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, 5 insertions, 4 deletions

diff --git a/Source/cmIfCommand.cxx b/Source/cmIfCommand.cxx
index 7b49ae7..f719041 100644
--- a/Source/cmIfCommand.cxx
+++ b/Source/cmIfCommand.cxx
@@ -14,6 +14,7 @@
 #include "cmMakefile.h"
 #include "cmMessageType.h"
 #include "cmOutputConverter.h"
+#include "cmStringAlgorithms.h"
 #include "cmSystemTools.h"
 #include "cmake.h"
 
@@ -127,8 +128,8 @@ bool cmIfFunctionBlocker::Replay(std::vector<cmListFileFunction> functions,
           conditionEvaluator.IsTrue(expandedArguments, errorString, messType);
 
         if (!errorString.empty()) {
-          std::string err = cmIfCommandError(expandedArguments);
-          err += errorString;
+          std::string err =
+            cmStrCat(cmIfCommandError(expandedArguments), errorString);
           cmListFileBacktrace bt = mf.GetBacktrace(func);
           mf.GetCMakeInstance()->IssueMessage(messType, err, bt);
           if (messType == MessageType::FATAL_ERROR) {
@@ -184,8 +185,8 @@ bool cmIfCommand(std::vector<cmListFileArgument> const& args,
     conditionEvaluator.IsTrue(expandedArguments, errorString, status);
 
   if (!errorString.empty()) {
-    std::string err = "if " + cmIfCommandError(expandedArguments);
-    err += errorString;
+    std::string err =
+      cmStrCat("if ", cmIfCommandError(expandedArguments), errorString);
     if (status == MessageType::FATAL_ERROR) {
       makefile.IssueMessage(MessageType::FATAL_ERROR, err);
       cmSystemTools::SetFatalErrorOccured();