Table of Contents

5.4.2.21 With Statement

Note

This section describes the implementation of MS-VBAL §5.4.2.21 With Statement.

Syntax

AST node Instruction kind Notes
WithStatementNode With, EndWith The opener's Instruction.End is right past the block, past its EndWith.

With...End With is a block statement (RD-VBAL §3.4.1 Block Statements). Its opener lowers to the InstructionKind With, and its End With to an EndWith whose Matching is the opener (RD-VBAL §3.5.2 Instruction). The EndWith is outside the block: it is reached by running through the block, and a jump out of the block, to the opener's End or beyond, goes past it.

Static Semantics

What a With block is about is an object, a record of a user-defined type, or a Variant: what its .Member references can be members of. Any other value is VBC09378 With object must be user-defined type, Object, or Variant, as MS-VBA has it (recorded in Excel): a variable of an intrinsic type (With n), a literal or an operator's result (With 5, With n + 1), a project, a module or an Enum type (With VBA, With Strings, With Color). With Nothing compiles. The error is reported once: the body is still in a With block, of a target whose type is not known.

Lowering records the enclosing With block on every instruction inside it (RD-VBAL §3.5.3 Lowering Block Statements):

  • Every instruction lexically inside a With block, however deeply nested (through an If or a loop), carries Instruction.EnclosingWith set to that With's opener offset.
  • When lowering leaves a With block, EnclosingWith is restored to its value before the block.
  • EnclosingWith is computed once, at lowering time. It is not tracked as a runtime stack the interpreter pushes and pops.

Because EnclosingWith is static, a GoTo into or out of a With block leaves no stale state to unwind (RD-VBAL §5.4.2.12 GoTo Statement).

Runtime Semantics

The executor runs the With instruction as follows:

  1. The header expression (the target) is evaluated once.
  2. The target is Set-coerced or Let-coerced:
  3. The result is stored on the activation, keyed by the With instruction's own offset, and an object is held: counted as a reference until the EndWith.
  4. Execution falls through into the body.

The EndWith forgets the stored target and lets go of the object, which then terminates if nothing else holds it.

Every Simple and ConditionalBranch instruction's RuntimeEvaluationContext is recomputed before each dispatch, from Instruction.EnclosingWith (RD-VBAL §3.5.4 Execution). A .Member or !member with-expression then resolves against the innermost enclosing With's stored target, however control reached the instruction, including via GoTo (RD-VBAL §5.6.15 With Expressions).

The block variable

MS-VBAL §5.4.2.21 says that a target "classified as a variable" is the With block variable, and that any other target is held by an anonymous one. MS-VBA, which RD-VBA follows, does this for a record only: a record variable is the block variable, and the block writes its fields where they are. A target that is an object is held, whether a variable names it or not. The block reads the object the variable held when the With statement ran, whatever the block assigns to the variable afterwards, and the object lives until End With:

Set Kept = New Widget
With Kept
    Set Kept = Nothing   ' the block still holds the Widget
    Debug.Print .Hello   ' works: Err.Number is 0
End With                 ' the Widget terminates here

The block holds its object from its With statement to its End With, wherever the program goes in between:

How the program reaches an instruction of the block .Member
By running through its With statement. The object.
A GoTo out of the block and back in, or an error handler and Resume Next back in. The object, still held.
A GoTo into the block, past its With statement. Runtime error 91, Object variable or With block variable not set.
Resume Next past a With statement whose target raised an error: the body runs. Runtime error 91.
A GoTo back into the block after its End With ran. Runtime error 91.

Implementation

  • RDCore.Runtime.Execution.ProcedureExecutor dispatches With instructions.
  • RDCore.Runtime.Semantics.Statements.WithStatementRuntimeSemantics performs the Set-coercion or Let-coercion of step 2.
  • The target is stored through CallStackFrame.SetBlockState and read back through ICallStackFrame.TryGetBlockState, keyed by the opener's offset. Select Case stores its selector the same way (RD-VBAL §5.4.2.10 Select Case Statement); a single block-state value is enough for either.
  • RuntimeExpressionEvaluator resolves the with-expression target through its EnclosingWithTarget resolution.

⏮️ RD-VBAL §5.4.2.20 RaiseEvent Statement | ⏭️ RD-VBAL §5.4.2.22 End Statement

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