This happens because of the following from the setResolveBindings docs: Binding information is obtained from the Java model. This means that the compilation unit must be located relative to the Java model. This happens automatically when the source code comes from either setSource(ICompilationUnit) or setSource(IClassFile). When source is supplied by setSource(char[]), the location must be … Read more
Note: In this answer I will use the dyn Trait syntax to make it more clear when a type is a trait object. The older way to write Rc<dyn Trait> is Rc<Trait>. See What does “dyn” mean in a type? No, you can’t downcast Rc<dyn Trait> to Rc<Concrete>, because trait objects like dyn Trait don’t … Read more
ast.visit — unless you override it in a subclass, of course — when called to visit an ast.Node of class foo, calls self.visit_foo if that method exists, otherwise self.generic_visit. The latter, again in its implementation in class ast itself, just calls self.visit on every child node (and performs no other action). So, consider, for example: … Read more
ANTLR 4 produces parse trees based on the grammar instead of ASTs based on arbitrary AST operators and/or rewrite rules. This allows ANTLR 4 to automatically produce listener and visitor interfaces that you can implement in the code using your grammar. The change can be dramatic for users upgrading existing applications from version 3, but … Read more
1.You can take a look at AST explorer. An online tool to explore the ASTs generated by more than 10 parsers. It is a good tool to learn AST tree of a language. AST explorer source at Github.com. 2.Also you can paste your js code into JavaScript AST visualizer and click “show ast” button, you … Read more
This is based on the Expression Evaluator grammar by Terrence Parr. The grammar for this example: grammar Expr002; options { output=AST; ASTLabelType=CommonTree; // type of $stat.tree ref etc… } prog : ( stat )+ ; stat : expr NEWLINE -> expr | ID ‘=’ expr NEWLINE -> ^(‘=’ ID expr) | NEWLINE -> ; expr … Read more
ast.literal_eval() accepts + in the evaluated data because 5+2j (complex number*) are valid literals. The same applies to -. To keep the code simple, no attempt is made to exclude + or – as a binary operators. No other operators are allowed; the function is supposed to only accept literals, not expressions. In other words, … Read more
The documentation states it is safe, and there is no bug relative to security of literal_eval in the bug tracker, so you can probably assume it is safe. Also, according to the source, literal_eval parses the string to a python AST (source tree), and returns only if it is a literal. The code is never … Read more
The fundamental trick is to recognize that parsing, however accomplished, happens in incremental steps, including the reading of the tokens one by one. At each incremental step, there is an opportunity to build part of the AST by combining AST fragments built by other incremental steps. This is a recursive idea, and it bottoms out … Read more
ast.literal_eval (located in ast.py) parses the tree with ast.parse first, then it evaluates the code with quite an ugly recursive function, interpreting the parse tree elements and replacing them with their literal equivalents. Unfortunately the code is not at all expandable, so to add Decimal to the code you need to copy all the code … Read more