Table of Contents

5.4.2.8 If Statement

Note

This section describes the implementation of MS-VBAL §5.4.2.8 If Statement.

Syntax

AST node Instruction kind(s) Notes
IfBlockStatementNode ConditionalBranch The If header.
ElseIfBlockStatementNode ConditionalBranch An ElseIf header.
ElseBlockStatementNode — The Else branch needs no condition. The last header's Else offset names the first instruction of its body.
— (synthesized) Jump The trailing jump at the end of each branch's body. Node is null; Target is right past the whole construct.

See RD-VBAL §3.4.1 Block Statements and RD-VBAL §3.5.2 Instruction.

Runtime Semantics

The executor dispatches ConditionalBranch for an If or ElseIf header, or a single-line If (RD-VBAL §5.4.2.9 Single-line If Statement), with a Boolean condition.

  1. Evaluate the header's condition, forced to Boolean by ConditionEvaluator (MS-VBAL §5.5.1.2.2 Let-coercion to and from Boolean).
  2. When the condition is True, fall through into the branch's body.
  3. When the condition is False, go to the header's Else offset: the next header in the chain, the first instruction of the Else body, or right past the whole construct.
  4. After a branch's body runs, the synthesized trailing Jump goes right past the whole construct.

A condition is not coerced through an operator node, because a condition has no operator of its own in source: If x Then let-coerces x without any (...).

Implementation

  • ProcedureExecutor dispatches ConditionalBranch.
  • RDCore.Runtime.Execution.ConditionEvaluator forces the condition to Boolean. It calls VBBooleanLetCoercionRuntimeSemantics directly, rather than through an operator node (RD-VBAL §3.5.4 Execution).
  • An If block needs no synthesized closer: leaving the last branch, or the Else branch, already reaches the offset that the construct's own End/Else chaining designates.
  • After every branch's body, lowering emits a synthesized, unconditional Jump to right past the whole construct, even for the last branch (RD-VBAL §3.5.3 Lowering Block Statements).

⏮️ RD-VBAL §5.4.2.7 Exit Do Statement | ⏭️ RD-VBAL §5.4.2.9 Single-line If Statement

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