Function inlining

Hi SPOON contributors. How can I make inline of the function?

I found a way to search for the folllowing data (so, I can find all those objects via your framework):

CtMethod targetMethodDeclaration;
CtMethod extractedMethodDeclaration;
CtInvocation invocation;
Launcher launcher

It will look like:

```
class Test {
void targetMethodDeclaration() {
int e = 5;
int res = extractedMethodDeclaration(e);
return res;
}

int extractedMethodDeclaration(int b) {
int a = 0;
++a;
return a;
}
}
```

Is it possible to inline extractedMethodDeclaration into targetMethodDeclaration:

```
class Test {
void targetMethodDeclaration() {
int e = 0;
int a = 0;
++a;
int res = a;
return res ;
}

void extractedMethodDeclaration() {
int a = 0;
++a;
return a;
}
}
```

Or at least can I inline it with void function? Then I can add functionlity which can insert function with return types.

I see that I can add statements, but I can't apply the changes. Also, it is possible to apply changes on the cloned model, but in different places to get different Java files?

```
public class InlineOpportunity {
protected final CtModel astTree;
private CtMethod targetMethodDeclaration;
private CtMethod extractedMethodDeclaration;
private CtInvocation invocation;

...
}
```

Suppose I have 1 model and all methods (actually, each opportunity has a link to a single model):

```
for (InlineOpportunity opp: opportunities) {
// Do i need to copy it? How can i Do it?
// CtPackage cloneOfAstTree = opp.getAstTree().getRootPackage().clone();

CtBlock block = opp.getTargetMethodDeclaration().getBody();
int counter = 1;
int statementsSize = block.getStatements().size();
for (CtStatement st : block.getStatements()) {
while ((st != opp.getInvocation()) && (counter < statementsSize)) {
++counter;
}
if (counter == statementsSize) {
break;
}
CtBlock block_to_insert = opp.getExtractedMethodDeclaration().getBody();
for (CtStatement inserted_st: block_to_insert.getStatements()) {
st.insertAfter(inserted_st);
}
st.delete(); // If I look at opp.getTargetMethodDeclaration().getBody line, i see that change have been made
String s = opp.getAstTree().getRootPackage().getOriginalSourceFragment().getSourceCode(); // Here I see that the changes are not applied for the whole model (class)
break;
}
}
```

How can I apply chages? How can I make a clone of a model to apply different changes (I have lots of invocations)? I need to save them into a different file.

_Originally posted by @lyriccoder in https://github.com/INRIA/spoon/issues/3251#issuecomment-784334568_

Start with the Spoon entry points named in the report: Launcher, CtModel, CtMethod, CtInvocation, CtBlock, and CtPackage.clone(). Trace how model mutations are printed or persisted instead of relying on getOriginalSourceFragment(). Done would require a defined approach for inlining return-valued and void methods, cloning models, and saving independent transformed Java files.

Written by the indexing model from the issue text.