Module: MilkTea::Linter::LinterVisitors

Included in:
MilkTea::Linter
Defined in:
lib/milk_tea/tooling/linter/visitors.rb

Constant Summary collapse

BINARY_OP_CHARS = 
%w[+ - * / % & | ^ < > = ! ? :]
BORROW_CALL_NAMES =

── borrow facts helpers ──────────────────────────────────────────────────

%w[ref_of ptr_of].freeze

Instance Method Summary collapse

Instance Method Details

#alloc_wrapper_name(expr) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 652

def alloc_wrapper_name(expr)
  return nil unless expr.is_a?(AST::Call)
  return nil unless expr.callee.is_a?(AST::Identifier)

  name = expr.callee.name
  %w[alloc_expr alloc_stmt alloc_decl].include?(name) ? name : nil
end

#boolean_literal_value(expr) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 736

def boolean_literal_value(expr)
  expr.is_a?(AST::BooleanLiteral) ? expr.value : nil
end

#check_prefer_conditional_expression_if(statement) ⇒ Object

prefer-conditional-expression: if/match whose every branch either returns a value or assigns the same lvalue can become an expression form (return if …: … else: … or x = match …).



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 862

def check_prefer_conditional_expression_if(statement)
  return unless statement.else_body

  stmts = (statement.branches.map(&:body) + [statement.else_body]).map { |b| single_statement_body(b) }
  return if inline_if_too_wide?(statement, stmts)
  report_conditional_expression(stmts, line: statement.line, column: statement.branches.first&.column, kind: "if")
end

#check_prefer_conditional_expression_match(statement) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 870

def check_prefer_conditional_expression_match(statement)
  return unless statement.arms.any? { |arm| wildcard_pattern?(arm.pattern) }
  return if statement.arms.any? { |arm| arm.binding_name }

  stmts = statement.arms.map { |arm| single_statement_body(arm.body) }
  report_conditional_expression(stmts, line: statement.line, column: statement.column, kind: "match")
end

#check_prefer_inline_if(statement) ⇒ Object

prefer-inline-if: a block-form if/else whose every branch is a single simple statement can be written on one line.



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 785

def check_prefer_inline_if(statement)
  return if statement.inline
  return unless statement.else_body

  bodies = statement.branches.map(&:body) + [statement.else_body]
  stmts = bodies.map { |b| single_statement_body(b) }
  return if stmts.any?(&:nil?)
  return unless stmts.all? { |s| inline_simple_statement?(s) }

  return if visually_inline_if?(statement, stmts)
  return if inline_if_too_wide?(statement, stmts)

  emit_conciseness_hint(
    "prefer-inline-if",
    line: statement.line,
    column: statement.branches.first&.column,
    message: "if/else with single-statement branches can be written inline",
  )
end

#check_prefer_is_variant(match_expr) ⇒ Object

Detects a two-arm match expression that only maps a single variant arm to a boolean and everything else to the opposite boolean, e.g. match token: TokenKind.eof: true; _: false which is exactly what token is TokenKind.eof desugars to. Only fires when the scrutinee is a variant (the is operator is variant-only), so enum/int/str bool-matches are never misreported.



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 686

def check_prefer_is_variant(match_expr)
  return unless @sema_facts
  return if match_expr.desugared_from_is

  arms = match_expr.arms
  return unless arms.size == 2

  wildcard_arm, arm_pattern_arm = classify_is_variant_arms(arms)
  return unless wildcard_arm && arm_pattern_arm

  # The variant arm must be a bare `Type.arm` reference: no payload
  # destructure and no `as` binding, otherwise it is not equivalent to `is`.
  pattern = arm_pattern_arm.pattern
  return unless pattern.is_a?(AST::MemberAccess)
  return unless arm_pattern_arm.binding_name.nil?

  variant_value = boolean_literal_value(arm_pattern_arm.value)
  wildcard_value = boolean_literal_value(wildcard_arm.value)
  return if variant_value.nil? || wildcard_value.nil?
  return if variant_value == wildcard_value

  scrutinee_type = resolve_expr_type(match_expr.expression)
  return unless scrutinee_type.is_a?(Types::Variant)

  arm_text = expr_source_name(pattern)
  suggestion = variant_value ? "expr is #{arm_text}" : "not (expr is #{arm_text})"

  @warnings << Warning.new(
    path: @path,
    line: match_expr.line,
    column: match_expr.column,
    length: match_expr.length,
    code: "prefer-is-variant",
    message: "prefer `#{suggestion}` over a match that maps one variant arm to a boolean",
    severity: :hint,
  )
end

#check_prefer_or_pattern(arms, body_of:) ⇒ Object

prefer-or-pattern: adjacent match arms with identical bodies and no bindings can be merged with |.



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 902

def check_prefer_or_pattern(arms, body_of:)
  arms.each_cons(2) do |first, second|
    next if first.binding_name || second.binding_name
    next if wildcard_pattern?(first.pattern) || wildcard_pattern?(second.pattern)
    next if body_of.call(first).equal?(body_of.call(second))
    next unless node_fingerprint(body_of.call(first)) == node_fingerprint(body_of.call(second))

    pattern = second.pattern
    pattern_line = pattern.line || second.binding_line
    pattern_column = pattern.column || second.binding_column
    emit_conciseness_hint(
      "prefer-or-pattern",
      line: pattern_line,
      column: pattern_column,
      message: "adjacent match arms have identical bodies; merge them with `|`",
    )
  end
end

#check_prefer_struct_with(call) ⇒ Object

prefer-struct-with: a constructor literal that copies all-but-one field from the same source value can use .with(...).



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 923

def check_prefer_struct_with(call)
  return unless @sema_facts
  return unless call.callee.is_a?(AST::Identifier) || call.callee.is_a?(AST::MemberAccess)
  return if call.arguments.empty?
  return unless call.arguments.all? { |arg| arg.name }

  copied, changed = call.arguments.partition { |arg| copy_field_argument?(arg) }
  return unless changed.size >= 1 && copied.size >= 2

  sources = copied.map { |arg| node_fingerprint(arg.value.receiver) }.uniq
  return unless sources.size == 1

  struct_type = resolve_expr_type(call)
  return unless struct_type.is_a?(Types::Struct)
  source_type = resolve_expr_type(copied.first.value.receiver)
  return unless source_type.equal?(struct_type) || (source_type.respond_to?(:name) && source_type.name == struct_type.name)

  field_names = struct_type.fields.keys.map(&:to_s).to_set
  copied_names = copied.map { |arg| arg.name.to_s }.to_set
  changed_names = changed.map { |arg| arg.name.to_s }
  return unless (field_names - changed_names.to_set) == copied_names

  source_text = expr_source_name(copied.first.value.receiver)
  emit_conciseness_hint(
    "prefer-struct-with",
    line: call.callee.line,
    column: call.callee.column,
    message: "copies #{copied.size} field(s) from `#{source_text}`; use `#{source_text}.with(#{changed_names.join(", ")} = …)`",
  )
end

#check_prefer_try(scrutinee, arms) ⇒ Object

prefer-try: a two-arm match on Result/Option whose failure/none arm only returns is error-propagation and can usually be written expr?.



