Semantic Analysis

• parsing gives shape; analysis validates meaning
• names, binding kinds, scope, and call legality before runtime

Scope policy

• explicit scope stack: current → parent → root
• duplicate declarations forbidden in same scope
• inner declaration shadows outer

Function strategy

• two-phase often needed: 1) register function declarations 2) validate function bodies
• enables recursion and arity checks at call sites

Assignment rules

• const binding may not be reassigned
• var may be updated in nearest enclosing scope
• unresolved targets are undefined name errors

Control-flow validation

• track inFunctionDepth
• return valid only when inside function

Diagnostic quality

• deterministic issue order
• messages include location + concrete symbol/call count
• examples:
  • undefined name: x
  • redeclare in same scope: x
  • cannot assign to const: pi
  • return outside function
  • arity mismatch: add expects 2, got 1

Why good analysis

• catches failures early
• aligns compiler and VM error model
• keeps runtime traces meaningful

Quick checks

• same-name in one scope -> declare error
• same-name in child scope -> shadow allowed
• recursion accepted after declaration pass
• call arity mismatch flagged before compile emit
• valid call path may still error at runtime if types mismatch