CompilerSelector: raise when no compatible compiler

This replaces the old behaviour of falling back to the original
compiler with no messaging.

Fixes Homebrew/homebrew#19170.
Fixes mistydemeo/tigerbrew#45.

1 files changed, 20 insertions, 0 deletions

diff --git a/Library/Homebrew/exceptions.rb b/Library/Homebrew/exceptions.rb
index 4f1fafdce..0dbdb8b1d 100644
--- a/Library/Homebrew/exceptions.rb
+++ b/Library/Homebrew/exceptions.rb
@@ -160,6 +160,26 @@ class BuildError < Homebrew::InstallationError
   end
 end
 
+# raised by CompilerSelector if the formula fails with all of
+# the compilers available on the user's system
+class CompilerSelectionError < StandardError
+  def message
+    if MacOS.version > :tiger then <<-EOS.undent
+      This formula cannot be built with any available compilers.
+      To install this formula, you may need to:
+        brew tap homebrew/dupes
+        brew install apple-gcc42
+      EOS
+    # tigerbrew has a separate apple-gcc42 for Xcode 2.5
+    else <<-EOS.undent
+      This formula cannot be built with any available compilers.
+      To install this formula, you need to:
+        brew install apple-gcc42
+      EOS
+    end
+  end
+end
+
 # raised in CurlDownloadStrategy.fetch
 class CurlDownloadStrategyError < RuntimeError
 end