dmd.dfa.fast.structure

struct DFACommon;

The central context for a DFA run.

This structure manages the memory allocator, holds references to global variables (like return values), and tracks the current scope being analyzed.

Performance Note: It uses a custom DFAAllocator (bump-pointer allocator) to avoid the overhead of the GC or standard malloc for the thousands of tiny nodes created during analysis.

struct DFAVar;

Represents the identity of a variable being tracked.

This does NOT store the current value of the variable (that changes depending on where you are in the code). Instead, it stores immutable properties like:

• Is it a boolean? (isBoolean)
• Can it be null? (isNullable)
• Is it a reference to another variable? (base1, indexVar)

Think of this as the "Key" in a map, where the "Value" is the DFALattice.

void walkRoots(scope void delegate(DFAVar* var) del);

Finds the root variables for this one, where base1 is null

void walkToRoot(scope void delegate(DFAVar* var) del);

Walk all variables that end up at a root

void visitFirstBase(scope void delegate(DFAVar* var) del);

Visit the base1 and base2 if present

void visitIfReferenceToAnotherVar(scope void delegate(DFAVar* var) del);

If this variable is a reference to another variable, visit the base variable.

void visitReferenceToAnotherVar(scope void delegate(DFAVar* var) hasIndirection, scope void delegate(DFAVar* var) noIndirection = null);

If this variable is a reference to another, takes into account dereferencing.

void visitIfReadOfReferenceToAnotherVar(scope void delegate(DFAVar* var) resolvedIndirection);

If this variable is a reference to another, takes into account dereferencing.

struct DFAScope;

Represents a specific region of code execution (a scope).

As the DFA walks through the code, it pushes and pops scopes. Each scope holds a table (buckets) of the current state of variables within that block.

When the analysis branches (e.g., inside an if), a new child scope is created to track the state changes specific to that branch.

struct DFALattice;

The collection of values and facts known about a variable.

A DFALattice contains one or more DFAConsequence nodes. Each DFAConsequence represents the state of a variable at the current point in time.

void walkMaybeTops(scope bool delegate(DFAConsequence*) del);

DFAConsequence.maybeTopSeen will be set on the DFAConsequence if it was visited

void cleanupConstant(DFAVar* contextVar);

Remove constant if not context

struct DFAConsequence;

A specific fact known about a variable at the current point in time.

Examples of consequences:

• "This variable is definitely not null" (nullable == NonNull)
• "This variable is True" (truthiness == True)
• "This variable has the integer value 5" (pa - Point Analysis)