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, 8 deletions

diff --git a/Source/cmListCommand.cxx b/Source/cmListCommand.cxx
index 3c41f4a..fe77b33 100644
--- a/Source/cmListCommand.cxx
+++ b/Source/cmListCommand.cxx
@@ -179,10 +179,9 @@ bool GetList(std::vector<std::string>& list, const std::string& var,
       // empty values
       list.clear();
       cmExpandList(listString, list);
-      std::string warn = cmPolicies::GetPolicyWarning(cmPolicies::CMP0007);
-      warn += " List has value = [";
-      warn += listString;
-      warn += "].";
+      std::string warn =
+        cmStrCat(cmPolicies::GetPolicyWarning(cmPolicies::CMP0007),
+                 " List has value = [", listString, "].");
       makefile.IssueMessage(MessageType::AUTHOR_WARNING, warn);
       return true;
     }
@@ -1549,10 +1548,9 @@ bool FilterRegex(std::vector<std::string> const& args, bool includeMatches,
   const std::string& pattern = args[4];
   cmsys::RegularExpression regex(pattern);
   if (!regex.is_valid()) {
-    std::string error = "sub-command FILTER, mode REGEX ";
-    error += "failed to compile regex \"";
-    error += pattern;
-    error += "\".";
+    std::string error =
+      cmStrCat("sub-command FILTER, mode REGEX failed to compile regex \"",
+               pattern, "\".");
     status.SetError(error);
     return false;
   }