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 961

def check_prefer_try(scrutinee, arms)
  return unless @sema_facts
  return unless arms.size == 2

  scrutinee_type = resolve_expr_type(scrutinee)
  return unless scrutinee_type.is_a?(Types::Variant)
  base = scrutinee_type.name.to_s.split(".").last
  return unless %w[Result Option].include?(base)

  early_return_arm = arms.find do |arm|
    stmt = single_statement_body(arm.body)
    next false unless stmt.is_a?(AST::ReturnStmt) && stmt.value
    next false unless short_circuit_arm_pattern?(arm.pattern, base)

    propagation_return?(stmt.value, base, arm.binding_name)
  end
  return unless early_return_arm

  emit_conciseness_hint(
    "prefer-try",
    line: scrutinee.line,
    column: scrutinee.column,
    message: "this #{base} match only propagates the failure branch; consider `expr?`",
  )
end

#check_redundant_cast(cast_expr) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 1021

def check_redundant_cast(cast_expr)
  return unless cast_expr.is_a?(AST::PrefixCast)
  return unless cast_expr.target_type

  target_name = type_ref_name(cast_expr.target_type)
  return unless target_name

  # When facts are available compare the *full* resolved types, not just
  # the nominal base name. Comparing names alone wrongly treats e.g.
  # `ptr[void]<-p` (p: ptr[ubyte]) as same-type because both are "ptr",
  # and removing that cast is a real type error.
  if @sema_facts
    cast_type = resolve_expr_type(cast_expr)
    inner_type = resolve_expr_type(cast_expr.expression)
    if cast_type && inner_type
      emit_redundant_cast(cast_expr, target_name, "cast to same type is redundant") if same_resolved_type?(cast_type, inner_type)
      if own_to_pointer_cast_redundant?(inner_type, cast_type)
        emit_redundant_cast(cast_expr, target_name, "implicit own->ptr coercion makes this cast redundant")
      end
      return
    end
  end

  # Fallback when the inner type cannot be resolved (e.g. no sema facts):
  # a value literal whose type is known by name.
  literal_name = expression_literal_type_name(cast_expr.expression)
  if literal_name && literal_name == target_name
    emit_redundant_cast(cast_expr, target_name, "cast to same type is redundant")
  end

  # NOTE: widening redundancy is intentionally NOT reported here. A
  # widening cast can be load-bearing at its site (e.g. `(ulong<-x) << 32`
  # controls the shift width), so it is only redundant at a coercion
  # boundary whose declared type is the target. Those cases are handled by
  # check_boundary_widening_cast at the specific boundary sites.
end

#check_redundant_cast_parens(cast) ⇒ Object

── redundant cast parentheses ──────────────────────────────────────────────────── T<-(x) when T<-x would be equivalent because the inner expression needs no precedence protection. Parens are required when the inner expression contains a binary operator, range, or inline conditional.



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 1063

def check_redundant_cast_parens(cast)

  line_idx = Integer(cast.line) - 1
  return if line_idx < 0 || line_idx >= @source_lines.length

  line = @source_lines[line_idx].to_s
  col = Integer(cast.column) - 1
  arrow = line.index("<-", col)
  return unless arrow
  arrow_end = arrow + 2
  return if arrow_end >= line.length
  return unless line[arrow_end] == "("

  close = match_paren(line, arrow_end)
  return unless close

  inner = line[arrow_end + 1...close].strip
  return if inner.empty?
  return if inner_has_top_level_operators?(inner)

  emit_redundant_cast(cast, type_ref_name(cast.target_type) || "",
    "parentheses around cast expression are redundant")
end

#check_redundant_type_annotation(statement) ⇒ Object

── redundant type annotation ─────────────────────────────────────────────



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 600

def check_redundant_type_annotation(statement)
  return unless statement.is_a?(AST::LocalDecl)
  return unless statement.kind == :let
  return unless statement.type
  return unless statement.value

  return if statement.type.nullable

  declared_name = type_ref_name(statement.type)
  return unless declared_name

  inferred_name = expression_literal_type_name(statement.value)
  return unless inferred_name
  return unless declared_name == inferred_name

  @warnings << Warning.new(
    path: @path,
    line: statement.line,
    column: statement.column,
    length: statement.name.length,
    code: "redundant-type-annotation",
    message: "type annotation ': #{declared_name}' is redundant, inferred from initializer",
    severity: :hint,
    symbol_name: statement.name,
  )
end

#classify_is_variant_arms(arms) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 724

def classify_is_variant_arms(arms)
  wildcard = arms.find { |arm| wildcard_pattern?(arm.pattern) }
  other = arms.find { |arm| !wildcard_pattern?(arm.pattern) }
  return [nil, nil] unless wildcard && other

  [wildcard, other]
end

#collect_borrowed_names(stmts) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 1221

def collect_borrowed_names(stmts)
  names = Set.new
  stmts.each { |s| collect_borrows_from_stmt(s, names) }
  names
end

#collect_borrows_from_expr(expr, names, inside_call_argument: false) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 1262

def collect_borrows_from_expr(expr, names, inside_call_argument: false)
  case expr
  when nil then nil
  when AST::Call
    if !inside_call_argument && expr.callee.is_a?(AST::Identifier) && BORROW_CALL_NAMES.include?(expr.callee.name)
      arg = expr.arguments.first
      if arg&.value.is_a?(AST::Identifier)
        names << arg.value.name
      end
    else
      collect_borrows_from_expr(expr.callee, names)
      expr.arguments.each { |a| collect_borrows_from_expr(a.value, names, inside_call_argument: true) }
    end
  when AST::UnaryOp  then collect_borrows_from_expr(expr.operand, names, inside_call_argument:)
  when AST::BinaryOp
    collect_borrows_from_expr(expr.left, names, inside_call_argument:)
    collect_borrows_from_expr(expr.right, names, inside_call_argument:)
  when AST::IfExpr
    collect_borrows_from_expr(expr.condition, names, inside_call_argument:)
    collect_borrows_from_expr(expr.then_expression, names, inside_call_argument:)
    collect_borrows_from_expr(expr.else_expression, names, inside_call_argument:)
  when AST::AwaitExpr
    collect_borrows_from_expr(expr.expression, names, inside_call_argument:)
  when AST::UnsafeExpr
    collect_borrows_from_expr(expr.expression, names, inside_call_argument:)
  when AST::MemberAccess  then collect_borrows_from_expr(expr.receiver, names, inside_call_argument:)
  when AST::IndexAccess
    collect_borrows_from_expr(expr.receiver, names, inside_call_argument:)
    collect_borrows_from_expr(expr.index, names, inside_call_argument:)
  end
end

