1.1.3 Core Semantic Flags
The language core features an analytical pipeline that attaches detailed semantic flags to abstract syntax tree (AST) nodes. ComparisonOperatorSemanticFlags is an example of core semantic flags. The pipeline is described in RD-VBAL §5.0 Semantics.
Core semantic flags are spec-driven. They are designed to describe the semantic reality of an operation, without any restraint or judgement: semantic flags are pure facts, not opinions.
A semantic flag typically exists because the specified semantics contain a branch or condition:
| Specified semantics | Semantic flag |
|---|---|
| The effective type of an operation evaluates a VBNullType differently than a VBNumericType. | The semantic flags for that operation should reflect the NullEffectiveType flag. |
The specifications mention a NaN operand. |
There should be a HasNaNOperand semantic flag. |
👉 Do create new core semantic flags as needed to accurately reflect the semantic reality of an operation.
❌ Do not create new core semantic flags that no specified (RD-VBAL) semantics justify.
Extensions
🧩 Extensions can, and should, enrich a semantic context well beyond the responsibilities of the language core. They do so with diagnostics issued by analyzers that can inspect the complete semantic reality of the application.
Semantic flags aim to expose all the facts of the application's semantic reality. Diagnostics are described in RD-VBAL §1.1.4 Core Diagnostics.
Semantic Flags Specified Elsewhere
| Condition | Semantic flag | See |
|---|---|---|
A project reference shadows a VBA library definition. |
The shadowing should be detected in the semantic layer and reported through semantic flags, so that RDCore.Diagnostics can issue shadowed declaration diagnostics. | RD-VBAL §2.3.1.3 Name Resolution |
An implicit ReDim declaration. |
A later analysis pass raises a semantic flag at the site. | RD-VBAL §5.4.3.3 ReDim Statement |
A deferred parameter inferred as Variant, from array or heterogeneous arguments. |
Should issue semantic flags as appropriate, to signal the case to any listening language-level extensions. | RD-VBAL §2.4.4 Deferred Types |
| A predeclared class module. | Semantic flags should identify whether the module is stateful or not. | RD-VBAL §3.1.1 Attributes |
⏮️ RD-VBAL §1.1.2 Language Core Extensions | ⏭️ RD-VBAL §1.1.4 Core Diagnostics