[flang] Improve module file error message wording (#122787)

Instead of "Cannot read ...", distinguish true errors in finding and
parsing module files from problems with unexpected hash codes by using
"Cannot parse" or "Cannot use" wording as appropriate.

flang/lib/Semantics/mod-file.cpp

@@ -139,7 +139,7 @@ void ModFileWriter::Write(const Symbol &symbol) {
   const auto *ancestor{module.ancestor()};
   isSubmodule_ = ancestor != nullptr;
   auto ancestorName{ancestor ? ancestor->GetName().value().ToString() : ""s};
-  auto path{context_.moduleDirectory() + '/' +
+  std::string path{context_.moduleDirectory() + '/' +
       ModFileName(symbol.name(), ancestorName, context_.moduleFileSuffix())};
 
   UnorderedSymbolSet hermeticModules;
@@ -1392,7 +1392,8 @@ Scope *ModFileReader::Read(SourceName name, std::optional<bool> isIntrinsic,
     // USE, NON_INTRINSIC global name isn't a module?
     fatalError = isIntrinsic.has_value();
   }
-  auto path{ModFileName(name, ancestorName, context_.moduleFileSuffix())};
+  std::string path{
+      ModFileName(name, ancestorName, context_.moduleFileSuffix())};
   parser::Parsing parsing{context_.allCookedSources()};
   parser::Options options;
   options.isModuleFile = true;
@@ -1468,7 +1469,7 @@ Scope *ModFileReader::Read(SourceName name, std::optional<bool> isIntrinsic,
       } else {
         for (auto &msg : parsing.messages().messages()) {
           std::string str{msg.ToString()};
-          Say(name, ancestorName,
+          Say("parse", name, ancestorName,
               parser::MessageFixedText{str.c_str(), str.size(), msg.severity()},
               path);
         }
@@ -1480,11 +1481,11 @@ Scope *ModFileReader::Read(SourceName name, std::optional<bool> isIntrinsic,
   std::optional<ModuleCheckSumType> checkSum{
       VerifyHeader(sourceFile->content())};
   if (!checkSum) {
-    Say(name, ancestorName, "File has invalid checksum: %s"_err_en_US,
+    Say("use", name, ancestorName, "File has invalid checksum: %s"_err_en_US,
         sourceFile->path());
     return nullptr;
   } else if (requiredHash && *requiredHash != *checkSum) {
-    Say(name, ancestorName,
+    Say("use", name, ancestorName,
         "File is not the right module file for %s"_err_en_US,
         "'"s + name.ToString() + "': "s + sourceFile->path());
     return nullptr;
@@ -1494,7 +1495,7 @@ Scope *ModFileReader::Read(SourceName name, std::optional<bool> isIntrinsic,
   std::optional<parser::Program> &parsedProgram{parsing.parseTree()};
   if (!parsing.messages().empty() || !parsing.consumedWholeFile() ||
       !parsedProgram) {
-    Say(name, ancestorName, "Module file is corrupt: %s"_err_en_US,
+    Say("parse", name, ancestorName, "Module file is corrupt: %s"_err_en_US,
         sourceFile->path());
     return nullptr;
   }
@@ -1572,10 +1573,10 @@ Scope *ModFileReader::Read(SourceName name, std::optional<bool> isIntrinsic,
   }
 }
 
-parser::Message &ModFileReader::Say(SourceName name,
+parser::Message &ModFileReader::Say(const char *verb, SourceName name,
     const std::string &ancestor, parser::MessageFixedText &&msg,
     const std::string &arg) {
-  return context_.Say(name, "Cannot read module file for %s: %s"_err_en_US,
+  return context_.Say(name, "Cannot %s module file for %s: %s"_err_en_US, verb,
       parser::MessageFormattedText{ancestor.empty()
               ? "module '%s'"_en_US
               : "submodule '%s' of module '%s'"_en_US,

flang/lib/Semantics/mod-file.h

@@ -102,7 +102,7 @@ public:
 private:
   SemanticsContext &context_;
 
-  parser::Message &Say(SourceName, const std::string &,
+  parser::Message &Say(const char *verb, SourceName, const std::string &,
       parser::MessageFixedText &&, const std::string &);
 };
 

flang/test/Driver/intrinsic-module-path.f90

@@ -12,8 +12,8 @@
 ! WITHOUT-NOT: 'ieee_arithmetic.mod' was not found
 ! WITHOUT-NOT: 'iso_fortran_env.mod' was not found
 
