There was one announce about C# tool to see ASTs and Alexandre Bergel shows that within minutes you could get the same in Pharo with roassal :). Here is what he is saying:
I am not sure to what syntax visualization is useful for, but indeed, this is easy in Roassal. Assuming a class MyVisitor, that simples collect the nodes of the AST.
“We get the nodes from the AST”
ast := RBParser parseMethod: (ArrayTest>>#testReplaceFromToWithStartingAt) getSource.
visitor := MyVisitor new.
ast acceptVisitor: visitor.”Visualization”
g := RTGraphBuilder new.
if: #isMessage shape: (RTEllipse new size: 10; color: Color red ) + (RTLabel new text: #selector);
if: #isReturn shape: (RTEllipse new size: 10; color: Color red );
if: #isBlock shape: (RTBox new size: 10; color: Color blue );
shape: (RTEllipse new size: 10; color: Color gray ).
g layout use: RTTreeLayout new.
g edge connectTo: #parent.g addAll: visitor nodes.