The C# debug-steps view highlights and centers the exact AST node a
transform changed; the ILAst view already had the step tree and
replay-at-step but produced no highlight. Bring it to parity.
IL rendering has no token-writer seam like the C# output visitor, so
per-instruction text spans are recorded by bracketing
ILInstruction.WriteTo via a new INodeTrackingOutput. The dominant
inst.ReplaceWith(newInst) transform pattern detaches the instruction
passed to Step, so ILTransformContext gains EndStep to record the
produced instruction; Stepper additionally records the position's
ancestor chain as fallback candidates before the step-limit throw, so
the "show state before" view -- which halts at the selected step --
still resolves to a surviving ancestor (ultimately the ILFunction).
The highlight-range resolver is shared with the C# language.
Assisted-by: Claude:claude-opus-4-8:Claude Code
For user-defined increments, there were problems with Roslyn was optimizing out one of the stores.
The new transform FixRemainingIncrements now takes increments/decrements that were not detected by TransformAssignment and introduces a temporary variable that can be incremented.
This sometimes requires un-inlining via the new ILInstruction.Extract() operation.
Extract() is not supported in all possible contexts, so it is possible but unlikely that some op_Increment calls remain.
For decimals, the situation is different: legacy csc actually was optimizing "d + 1m" to "op_Increment(d)", so we can get rid of any left-over increments by undoing this optimization. This now happens in ReplaceMethodCallsWithOperators.
Siegfried Pammer
Peter Crabtree
Daniel Grunwald
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