#collect_borrows_from_stmt(stmt, names) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 1227

def collect_borrows_from_stmt(stmt, names)
  case stmt
  when AST::LocalDecl
    collect_borrows_from_expr(stmt.value, names) if stmt.value
  when AST::Assignment
    collect_borrows_from_expr(stmt.value, names)
  when AST::ExpressionStmt
    collect_borrows_from_expr(stmt.expression, names)
  when AST::IfStmt
    stmt.branches.each do |b|
      collect_borrows_from_expr(b.condition, names)
      b.body.each { |s| collect_borrows_from_stmt(s, names) }
    end
    stmt.else_body&.each { |s| collect_borrows_from_stmt(s, names) }
  when AST::WhileStmt
    collect_borrows_from_expr(stmt.condition, names)
    stmt.body.each { |s| collect_borrows_from_stmt(s, names) }
  when AST::ForStmt
    stmt.body.each { |s| collect_borrows_from_stmt(s, names) }
  when AST::ReturnStmt
    collect_borrows_from_expr(stmt.value, names) if stmt.value
  when AST::MatchStmt
    collect_borrows_from_expr(stmt.expression, names)
    stmt.arms.each { |arm| arm.body.each { |s| collect_borrows_from_stmt(s, names) } }
  when AST::UnsafeStmt
    stmt.body.each { |s| collect_borrows_from_stmt(s, names) }
  when AST::DeferStmt
    stmt.body.each { |s| collect_borrows_from_stmt(s, names) }
  when AST::WhenStmt
    collect_borrows_from_expr(stmt.discriminant, names)
    stmt.branches.each { |b| b.body.each { |s| collect_borrows_from_stmt(s, names) } }
    stmt.else_body&.each { |s| collect_borrows_from_stmt(s, names) }
  end
end

#collect_writes_from_stmt(stmt, names) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 1300

def collect_writes_from_stmt(stmt, names)
  case stmt
  when AST::Assignment
    names << stmt.target.name if stmt.target.is_a?(AST::Identifier)
    collect_writes_from_stmt_list(stmt_sub_stmts(stmt), names)
  when AST::IfStmt
    stmt.branches.each { |b| b.body.each { |s| collect_writes_from_stmt(s, names) } }
    stmt.else_body&.each { |s| collect_writes_from_stmt(s, names) }
  when AST::WhileStmt
    stmt.body.each { |s| collect_writes_from_stmt(s, names) }
  when AST::ForStmt
    stmt.body.each { |s| collect_writes_from_stmt(s, names) }
  when AST::MatchStmt
    stmt.arms.each { |arm| arm.body.each { |s| collect_writes_from_stmt(s, names) } }
  when AST::WhenStmt
    stmt.branches.each { |b| b.body.each { |s| collect_writes_from_stmt(s, names) } }
    stmt.else_body&.each { |s| collect_writes_from_stmt(s, names) }
  when AST::UnsafeStmt
    stmt.body.each { |s| collect_writes_from_stmt(s, names) }
  when AST::DeferStmt
    stmt.body.each { |s| collect_writes_from_stmt(s, names) }
  end
end

#collect_writes_from_stmt_list(stmts, names) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 1324

def collect_writes_from_stmt_list(stmts, names)
  stmts.each { |s| collect_writes_from_stmt(s, names) }
end

#collect_written_names(stmts) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 1294

def collect_written_names(stmts)
  names = Set.new
  stmts.each { |s| collect_writes_from_stmt(s, names) }
  names
end

#copy_field_argument?(argument) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 954

def copy_field_argument?(argument)
  value = argument.value
  value.is_a?(AST::MemberAccess) && value.member.to_s == argument.name.to_s
end

#declare_local(name, line, column: nil, var: false) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 464

def declare_local(name, line, column: nil, var: false)
  return if ignored_binding_name?(name)

  resolve_reserved_primitive_name_conflicts!(name)

  replacement_name = nil
  replacement_base_name = nil
  if RESERVED_VALUE_TYPE_NAMES.include?(name)
    replacement_base_name = suggested_reserved_primitive_name(name, kind_label: "local")
    replacement_name = next_available_reserved_primitive_name(
      replacement_base_name,
      visible_binding_names(excluding_name: name),
    )
  end

  # shadow: check whether any outer scope already has a binding for this name
  if @scopes.length > 1
    @scopes[0..-2].each do |outer_scope|
      if outer_scope.key?(name)
        @warnings << Warning.new(
          path: @path, line:, column:, length: name.length, code: "shadow",
          message: "local '#{name}' shadows a binding from an outer scope",
          symbol_name: name
        )
        break
      end
    end
  end

  @scopes.last[name] = Binding.new(
    name:, line:, column:, used: false,
    binding_kind: :local,
    allow_prefer_let: var && !generic_function_context?,
    mutated: false,
    replacement_name:,
    replacement_base_name:,
  )
  register_reserved_primitive_name_fix(@scopes.last[name], kind_label: "local", replacement_name:) if replacement_name
end

#declare_param(name, line: nil, column: nil) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 503

def declare_param(name, line: nil, column: nil)
  return if ignored_binding_name?(name)

  resolve_reserved_primitive_name_conflicts!(name)

  replacement_name = nil
  replacement_base_name = nil
  if RESERVED_VALUE_TYPE_NAMES.include?(name)
    replacement_base_name = suggested_reserved_primitive_name(name, kind_label: "parameter")
    replacement_name = next_available_reserved_primitive_name(
      replacement_base_name,
      visible_binding_names(excluding_name: name),
    )
  end

  @scopes.last[name] = Binding.new(
    name:, line:, column:, used: false,
    binding_kind: :param,
    allow_prefer_let: false,
    mutated: false,
    replacement_name:,
    replacement_base_name:,
  )
  register_reserved_primitive_name_fix(@scopes.last[name], kind_label: "parameter", replacement_name:) if replacement_name
end

#declared_callable_names(source_file) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 75

def declared_callable_names(source_file)
  source_file.declarations.each_with_object(Set.new) do |declaration, names|
    case declaration
    when AST::FunctionDef, AST::ExternFunctionDecl, AST::ForeignFunctionDecl,
         AST::ConstDecl, AST::VarDecl, AST::EventDecl
      names << declaration.name
    end
  end
end

#declared_directional_functions(source_file) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 84

def declared_directional_functions(source_file)
  source_file.declarations.each_with_object({}) do |declaration, functions|
    next unless declaration.is_a?(AST::ExternFunctionDecl) || declaration.is_a?(AST::ForeignFunctionDecl)
    next unless declaration.params.any? { |param| %i[in out inout].include?(param.mode) }

    functions[declaration.name] = declaration
  end
end

#editable_receiver_expression?(expression) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 453

def editable_receiver_expression?(expression)
  return true unless @sema_facts

  @sema_facts&.binding_resolution&.editable_receiver_expression_ids&.key?(expression.object_id)
end

