C#: Replace BaseSSA classes with shared code.

[aschackmull]

This aligns the C# BaseSSA classes with the shared SSA signature by using the classes provided by the shared library.

[aschackmull]

Dca is uneventful.

[Copilot]

Pull request overview

Aligns the C# BaseSSA implementation with the shared (language-independent) SSA signature by switching to the shared library’s SSA classes and adapting downstream uses accordingly.

Changes:

• Refactors BaseSSA.qll to implement the shared SSA input/signature and re-export the shared SSA types.
• Updates internal consumers (Dispatch.qll, Steps.qll) to use the new shared SSA class names/types.
• Adjusts the SSA consistency library test to match the new explicit/implicit definition split.

Show a summary per file

File	Description
csharp/ql/test/library-tests/dataflow/ssa/BaseSsaConsistency.ql	Updates the test query to use shared SSA write/parameter-init definition types.
csharp/ql/lib/semmle/code/csharp/dispatch/Dispatch.qll	Switches parameter-entry detection to shared BaseSsa::SsaParameterInit.
csharp/ql/lib/semmle/code/csharp/dataflow/internal/Steps.qll	Updates definition-to-read resolution to use shared SsaDefinition/SsaExplicitWrite.
csharp/ql/lib/semmle/code/csharp/dataflow/internal/BaseSSA.qll	Replaces custom Definition/PhiNode wrappers with shared SSA construction and types.

Copilot's findings

Comments suppressed due to low confidence (1)

csharp/ql/lib/semmle/code/csharp/dataflow/internal/BaseSSA.qll:43

• The comment inside entryDef still describes this as an “implicit entry definition” (and explains implicitEntryDef-style behavior). Since the predicate has been renamed to entryDef and now also seems to be used for parameter initialization, consider updating the wording to match the new terminology to avoid confusion for future maintainers.

      // In case `c` has multiple bodies, we want each body to get its own implicit
      // entry definition. In case `c` doesn't have multiple bodies, the line below
      // is simply the same as `bb = entry`, because `entry.getFirstNode().getASuccessor()`
      // will be in the entry block.
      bb = entry.getFirstNode().getASuccessor().getBasicBlock() and

• Files reviewed: 4/4 changed files
• Comments generated: 0