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The Compiler Shape (without compiler jargon)

This chapter answers: “Who does what?” without requiring prior compiler knowledge.

2.1 The pipeline as promises​

Think of each phase as a team member with a job and a promise:

Lexer​

  • Input: source text
  • Output: tokens (+ location info)
  • Promise: the parser receives a stable token stream

Parser​

  • Input: tokens
  • Output: AST with spans
  • Promise: later phases can walk a structured tree and point diagnostics at precise source ranges

Semantics Phase 1 (symbol collection)​

  • Input: AST
  • Output: symbol table + scopes
  • Promise: name lookup is stable (what value refers to, which inc overload, etc.)

Type resolver​

  • Input: AST + symbol table
  • Output: the same AST, now annotated with TypeInfo
  • Promise: lowering doesn’t guess types — it reads them from the AST

Optional Semantics Phase 2 (extra validation)​

  • Input: typed AST
  • Output: additional checks (often wired through tests)
  • Promise: catches semantic rules that don’t fit nicely into typing

MLIR lowering​

  • Input: typed AST
  • Output: Ora MLIR module
  • Promise: downstream passes/verification operate on a consistent IR

Verification & passes​

  • Input: Ora MLIR
  • Output: verified, optimized IR; optionally SMT results
  • Promise: invalid programs are rejected early; valid programs are normalized for the backend

Ora → SIR conversion​

  • Input: Ora MLIR
  • Output: SIR MLIR
  • Promise: whatever reaches SIR is in the “legal” subset supported by the backend

2.2 The one design choice to remember: typed AST​

Ora’s AST is not just syntax. Many nodes carry TypeInfo fields that begin unknown and are filled during type resolution.

That means:

  • a lot of “lowering bugs” are actually “typing bugs”
  • if an IR op has the wrong type, check the typed AST first

2.3 Where to stand when you’re confused​

If you feel lost:

  • go back to the artifact ladder (Tokens → AST → Typed AST → MLIR → SIR)
  • run the phase you think is failing in isolation
  • inspect the artifact

That workflow is the real onboarding.