#emit_conciseness_hint(code, line:, column:, message:, length: nil) ⇒ Object

── conciseness hints ─────────────────────────────────────────────────



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 750

def emit_conciseness_hint(code, line:, column:, message:, length: nil)
  @warnings << Warning.new(path: @path, line:, column:, length:, code:, message:, severity: :hint)
end

#emit_redundant_cast(cast_expr, target_name, reason) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 1159

def emit_redundant_cast(cast_expr, target_name, reason)
  line = cast_expr.line || expression_line(cast_expr)
  column = cast_expr.column || expression_column(cast_expr)

  @warnings << Warning.new(
    path: @path,
    line: line,
    column: column,
    length: expression_length(cast_expr),
    code: "redundant-cast",
    message: "#{reason}: #{target_name}<-",
    severity: :hint,
  )
end

#emit_scope_warnings(scope) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 554

def emit_scope_warnings(scope)
  scope.each_value do |binding|
    if !binding.used
      code = binding.binding_kind == :param ? "unused-param" : "unused-local"
      kind_label = binding.binding_kind == :param ? "parameter" : "local"
      @warnings << Warning.new(
        path: @path,
        line: binding.line,
        column: binding.column,
        length: binding.name.length,
        code: code,
        message: "unused #{kind_label} '#{binding.name}'",
        symbol_name: binding.name,
      )
    else
      if binding.allow_prefer_let && !binding.mutated
        @warnings << Warning.new(
          path: @path,
          line: binding.line,
          column: binding.column,
          length: binding.name.length,
          code: "prefer-let",
          message: "variable '#{binding.name}' is never reassigned, prefer 'let'",
          severity: :hint,
          symbol_name: binding.name
        )
      end

      uses = @binding_ptr_unsafe_uses[binding.name]
      if binding.binding_kind != :param && uses[:unsafe] > 0 && uses[:safe] == 0 && @ptr_candidates.include?(binding.name)
        @warnings << Warning.new(
          path: @path,
          line: binding.line,
          column: binding.column,
          length: binding.name.length,
          code: "prefer-own-ptr",
          message: "binding '#{binding.name}' is only used inside unsafe — consider converting its type from ptr to own for auto-deref",
          severity: :hint,
          symbol_name: binding.name,
        )
      end
    end
  end
end

#expr_source_name(expr) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 740

def expr_source_name(expr)
  case expr
  when AST::Identifier then expr.name
  when AST::MemberAccess then "#{expr_source_name(expr.receiver)}.#{expr.member}"
  else "…"
  end
end

#expression_literal_type_name(expr) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 1208

def expression_literal_type_name(expr)
  case expr
  when AST::IntegerLiteral then "int"
  when AST::StringLiteral  then expr.cstring ? "cstr" : "str"
  when AST::FloatLiteral   then "float"
  when AST::BooleanLiteral then "bool"
  else nil
  end
end

#extending_block_generic?(declaration) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 72

def extending_block_generic?(declaration)
  declaration.type_name.respond_to?(:arguments) && declaration.type_name.arguments.any?
end

#find_borrow_location(stmts, name) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 1332

def find_borrow_location(stmts, name)
  stmts.each do |stmt|
    location = find_borrow_location_in_stmt(stmt, name)
    return location if location
  end
  nil
end

#find_borrow_location_in_expr(expr, name) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 1390

def find_borrow_location_in_expr(expr, name)
  case expr
  when nil then nil
  when AST::Call
    if expr.callee.is_a?(AST::Identifier) && BORROW_CALL_NAMES.include?(expr.callee.name)
      arg = expr.arguments.first
      if arg&.value.is_a?(AST::Identifier) && arg.value.name == name
        return [arg.value.line, arg.value.column, arg.value.name.length]
      end
    end
    location = find_borrow_location_in_expr(expr.callee, name)
    return location if location
    expr.arguments.each do |a|
      location = find_borrow_location_in_expr(a.value, name)
      return location if location
    end
    nil
  when AST::UnaryOp  then find_borrow_location_in_expr(expr.operand, name)
  when AST::BinaryOp
    find_borrow_location_in_expr(expr.left, name) || find_borrow_location_in_expr(expr.right, name)
  when AST::IfExpr
    find_borrow_location_in_expr(expr.condition, name) ||
      find_borrow_location_in_expr(expr.then_expression, name) ||
      find_borrow_location_in_expr(expr.else_expression, name)
  when AST::AwaitExpr
    find_borrow_location_in_expr(expr.expression, name)
  when AST::UnsafeExpr
    find_borrow_location_in_expr(expr.expression, name)
  else
    nil
  end
end

#find_borrow_location_in_stmt(stmt, name) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 1340

def find_borrow_location_in_stmt(stmt, name)
  case stmt
  when AST::LocalDecl
    find_borrow_location_in_expr(stmt.value, name) if stmt.value
  when AST::Assignment
    find_borrow_location_in_expr(stmt.value, name)
  when AST::ExpressionStmt
    find_borrow_location_in_expr(stmt.expression, name)
  when AST::IfStmt
    stmt.branches.each do |b|
      location = find_borrow_location_in_expr(b.condition, name)
      return location if location
      b.body.each { |s| location = find_borrow_location_in_stmt(s, name); return location if location }
    end
    stmt.else_body&.each { |s| location = find_borrow_location_in_stmt(s, name); return location if location }
    nil
  when AST::WhileStmt
    location = find_borrow_location_in_expr(stmt.condition, name)
    return location if location
    stmt.body.each { |s| location = find_borrow_location_in_stmt(s, name); return location if location }
    nil
  when AST::ForStmt
    stmt.body.each { |s| location = find_borrow_location_in_stmt(s, name); return location if location }
    nil
  when AST::ReturnStmt
    find_borrow_location_in_expr(stmt.value, name) if stmt.value
  when AST::MatchStmt
    location = find_borrow_location_in_expr(stmt.expression, name)
    return location if location
    stmt.arms.each do |arm|
      arm.body.each { |s| location = find_borrow_location_in_stmt(s, name); return location if location }
    end
    nil
  when AST::UnsafeStmt
    stmt.body.each { |s| location = find_borrow_location_in_stmt(s, name); return location if location }
    nil
  when AST::DeferStmt
    stmt.body.each { |s| location = find_borrow_location_in_stmt(s, name); return location if location }
    nil
  when AST::WhenStmt
    location = find_borrow_location_in_expr(stmt.discriminant, name)
    return location if location
    stmt.branches.each do |b|
      b.body.each { |s| location = find_borrow_location_in_stmt(s, name); return location if location }
    end
    stmt.else_body&.each { |s| location = find_borrow_location_in_stmt(s, name); return location if location }
    nil
  end
end

#find_primitive_type(name) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 1191

def find_primitive_type(name)
  return nil unless @sema_facts
  return nil unless @sema_facts.types

  @sema_facts.types[name]
end

#flag_redundant_widening_cast(value) ⇒ Object

Reports a widening cast as redundant only when it sits directly at a coercion slot: the RHS of a typed let/var, a return value, or the RHS of a plain = assignment. At those positions the slot type is pinned by an annotation / return type / declared lvalue, so the value is coerced to that type and never consumed by a width-sensitive operator at the site. Because widening composes losslessly, removing the cast preserves both type and behavior regardless of the exact slot type.