-! GIVEN: error: Cannot read module file for module 'ieee_arithmetic': File has invalid checksum
-! GIVEN: error: Cannot read module file for module 'iso_fortran_env': File has invalid checksum
+! GIVEN: error: Cannot use module file for module 'ieee_arithmetic': File has invalid checksum
+! GIVEN: error: Cannot use module file for module 'iso_fortran_env': File has invalid checksum
 
 
 program test_intrinsic_module_path

flang/test/Driver/use-module.f90

@@ -32,14 +32,14 @@
 
 ! INCLUDED-NOT: error
 
-! MISSING_MOD2-NOT:error: Cannot read module file for module 'basictestmoduleone''
+! MISSING_MOD2-NOT:error: Cannot parse module file for module 'basictestmoduleone''
 ! MISSING_MOD2-NOT:error: Derived type 't1' not found
-! MISSING_MOD2:error: Cannot read module file for module 'basictestmoduletwo'
+! MISSING_MOD2:error: Cannot parse module file for module 'basictestmoduletwo'
 ! MISSING_MOD2:error: Derived type 't2' not found
 
-! SINGLEINCLUDE-NOT:error: Cannot read module file for module 'basictestmoduleone'
+! SINGLEINCLUDE-NOT:error: Cannot parse module file for module 'basictestmoduleone'
 ! SINGLEINCLUDE:error: Derived type 't1' not found
-! SINGLEINCLUDE-NOT:error: Cannot read module file for module 'basictestmoduletwo'
+! SINGLEINCLUDE-NOT:error: Cannot parse module file for module 'basictestmoduletwo'
 ! SINGLEINCLUDE-NOT:error: Derived type 't2' not found
 
 

flang/test/Semantics/modfile43.f90

@@ -18,13 +18,13 @@ module m4
   use :: iso_fortran_env, only: user_defined_123
 end module
 module m5
-  !ERROR: Cannot read module file for module 'ieee_arithmetic': Source file 'ieee_arithmetic.mod' was not found
+  !ERROR: Cannot parse module file for module 'ieee_arithmetic': Source file 'ieee_arithmetic.mod' was not found
   use, non_intrinsic :: ieee_arithmetic, only: ieee_selected_real_kind
 end module
 module notAnIntrinsicModule
 end module
 module m6
-  !ERROR: Cannot read module file for module 'notanintrinsicmodule': Source file 'notanintrinsicmodule.mod' was not found
+  !ERROR: Cannot parse module file for module 'notanintrinsicmodule': Source file 'notanintrinsicmodule.mod' was not found
   use, intrinsic :: notAnIntrinsicModule
 end module
 

flang/test/Semantics/modfile63.f90

@@ -13,4 +13,4 @@ use modfile63b
 call s2
 end
 
-! ERROR: Cannot read module file for module 'modfile63a': File is not the right module file for 'modfile63a':
+! ERROR: Cannot use module file for module 'modfile63a': File is not the right module file for 'modfile63a':

flang/test/Semantics/modfile70.f90

@@ -2,4 +2,4 @@
 end
 
 ! RUN: not %flang_fc1 -fsyntax-only -J%S/Inputs -w %s 2>&1 | FileCheck --check-prefix=ERROR %s
-! ERROR: Cannot read module file for module 'modfile70': File has invalid checksum:
+! ERROR: Cannot use module file for module 'modfile70': File has invalid checksum:

flang/test/Semantics/resolve12.f90

@@ -6,7 +6,7 @@ subroutine sub
 end
 
 use m1
-!ERROR: Cannot read module file for module 'm2': Source file 'm2.mod' was not found
+!ERROR: Cannot parse module file for module 'm2': Source file 'm2.mod' was not found
 use m2
 !ERROR: 'sub' is not a module
 use sub

flang/test/Semantics/resolve26.f90

@@ -16,10 +16,10 @@ end
 submodule(m1) s1
 end
 
-!ERROR: Cannot read module file for submodule 's1' of module 'm2': Source file 'm2-s1.mod' was not found
+!ERROR: Cannot parse module file for submodule 's1' of module 'm2': Source file 'm2-s1.mod' was not found
 submodule(m2:s1) s2
 end
 
-!ERROR: Cannot read module file for module 'm3': Source file 'm3.mod' was not found
+!ERROR: Cannot parse module file for module 'm3': Source file 'm3.mod' was not found
 submodule(m3:s1) s3
 end