Validation
The validation module implements the semantic validation step of the compiler. The validator is a hand-written visitor that offers a callback when visiting the single AST-nodes to then perform the different validation tasks.
The validation rules are implemented in dedicated validator-structs:
| Validator | Responsibilities |
|---|---|
| global_validator | Semantic rules on the level of declarations as a whole (e.g. name-conflicts) |
| pou_validator | Semantic rules on the level of programs, function- and function-blocks. |
| recursive_validator | Semantic rules on the level of recursion (e.g. struct referencing itself) |
| stmt_validator | Semantic rules on the level of statements (e.g. invalid type-casts). |
| variable_validator | Semantic rules on the level of variable declarations (e.g. empty var-blocks, empty structs, etc.). |
Diagnostics
Problems (semantic or syntactic) are represented as Diagnostics 1. Diagnostics carry information on the exact location inside the source-string (start- & end-offset), a custom message and a unique error-number to identify the problem.
There are 3 types of Diagnostics:
| Diagnostic | Description |
|---|---|
| SyntaxError | A syntax error is a diagnostic that is created by the parser if it discovers a token-stream that does not match the language's grammar. |
| GeneralError | General errors are problems that occured during the compilation process, that cannot be linked to a malformed input (e.g. file-I/O problems, internal LLVM errors, etc.). |
| Improvement | Problems that may not prevent successful compilation but are still considered a flaw in the source-code. (e.g. use proprietary POINTER TO instead of the norm-compliant REF_TO). |
1
:(i): The diagnostics are subject to change since they don't elegantly represent the different types of problems (e.g. semantic problems).