Polymorphism and Dispatch Semantics: Concept Explained

Concept

In short: Polymorphism in SV means a base handle can point to many derived object types, with behavior decided by virtual dispatch and safe downcast patterns.

A base-class handle referencing derived objects enables generic containers, APIs, and UVM framework flows. This is powerful for writing protocol-agnostic infrastructure: one queue of base handles can schedule many specialized implementations.

Dispatch semantics are strict: virtual methods choose implementation from object type at runtime, while non-virtual methods are selected by handle type. Reliable mental modeling of this split prevents many scoreboard and driver surprises.

Downcasting from base to derived requires runtime type checking with $cast. Safe code checks cast success before using derived-only members; direct assignment without checking risks null handles or simulator fatals depending on context.

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