Call arguments and aggregate field initializers are intentionally NOT treated as slots: a generic parameter/field would let the removed cast change type inference (and hence behavior), which is not sound without resolving the callee/struct signature.



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 1129

def flag_redundant_widening_cast(value)
  return unless value.is_a?(AST::PrefixCast)
  return unless @sema_facts

  target_name = type_ref_name(value.target_type)
  return unless target_name

  inner_type = resolve_expr_type(value.expression)
  return unless inner_type.is_a?(Types::Primitive)
  return if inner_type.name == target_name # same-type handled elsewhere
  return unless implicit_cast_allowed?(inner_type, target_name)

  emit_redundant_cast(value, target_name, "implicit widening makes this cast redundant")
end

#generic_function_context? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 128

def generic_function_context?
  @generic_function_depth > 0
end

#heap_alloc_call?(expr) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 645

def heap_alloc_call?(expr)
  return false unless expr.is_a?(AST::Call)
  return false unless expr.callee.is_a?(AST::MemberAccess)

  %w[must_alloc alloc must_alloc_zeroed must_resize].include?(expr.callee.member)
end

#implicit_cast_allowed?(inner_type, target_name) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 1174

def implicit_cast_allowed?(inner_type, target_name)
  return true if inner_type.name == target_name

  target = find_primitive_type(target_name)
  return false unless target
  return false unless target.is_a?(Types::Primitive)
  return false unless inner_type.fixed_width_integer? && target.fixed_width_integer?

  if inner_type.signed_integer? == target.signed_integer?
    return target.integer_width >= inner_type.integer_width
  end

  return false if inner_type.signed_integer?

  target.signed_integer? && target.integer_width > inner_type.integer_width
end

#inline_if_too_wide?(statement, stmts) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 805

def inline_if_too_wide?(statement, stmts)
  return false if statement.branches.empty?

  text = +""

  statement.branches.each_with_index do |b, i|
    cond_src = source_line_from(b.line, b.column)
    return false unless cond_src

    stmt_col = stmts[i]&.column
    stmt_line = stmts[i]&.line
    body_src = source_line_from(stmt_line, stmt_col)
    return false unless body_src

    text << cond_src
    text << " "
    text << body_src
    text << " "
  end

  if statement.else_line
    else_src = source_line_from(statement.else_line, statement.else_column)
    return false unless else_src
    text << else_src
    text << " "
  end

  stmt_col = stmts.last&.column
  stmt_line = stmts.last&.line
  else_body = source_line_from(stmt_line, stmt_col)
  return false unless else_body
  text << else_body

  text.strip.length > 120
end

#inline_simple_statement?(stmt) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 774

def inline_simple_statement?(stmt)
  case stmt
  when AST::ReturnStmt, AST::Assignment, AST::ExpressionStmt, AST::BreakStmt, AST::ContinueStmt, AST::LocalDecl
    true
  else
    false
  end
end

#inner_has_top_level_operators?(inner) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 1100

def inner_has_top_level_operators?(inner)
  depth = 0
  i = 0
  while i < inner.length
    case inner[i]
    when "(", "[", "{"
      depth += 1
    when ")", "]", "}"
      depth -= 1 if depth > 0
    when *BINARY_OP_CHARS
      return true if depth == 0
    end
    i += 1
  end
  false
end

#mark_alias_source_mutated(expression) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 445

def mark_alias_source_mutated(expression)
  return unless expression.is_a?(AST::Call)
  return unless expression.callee.is_a?(AST::Identifier)
  return unless %w[ref_of ptr_of].include?(expression.callee.name)
  return unless expression.arguments.length == 1

  mark_mutated(expression.arguments.first.value)
end

#mark_assignment_target_reads(target, operator) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 380

def mark_assignment_target_reads(target, operator)
  return if operator == "="

  mark_used(target.name, identifier: target) if target.is_a?(AST::Identifier)
end

#mark_call_argument_mutated(expression) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 409

def mark_call_argument_mutated(expression)
  if expression.is_a?(AST::Identifier) && mutating_argument_identifier?(expression)
    mark_mutated(expression)
    return
  end

  if expression.is_a?(AST::UnaryOp) && %w[out inout].include?(expression.operator)
    mark_mutated(expression.operand)
    return
  end

  # ref_of(x) and ptr_of(x) can expose writable aliases — treat as potential
  # mutation since callees may write through them (common C-FFI out-param pattern).
  if expression.is_a?(AST::Call) &&
     expression.callee.is_a?(AST::Identifier) &&
    ["ref_of", "ptr_of"].include?(expression.callee.name) &&
     expression.arguments.length == 1
    mark_mutated(expression.arguments.first.value)
  end
end

#mark_call_receiver_mutated(expression) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 438

def mark_call_receiver_mutated(expression)
  return unless expression.is_a?(AST::Call)
  return unless expression.callee.is_a?(AST::MemberAccess)
  return unless editable_receiver_expression?(expression.callee.receiver)

  mark_mutated(expression.callee.receiver)
end

#mark_mutated(target) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 385

def mark_mutated(target)
  return unless target.is_a?(AST::Identifier) || target.is_a?(AST::IndexAccess) || target.is_a?(AST::MemberAccess)

  # For direct identifier assignment (e.g., x = value), mark x as mutated.
  if target.is_a?(AST::Identifier)
    @scopes.reverse_each do |scope|
      binding = scope[target.name]
      next unless binding

      binding.mutated = true
      return
    end
  end

  # For index assignment (e.g., array[0] = value), mark the array as mutated.
  if target.is_a?(AST::IndexAccess)
    mark_mutated(target.receiver)
  end

  # For field assignment (e.g., rect.w = value), mark the struct variable as mutated.
  if target.is_a?(AST::MemberAccess)
    mark_mutated(target.receiver)
  end
end

#mark_used(name, identifier: nil) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 528

def mark_used(name, identifier: nil)
  @scopes.reverse_each do |scope|
    binding = scope[name]
    next unless binding

    binding.used = true
    track_binding_unsafe_use(name)
    record_reserved_primitive_identifier_use(binding, identifier)
    return
  end

  binding = @module_bindings[name]
  return unless binding

  binding.used = true
  record_reserved_primitive_identifier_use(binding, identifier)
end

