diff --git a/Library/Homebrew/build_environment.rb b/Library/Homebrew/build_environment.rb
index 2392b98d5c..d63604faa9 100644
--- a/Library/Homebrew/build_environment.rb
+++ b/Library/Homebrew/build_environment.rb
@@ -55,22 +55,23 @@ class BuildEnvironment
   ].freeze
   private_constant :KEYS
 
-  sig { params(env: T.untyped).returns(T::Array[String]) }
+  sig { params(env: T::Hash[String, T.nilable(T.any(String, Pathname))]).returns(T::Array[String]) }
   def self.keys(env)
     KEYS & env.keys
   end
 
-  sig { params(env: T.untyped, f: IO).void }
+  sig { params(env: T::Hash[String, T.nilable(T.any(String, Pathname))], f: IO).void }
   def self.dump(env, f = $stdout)
     keys = self.keys(env)
     keys -= %w[CC CXX OBJC OBJCXX] if env["CC"] == env["HOMEBREW_CC"]
 
     keys.each do |key|
       value = env.fetch(key)
+
       s = +"#{key}: #{value}"
       case key
       when "CC", "CXX", "LD"
-        s << " => #{Pathname.new(value).realpath}" if File.symlink?(value)
+        s << " => #{Pathname.new(value).realpath}" if value.present? && File.symlink?(value)
       end
       s.freeze
       f.puts s
diff --git a/Library/Homebrew/cmd/--env.rb b/Library/Homebrew/cmd/--env.rb
index f9c12119d9..a442e6ad4b 100644
--- a/Library/Homebrew/cmd/--env.rb
+++ b/Library/Homebrew/cmd/--env.rb
@@ -51,7 +51,7 @@ module Homebrew
     if shell.nil?
       BuildEnvironment.dump ENV
     else
-      BuildEnvironment.keys(ENV).each do |key|
+      BuildEnvironment.keys(ENV.to_h).each do |key|
         puts Utils::Shell.export_value(key, ENV.fetch(key), shell)
       end
     end
diff --git a/Library/Homebrew/exceptions.rb b/Library/Homebrew/exceptions.rb
index 6f83563226..4641684b08 100644
--- a/Library/Homebrew/exceptions.rb
+++ b/Library/Homebrew/exceptions.rb
@@ -466,9 +466,19 @@ end
 
 # Raised when an error occurs during a formula build.
 class BuildError < RuntimeError
+  extend T::Sig
+
   attr_reader :cmd, :args, :env
   attr_accessor :formula, :options
 
+  sig {
+    params(
+      formula: T.nilable(Formula),
+      cmd:     T.any(String, Pathname),
+      args:    T::Array[T.any(String, Pathname, Integer)],
+      env:     T::Hash[String, T.untyped],
+    ).void
+  }
   def initialize(formula, cmd, args, env)
     @formula = formula
     @cmd = cmd
@@ -478,10 +488,12 @@ class BuildError < RuntimeError
     super "Failed executing: #{cmd} #{pretty_args}".strip
   end
 
+  sig { returns(T::Array[T.untyped]) }
   def issues
     @issues ||= fetch_issues
   end
 
+  sig { returns(T::Array[T.untyped]) }
   def fetch_issues
     GitHub.issues_for_formula(formula.name, tap: formula.tap, state: "open")
   rescue GitHub::API::RateLimitExceededError => e
@@ -489,6 +501,7 @@ class BuildError < RuntimeError
     []
   end
 
+  sig { params(verbose: T::Boolean).void }
   def dump(verbose: false)
     puts
 
diff --git a/Library/Homebrew/formula.rb b/Library/Homebrew/formula.rb
index 44d7190ff3..be6c3b6b34 100644
--- a/Library/Homebrew/formula.rb
+++ b/Library/Homebrew/formula.rb
@@ -2219,7 +2219,7 @@ class Formula
   def inreplace(paths, before = nil, after = nil, audit_result = true) # rubocop:disable Style/OptionalBooleanParameter
     super(paths, before, after, audit_result)
   rescue Utils::Inreplace::Error
-    raise BuildError.new(self, "inreplace", paths, nil)
+    raise BuildError.new(self, "inreplace", paths, {})
   end
 
   protected