Source sweep: Use cmStrCat for string concatenation

This patch is generated by a python script that uses regular expressions to
search for string concatenation patterns of the kind

```
std::string str = <ARG0>;
str += <ARG1>;
str += <ARG2>;
...
```

and replaces them with a single `cmStrCat` call

```
std::string str = cmStrCat(<ARG0>, <ARG1>, <ARG2>, ...);
```

If any `<ARGX>` is itself a concatenated string of the kind

```
a + b + c + ...;
```

then `<ARGX>` is split into multiple arguments for the `cmStrCat` call.

If there's a sequence of literals in the `<ARGX>`, then all literals in the
sequence are concatenated and merged into a single literal argument for
the `cmStrCat` call.

Single character strings are converted to single char arguments for
the `cmStrCat` call.

`std::to_string(...)` wrappings are removed from `cmStrCat` arguments,
because it supports numeric types as well as string types.

`arg.substr(x)` arguments to `cmStrCat` are replaced with
`cm::string_view(arg).substr(x)`

1 files changed, 6 insertions, 7 deletions

diff --git a/Source/cmProjectCommand.cxx b/Source/cmProjectCommand.cxx
index 96d9843..f8c5ada 100644
--- a/Source/cmProjectCommand.cxx
+++ b/Source/cmProjectCommand.cxx
@@ -102,11 +102,10 @@ bool cmProjectCommand::InitialPass(std::vector<std::string> const& args,
       }
       doing = DoingLanguages;
       if (!languages.empty()) {
-        std::string msg =
+        std::string msg = cmStrCat(
           "the following parameters must be specified after LANGUAGES "
-          "keyword: ";
-        msg += cmJoin(languages, ", ");
-        msg += '.';
+          "keyword: ",
+          cmJoin(languages, ", "), '.');
         this->Makefile->IssueMessage(MessageType::WARNING, msg);
       }
     } else if (args[i] == "VERSION") {
@@ -368,9 +367,9 @@ bool cmProjectCommand::IncludeByVariable(const std::string& variable)
     return true;
   }
 
-  std::string m = "could not find file:\n"
-                  "  ";
-  m += include;
+  std::string m = cmStrCat("could not find file:\n"
+                           "  ",
+                           include);
   this->SetError(m);
   return false;
 }