#match_paren(line, open_pos) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 1087

def match_paren(line, open_pos)
  depth = 0
  (open_pos...line.length).each do |i|
    case line[i]
    when "(" then depth += 1
    when ")" then depth -= 1; return i if depth == 0
    end
  end
  nil
end

#member_named?(node, name) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 1017

def member_named?(node, name)
  node.is_a?(AST::MemberAccess) && node.member.to_s == name
end

#mutating_argument_identifier?(expression) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 429

def mutating_argument_identifier?(expression)
  return false unless expression.is_a?(AST::Identifier)

  binding_resolution = @sema_facts&.binding_resolution
  return false unless binding_resolution

  binding_resolution.mutating_argument_identifier_ids&.key?(expression.object_id) ||
    binding_resolution.mutable_lvalue_argument_identifier_ids&.key?(expression.object_id)
end

#node_fingerprint(node) ⇒ Object

Position-insensitive structural fingerprint of an AST node, used to test whether two branch/arm bodies are equivalent regardless of source location.



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 757

def node_fingerprint(node)
  case node
  when ::Data
    skip = %i[line column length else_line else_column binding_line binding_column]
    parts = node.deconstruct_keys(nil).reject { |k, _| skip.include?(k) }
    "#{node.class.name}(#{parts.map { |k, v| "#{k}:#{node_fingerprint(v)}" }.join(",")})"
  when Array
    "[#{node.map { |e| node_fingerprint(e) }.join(",")}]"
  else
    node.inspect
  end
end

#own_to_pointer_cast_redundant?(inner_type, cast_type) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 1150

def own_to_pointer_cast_redundant?(inner_type, cast_type)
  return false unless inner_type.is_a?(Types::GenericInstance) && inner_type.name == "own"
  return false unless cast_type.is_a?(Types::GenericInstance)
  return false unless %w[ptr const_ptr].include?(cast_type.name)
  return false unless inner_type.arguments.length == 1 && cast_type.arguments.length == 1

  inner_type.arguments.first.to_s == cast_type.arguments.first.to_s
end

#propagation_return?(value, base, binding_name) ⇒ Boolean

The early-return value must re-propagate the short-circuit case unchanged: Option[_].none, or Result[_, _].failure(error = <b>.error) where <b> is the arm's own binding. This excludes map/map_error patterns (transformed error or value), which expr? cannot express.

Returns:

  • (Boolean) 


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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 998

def propagation_return?(value, base, binding_name)
  if base == "Option"
    return member_named?(value, "none") || (value.is_a?(AST::Call) && member_named?(value.callee, "none"))
  end

  return false unless binding_name
  return false unless value.is_a?(AST::Call) && member_named?(value.callee, "failure")
  return false unless value.arguments.size == 1

  error_arg = value.arguments.first
  return false unless error_arg.name.to_s == "error"

  forwarded = error_arg.value
  forwarded.is_a?(AST::MemberAccess) &&
    forwarded.member.to_s == "error" &&
    forwarded.receiver.is_a?(AST::Identifier) &&
    forwarded.receiver.name == binding_name
end

#record_ptr_candidate(statement) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 627

def record_ptr_candidate(statement)
  return unless statement.is_a?(AST::LocalDecl)
  return unless statement.value

  if statement.type && statement.type.is_a?(AST::TypeRef)
    type_text = type_ref_source(statement.type)
    return unless type_text&.include?("ptr[")
  else
    value = statement.value
    unless heap_alloc_call?(value)
      alloc_name = alloc_wrapper_name(value)
      return unless alloc_name
    end
  end

  @ptr_candidates.add(statement.name)
end

#report_conditional_expression(stmts, line:, column:, kind:) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 878

def report_conditional_expression(stmts, line:, column:, kind:)
  return if stmts.empty? || stmts.any?(&:nil?)
  return if @loop_depth && @loop_depth > 0

  if stmts.all? { |s| s.is_a?(AST::ReturnStmt) && s.value }
    emit_conciseness_hint(
      "prefer-conditional-expression",
      line:, column:,
      message: "every #{kind} branch returns a value; rewrite as `return #{kind} …` expression",
    )
  elsif stmts.all? { |s| s.is_a?(AST::Assignment) && s.operator == "=" } &&
        stmts.all? { |s| s.target.respond_to?(:name) } &&
        stmts.map { |s| node_fingerprint(s.target) }.uniq.size == 1
    target_name = stmts.first.target.name
    emit_conciseness_hint(
      "prefer-conditional-expression",
      line:, column:,
      message: "every #{kind} branch assigns to '#{target_name}'; rewrite as `let #{target_name} = #{kind} …` expression",
    )
  end
end

#resolve_expr_type(expr) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 1198

def resolve_expr_type(expr)
  return nil unless @sema_facts
  return nil unless expr

  node_id = @sema_facts.ast.node_ids[expr.object_id]
  return nil unless node_id

  @sema_facts.resolved_expr_types[node_id]
end

#same_resolved_type?(left, right) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 1144

def same_resolved_type?(left, right)
  return true if left.equal?(right)

  left.to_s == right.to_s
end

#seed_module_bindings(source_file) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 28

def seed_module_bindings(source_file)
  @module_bindings = {}

  import_names = source_file.imports.filter_map do |import|
    import.alias_name || import.path.parts.last
  end
  source_file.imports.each do |import|
    local_name = import.alias_name || import.path.parts.last
    next if ignored_binding_name?(local_name)

    declare_reserved_import_alias_module_binding(
      local_name,
      kind_label: "import alias",
      line: import.line,
      column: import.column,
      unavailable_names: import_names,
    )
  end

  source_file.declarations.each do |declaration|
    kind_label = case declaration
                 when AST::FunctionDef, AST::ExternFunctionDecl, AST::ForeignFunctionDecl
                   "function"
                 when AST::ConstDecl
                   "constant"
                 when AST::VarDecl
                   "module variable"
                 when AST::EventDecl
                   "event"
                 else
                   nil
                 end
    next unless kind_label
    next if ignored_binding_name?(declaration.name)

    declare_reserved_primitive_module_binding(
      declaration.name,
      kind_label:,
      line: declaration.line,
      column: declaration_column(declaration),
      unavailable_names: @declared_callable_names,
    )
  end
end

#short_circuit_arm_pattern?(pattern, base) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 987

def short_circuit_arm_pattern?(pattern, base)
  name = pattern.is_a?(AST::MemberAccess) ? pattern.member.to_s : nil
  return false unless name

  (base == "Result" && name == "failure") || (base == "Option" && name == "none")
end

