
       }
       while (k < tokens && dir.TokenAt(k) != ">") {
         ++k;
       }
       if (k >= tokens) {
         prescanner->Say(dir.GetIntervalProvenanceRange(j, tokens - j),
             "#include: expected '>' at end of included file"_en_US);
-      } else if (k + 1 < tokens) {
-        prescanner->Say(dir.GetIntervalProvenanceRange(k + 1, tokens - k - 1),
-            "#include: extra stuff ignored after '>'"_en_US);
       }
       TokenSequence braced{dir, j + 1, k - j - 1};
       include = ReplaceMacros(braced, *prescanner).ToString();
-    } else if (j + 1 == tokens &&
-        (include = dir.TokenAt(j).ToString()).substr(0, 1) == "\"" &&
-        include.substr(include.size() - 1, 1) == "\"") {
+      j = k;
+    } else if ((include = dir.TokenAt(j).ToString()).substr(0, 1) == "\"" &&
+        include.substr(include.size() - 1, 1) == "\"") { // #include "foo"
       include = include.substr(1, include.size() - 2);
     } else {
       prescanner->Say(dir.GetTokenProvenanceRange(j < tokens ? j : tokens - 1),
           "#include: expected name of file to include"_err_en_US);
       return;
     }
     if (include.empty()) {
       prescanner->Say(dir.GetTokenProvenanceRange(dirOffset),
           "#include: empty include file name"_err_en_US);
       return;
     }
+    j = dir.SkipBlanks(j + 1);
+    if (j < tokens && dir.TokenAt(j).ToString() != "!") {
+      prescanner->Say(dir.GetIntervalProvenanceRange(j, tokens - j),
+          "#include: extra stuff ignored after file name"_en_US);
+    }
     std::string buf;
     llvm::raw_string_ostream error{buf};
     const SourceFile *included{allSources_.Open(include, error)};
     if (!included) {
       prescanner->Say(dir.GetTokenProvenanceRange(dirOffset),
           "#include: %s"_err_en_US, error.str());
     } else if (included->bytes() > 0) {
       ProvenanceRange fileRange{

flang/test/Preprocessing/include-comment.F90

+! RUN: %f18 -I%S -E %s 2>&1 | FileCheck %s
+! CHECK-NOT: :3:
+#include <empty.h> ! comment
+! CHECK-NOT: :5:
+#include <empty.h> /* comment */
+! CHECK-NOT: :7:
+#include <empty.h> !comment
+! CHECK: :9:20: #include: extra stuff ignored after file name
+#include <empty.h> comment
+! CHECK-NOT: :11:
+#include "empty.h" ! comment
+! CHECK-NOT: :13:
+#include "empty.h" /* comment */
+! CHECK-NOT: :15:
+#include "empty.h" !comment
+! CHECK: :17:20: #include: extra stuff ignored after file name
+#include "empty.h" comment
+end