feat: semantic analysis + type checker (Phase 2)

src/scope.nim

@@ -0,0 +1,47 @@
+import types, ast, source_location
+
+type
+  SymbolKind* = enum
+    skVar
+    skFunc
+    skType
+    skConst
+    skModule
+
+  Symbol* = ref object
+    kind*: SymbolKind
+    name*: string
+    typ*: Type
+    decl*: Decl        ## optional back-reference to AST decl
+    isMutable*: bool
+    isPublic*: bool
+
+  Scope* = ref object
+    parent*: Scope
+    symbols*: seq[Symbol]
+
+proc newScope*(parent: Scope = nil): Scope =
+  result = Scope(parent: parent)
+
+proc define*(scope: Scope, sym: Symbol): bool =
+  ## Returns false if name already exists in this scope
+  for s in scope.symbols:
+    if s.name == sym.name:
+      return false
+  scope.symbols.add(sym)
+  return true
+
+proc lookup*(scope: Scope, name: string): Symbol =
+  var cur = scope
+  while cur != nil:
+    for s in cur.symbols:
+      if s.name == name:
+        return s
+    cur = cur.parent
+  return nil
+
+proc lookupLocal*(scope: Scope, name: string): Symbol =
+  for s in scope.symbols:
+    if s.name == name:
+      return s
+  return nil