#single_statement_body(body) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 770

def single_statement_body(body)
  body.is_a?(Array) && body.size == 1 ? body.first : nil
end

#source_line_from(line, column) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 841

def source_line_from(line, column)
  return nil unless line
  line_idx = Integer(line) - 1
  return nil if line_idx < 0 || line_idx >= @source_lines.length
  raw = @source_lines[line_idx].to_s
  return raw.strip if column.nil?
  raw[Integer(column) - 1..]&.strip
end

#stmt_sub_stmts(_stmt) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 1328

def stmt_sub_stmts(_stmt)
  []
end

#terminator?(stmt) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 140

def terminator?(stmt)
  stmt.is_a?(AST::ReturnStmt) || stmt.is_a?(AST::BreakStmt) || stmt.is_a?(AST::ContinueStmt)
end

#track_binding_unsafe_use(name) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 546

def track_binding_unsafe_use(name)
  uses = @binding_ptr_unsafe_uses[name]
  if @unsafe_depth > 0
    uses[:unsafe] += 1
  else
    uses[:safe] += 1
  end
end

#type_ref_name(type_node) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 669

def type_ref_name(type_node)
  return nil unless type_node.is_a?(AST::TypeRef)
  return nil if type_node.name.parts.empty?

  type_node.name.parts.first
rescue StandardError
  nil
end

#type_ref_source(type_node) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 660

def type_ref_source(type_node)
  return nil unless type_node.is_a?(AST::TypeRef)
  return nil if type_node.name.parts.empty?

  type_node.name.parts.last
rescue StandardError
  nil
end

#visit_assignment_target(target) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 367

def visit_assignment_target(target)
  case target
  when AST::Identifier
    nil
  when AST::MemberAccess
    visit_expression(target.receiver)
  when AST::IndexAccess
    visit_expression(target.receiver)
    visit_expression(target.index)
  else
    visit_expression(target)
  end
end

#visit_expression(expression) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 250

def visit_expression(expression)
  case expression
  when nil
    nil
  when AST::Identifier
    mark_used(expression.name, identifier: expression)
  when AST::MemberAccess
    visit_expression(expression.receiver)
  when AST::IndexAccess
    visit_expression(expression.receiver)
    visit_expression(expression.index)
  when AST::Specialization
    visit_expression(expression.callee)
    expression.arguments.each { |argument| visit_type_argument(argument) }
  when AST::Call
    visit_expression(expression.callee)
    expression.arguments.each do |argument|
      visit_expression(argument.value)
      mark_call_argument_mutated(argument.value)
    end
    mark_alias_source_mutated(expression)
    mark_call_receiver_mutated(expression)
    check_directional_ffi_call(expression)
    check_prefer_struct_with(expression) if full_tier?
  when AST::UnaryOp
    visit_expression(expression.operand)
  when AST::BinaryOp
    visit_expression(expression.left)
    visit_expression(expression.right)
    check_self_comparison(expression)
    check_redundant_bool_compare(expression)
  when AST::RangeExpr
    visit_expression(expression.start_expr)
    visit_expression(expression.end_expr)
  when AST::ExpressionList
    expression.elements.each { |e| visit_expression(e) }
  when AST::IfExpr
    visit_expression(expression.condition)
    visit_expression(expression.then_expression)
    visit_expression(expression.else_expression)
  when AST::MatchExpr
    visit_expression(expression.expression)
    expression.arms.each do |arm|
      with_scope do
        binding_line = arm.binding_line || expression.line
        binding_column = arm.binding_column
        warn_redundant_ignored_match_binding(arm.binding_name, line: binding_line, column: binding_column)
        declare_local(arm.binding_name, binding_line, column: binding_column, var: false) if arm.binding_name
        visit_expression(arm.value)
      end
    end
    if full_tier?
      check_prefer_is_variant(expression)
      check_prefer_or_pattern(expression.arms, body_of: ->(arm) { arm.value })
    end
  when AST::UnsafeExpr
    @unsafe_depth += 1
    visit_expression(expression.expression)
    @unsafe_depth -= 1
  when AST::ProcExpr
    with_scope do
      fallback_line = expression.line
      expression.params.each do |param|
        declare_param(
          param.name,
          line: param_line(param, fallback: fallback_line),
          column: param_column(param)
        )
      end
      visit_statement_list(expression.body)
      if full_tier?
        emit_dead_assignment_warnings(expression.body)
        emit_unreachable_warnings(expression.body)
        emit_borrow_warnings(expression.body)
        emit_constant_condition_warnings(expression.body)
        emit_redundant_null_check_warnings(expression.body)
        emit_loop_single_iteration_warnings(expression.body)
        emit_owning_release_warnings(expression.body)
      end
      emit_prefer_let_else_warnings(expression.body)
      emit_prefer_var_else_warnings(expression.body)
    end
  when AST::AwaitExpr
    visit_expression(expression.expression)
  when AST::FormatString
    expression.parts.each do |part|
      next unless part.is_a?(AST::FormatExprPart)

      visit_expression(part.expression)
    end
  when AST::IntegerLiteral, AST::FloatLiteral, AST::StringLiteral, AST::BooleanLiteral, AST::NullLiteral
    nil
  when AST::SizeofExpr, AST::AlignofExpr
    visit_type_ref(expression.type)
  when AST::OffsetofExpr
    mark_used(expression.field)
  when AST::PrefixCast
    visit_expression(expression.expression)
    check_redundant_cast(expression)
    check_redundant_cast_parens(expression)
  else
    nil
  end
end

#visit_function(function, generic_context: false) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 92

def visit_function(function, generic_context: false)
  generic_body = generic_context || function.type_params.any?
  @generic_function_depth += 1 if generic_body
  @current_function_stack << function
  with_scope do
    profile_phase("rule.reserved_primitive_type_params") do
      warn_reserved_primitive_type_params(function.type_params, kind_label: "type parameter")
    end
    profile_phase("declare_params") do
      function.params.each do |param|
        declare_param(
          param.name,
          line: param_line(param, fallback: function.line),
          column: param_column(param)
        )
      end
    end
    profile_phase("visit_statement_list") { visit_statement_list(function.body) }
    if full_tier?
      profile_phase("rule.dead_assignment") { emit_dead_assignment_warnings(function.body) }
      profile_phase("rule.unreachable") { emit_unreachable_warnings(function.body) }
      profile_phase("rule.borrow") { emit_borrow_warnings(function.body) }
      profile_phase("rule.constant_condition") { emit_constant_condition_warnings(function.body) }
      profile_phase("rule.redundant_null_check") { emit_redundant_null_check_warnings(function.body) }
      profile_phase("rule.loop_single_iteration") { emit_loop_single_iteration_warnings(function.body) }
    end
    profile_phase("rule.owning_release") { emit_owning_release_warnings(function) }
    profile_phase("rule.prefer_let_else") { emit_prefer_let_else_warnings(function.body) }
    profile_phase("rule.prefer_var_else") { emit_prefer_var_else_warnings(function.body) }
    profile_phase("rule.redundant_return") { emit_redundant_return_warnings(function) }
  end
  profile_phase("rule.missing_return") { check_missing_return(function) }
ensure
  @current_function_stack.pop
  @generic_function_depth -= 1 if generic_body
end

