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, 6 deletions

diff --git a/Source/cmVariableRequiresCommand.cxx b/Source/cmVariableRequiresCommand.cxx
index 9878ff1..c44eeca 100644
--- a/Source/cmVariableRequiresCommand.cxx
+++ b/Source/cmVariableRequiresCommand.cxx
@@ -4,6 +4,7 @@
 
 #include "cmMakefile.h"
 #include "cmState.h"
+#include "cmStringAlgorithms.h"
 #include "cmSystemTools.h"
 
 class cmExecutionStatus;
@@ -46,12 +47,11 @@ bool cmVariableRequiresCommand::InitialPass(
   }
 
   if (!requirementsMet) {
-    std::string message = "Variable assertion failed:\n";
-    message +=
-      testVariable + " Requires that the following unset variables are set:\n";
-    message += notSet;
-    message += "\nPlease set them, or set ";
-    message += testVariable + " to false, and re-configure.\n";
+    std::string message =
+      cmStrCat("Variable assertion failed:\n", testVariable,
+               " Requires that the following unset variables are set:\n",
+               notSet, "\nPlease set them, or set ", testVariable,
+               " to false, and re-configure.\n");
     if (hasAdvanced) {
       message +=
         "One or more of the required variables is advanced."