#visit_source_file(source_file) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 6

def visit_source_file(source_file)
  @declared_callable_names = declared_callable_names(source_file)
  @declared_directional_functions = declared_directional_functions(source_file)
  profile_phase("seed_module_bindings") { seed_module_bindings(source_file) }
  profile_phase("rule.unused_imports") { check_unused_imports(source_file) }
  profile_phase("rule.platform_api_drift") { check_platform_api_drift(source_file) } if full_tier?
  source_file.declarations.each do |declaration|
    case declaration
    when AST::FunctionDef
      visit_function(declaration)
    when AST::MethodDef
      warn_reserved_primitive_name(declaration.name, line: declaration.line, column: declaration.column, kind_label: "function")
      visit_function(declaration)
    when AST::ExtendingBlock
      generic_context = extending_block_generic?(declaration)
      declaration.methods.each do |method|
        warn_reserved_primitive_name(method.name, line: method.line, column: method.column, kind_label: "function")
        visit_function(method, generic_context:)
      end
    end
  end
end

#visit_statement(statement) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 143

def visit_statement(statement)
  case statement
  when AST::LocalDecl
    visit_expression(statement.value) if statement.value
    declare_local(
      statement.name,
      statement.line,
      column: statement.column,
      var: statement.kind == :var
    )
    if statement.else_body || statement.else_binding
      with_scope do
        if statement.else_binding
          declare_local(
            statement.else_binding.name,
            statement.else_binding.line,
            column: statement.else_binding.column,
            var: false
          )
        end
        visit_statement_list(statement.else_body) if statement.else_body
      end
    end
    check_redundant_type_annotation(statement)
    flag_redundant_widening_cast(statement.value) if statement.type && statement.value
    record_ptr_candidate(statement)
  when AST::Assignment
    visit_expression(statement.value)          # visit RHS first — reads in RHS count against dead-assignment
    mark_assignment_target_reads(statement.target, statement.operator) # compound: marks target as read
    visit_assignment_target(statement.target)  # non-identifier sub-expressions in target
    mark_mutated(statement.target)
    check_self_assignment(statement)
    check_noop_compound_assignment(statement)
    flag_redundant_widening_cast(statement.value) if statement.operator == "="
  when AST::IfStmt
    statement.branches.each do |branch|
      visit_expression(branch.condition)
      with_scope { visit_statement_list(branch.body) }
    end
    with_scope { visit_statement_list(statement.else_body) } if statement.else_body
    check_redundant_else(statement)
    check_duplicate_if_conditions(statement)
    if full_tier?
      check_prefer_inline_if(statement)
      check_prefer_conditional_expression_if(statement)
    end
  when AST::MatchStmt
    visit_expression(statement.expression)
    statement.arms.each do |arm|
      with_scope do
        binding_line = arm.binding_line || statement.line
        binding_column = arm.binding_column
        warn_redundant_ignored_match_binding(arm.binding_name, line: binding_line, column: binding_column)
        declare_local(arm.binding_name, binding_line, column: binding_column, var: false) if arm.binding_name
        visit_statement_list(arm.body)
      end
    end
    if full_tier?
      check_prefer_conditional_expression_match(statement)
      check_prefer_or_pattern(statement.arms, body_of: ->(arm) { arm.body })
      check_prefer_try(statement.expression, statement.arms)
    end
  when AST::UnsafeStmt
    @unsafe_depth += 1
    with_scope { visit_statement_list(statement.body) }
    @unsafe_depth -= 1
  when AST::ForStmt
    @loop_depth ||= 0
    @loop_depth += 1
    visit_expression(statement.iterable)
    with_scope do
      declare_local(statement.name, statement.line, column: statement.column, var: false) if statement.name
      visit_statement_list(statement.body)
    end
    @loop_depth -= 1
  when AST::WhileStmt
    @loop_depth ||= 0
    @loop_depth += 1
    visit_expression(statement.condition)
    with_scope { visit_statement_list(statement.body) }
    @loop_depth -= 1
  when AST::ReturnStmt
    visit_expression(statement.value) if statement.value
    flag_redundant_widening_cast(statement.value) if statement.value
  when AST::DeferStmt
    with_scope { visit_statement_list(statement.body) }
  when AST::ExpressionStmt
    visit_expression(statement.expression)
    check_useless_expression(statement)
  when AST::GatherStmt
    statement.handles.each { |handle| mark_used(handle.name) if handle.is_a?(AST::Identifier) }
  when AST::StaticAssert
    visit_expression(statement.condition)
  when AST::BreakStmt, AST::ContinueStmt
    nil
  when AST::WhenStmt
    visit_expression(statement.discriminant)
    statement.branches.each do |branch|
      with_scope { visit_statement_list(branch.body) }
    end
    with_scope { visit_statement_list(statement.else_body) } if statement.else_body
  when AST::ErrorBlockStmt
    with_scope { visit_statement_list(statement.body) } if statement.body
  else
    nil
  end
end

#visit_statement_list(stmts) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 131

def visit_statement_list(stmts)
  terminated = false
  stmts.each do |stmt|
    next if terminated  # skip visitation only; ControlFlow emits the warning

    visit_statement(stmt)
    terminated = true if terminator?(stmt)
  end
end

#visit_type_argument(argument) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 354

def visit_type_argument(argument)
  visit_expression(argument.value) if argument.respond_to?(:value)
end

#visit_type_ref(type_ref) ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 357

def visit_type_ref(type_ref)
  return unless type_ref

  type_ref.name.parts.each { |part| mark_used(part) }
  type_ref.arguments.each do |argument|
    next unless argument.respond_to?(:value)

    visit_type_ref(argument.value) if argument.value.is_a?(AST::TypeRef)
  end
end

#visually_inline_if?(statement, stmts) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 850

def visually_inline_if?(statement, stmts)
  n = statement.branches.length
  statement.branches.each_with_index.all? { |b, i|
    stmts[i].line == b.line
  } && (
    stmts[n].line && statement.else_line && stmts[n].line == statement.else_line
  )
end

#wildcard_pattern?(pattern) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 732

def wildcard_pattern?(pattern)
  pattern.is_a?(AST::Identifier) && pattern.name == "_"
end

#with_scope ⇒ Object 



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# File 'lib/milk_tea/tooling/linter/visitors.rb', line 458

def with_scope
  @scopes << {}
  yield
ensure
  emit_scope_warnings(@scopes.pop)
end