librustc_back: convert fn target() to return Result

Change all the target generation functions to return a Result<Target,
String> so that targets that are unable to be instantiated can be
expressed as an Err instead of a panic!(). This should improve #33497 as
well.

45 files changed, 212 insertions, 202 deletions

diff --git a/src/librustc_back/target/aarch64_apple_ios.rs b/src/librustc_back/target/aarch64_apple_ios.rs
index 481338d1cee..6530ccb0630 100644
--- a/src/librustc_back/target/aarch64_apple_ios.rs
+++ b/src/librustc_back/target/aarch64_apple_ios.rs
@@ -8,11 +8,12 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::{Target, TargetOptions};
+use target::{Target, TargetOptions, TargetResult};
 use super::apple_ios_base::{opts, Arch};
 
-pub fn target() -> Target {
-    Target {
+pub fn target() -> TargetResult {
+    let base = try!(opts(Arch::Arm64));
+    Ok(Target {
         llvm_target: "arm64-apple-ios".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),
@@ -25,7 +26,7 @@ pub fn target() -> Target {
             features: "+neon,+fp-armv8,+cyclone".to_string(),
             eliminate_frame_pointer: false,
             max_atomic_width: 128,
-            .. opts(Arch::Arm64)
+            .. base
         },
-    }
+    })
 }
diff --git a/src/librustc_back/target/aarch64_linux_android.rs b/src/librustc_back/target/aarch64_linux_android.rs
index 81be546e0c8..307823137a7 100644
--- a/src/librustc_back/target/aarch64_linux_android.rs
+++ b/src/librustc_back/target/aarch64_linux_android.rs
@@ -8,15 +8,15 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::android_base::opts();
     base.max_atomic_width = 128;
     // As documented in http://developer.android.com/ndk/guides/cpu-features.html
     // the neon (ASIMD) and FP must exist on all android aarch64 targets.
     base.features = "+neon,+fp-armv8".to_string();
-    Target {
+    Ok(Target {
         llvm_target: "aarch64-linux-android".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),
@@ -26,5 +26,5 @@ pub fn target() -> Target {
         target_env: "".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/aarch64_unknown_linux_gnu.rs b/src/librustc_back/target/aarch64_unknown_linux_gnu.rs
index aec1bae60c8..14d0c8bedec 100644
--- a/src/librustc_back/target/aarch64_unknown_linux_gnu.rs
+++ b/src/librustc_back/target/aarch64_unknown_linux_gnu.rs
@@ -8,12 +8,12 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::linux_base::opts();
     base.max_atomic_width = 128;
-    Target {
+    Ok(Target {
         llvm_target: "aarch64-unknown-linux-gnu".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),
@@ -23,5 +23,5 @@ pub fn target() -> Target {
         target_os: "linux".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/apple_ios_base.rs b/src/librustc_back/target/apple_ios_base.rs
index d182fd96056..8bd9feabdbe 100644
--- a/src/librustc_back/target/apple_ios_base.rs
+++ b/src/librustc_back/target/apple_ios_base.rs
@@ -36,7 +36,7 @@ impl Arch {
     }
 }
 
-pub fn get_sdk_root(sdk_name: &str) -> String {
+pub fn get_sdk_root(sdk_name: &str) -> Result<String, String> {
     let res = Command::new("xcrun")
                       .arg("--show-sdk-path")
                       .arg("-sdk")
@@ -55,12 +55,12 @@ pub fn get_sdk_root(sdk_name: &str) -> String {
                       });
 
     match res {
-        Ok(output) => output.trim().to_string(),
-        Err(e) => panic!("failed to get {} SDK path: {}", sdk_name, e)
+        Ok(output) => Ok(output.trim().to_string()),
+        Err(e) => Err(format!("failed to get {} SDK path: {}", sdk_name, e))
     }
 }
 
-fn pre_link_args(arch: Arch) -> Vec<String> {
+fn build_pre_link_args(arch: Arch) -> Result<Vec<String>, String> {
     let sdk_name = match arch {
         Armv7 | Armv7s | Arm64 => "iphoneos",
         I386 | X86_64 => "iphonesimulator"
@@ -68,8 +68,10 @@ fn pre_link_args(arch: Arch) -> Vec<String> {
 
     let arch_name = arch.to_string();
 
-    vec!["-arch".to_string(), arch_name.to_string(),
-         "-Wl,-syslibroot".to_string(), get_sdk_root(sdk_name)]
+    let sdk_root = try!(get_sdk_root(sdk_name));
+
+    Ok(vec!["-arch".to_string(), arch_name.to_string(),
+         "-Wl,-syslibroot".to_string(), sdk_root])
 }
 
 fn target_cpu(arch: Arch) -> String {
@@ -82,13 +84,14 @@ fn target_cpu(arch: Arch) -> String {
     }.to_string()
 }
 
-pub fn opts(arch: Arch) -> TargetOptions {
-    TargetOptions {
+pub fn opts(arch: Arch) -> Result<TargetOptions, String> {
+    let pre_link_args = try!(build_pre_link_args(arch));
+    Ok(TargetOptions {
         cpu: target_cpu(arch),
         dynamic_linking: false,
         executables: true,
-        pre_link_args: pre_link_args(arch),
+        pre_link_args: pre_link_args,
         has_elf_tls: false,
         .. super::apple_base::opts()
-    }
+    })
 }
diff --git a/src/librustc_back/target/arm_linux_androideabi.rs b/src/librustc_back/target/arm_linux_androideabi.rs
index e1b170422c6..f3a18b13c67 100644
--- a/src/librustc_back/target/arm_linux_androideabi.rs
+++ b/src/librustc_back/target/arm_linux_androideabi.rs
@@ -8,14 +8,14 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::android_base::opts();
     base.features = "+v7,+vfp3,+d16".to_string();
     base.max_atomic_width = 64;
 
-    Target {
+    Ok(Target {
         llvm_target: "arm-linux-androideabi".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -25,5 +25,5 @@ pub fn target() -> Target {
         target_env: "".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/arm_unknown_linux_gnueabi.rs b/src/librustc_back/target/arm_unknown_linux_gnueabi.rs
index 60c4a7c3c90..e666a8460e5 100644
--- a/src/librustc_back/target/arm_unknown_linux_gnueabi.rs
+++ b/src/librustc_back/target/arm_unknown_linux_gnueabi.rs
@@ -8,12 +8,12 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::{Target, TargetOptions};
+use target::{Target, TargetOptions, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::linux_base::opts();
     base.max_atomic_width = 64;
-    Target {
+    Ok(Target {
         llvm_target: "arm-unknown-linux-gnueabi".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -27,5 +27,5 @@ pub fn target() -> Target {
             features: "+v6".to_string(),
             .. base
         },
-    }
+    })
 }
diff --git a/src/librustc_back/target/arm_unknown_linux_gnueabihf.rs b/src/librustc_back/target/arm_unknown_linux_gnueabihf.rs
index 72128e30641..d65c89abc20 100644
--- a/src/librustc_back/target/arm_unknown_linux_gnueabihf.rs
+++ b/src/librustc_back/target/arm_unknown_linux_gnueabihf.rs
@@ -8,12 +8,12 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::{Target, TargetOptions};
+use target::{Target, TargetOptions, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::linux_base::opts();
     base.max_atomic_width = 64;
-    Target {
+    Ok(Target {
         llvm_target: "arm-unknown-linux-gnueabihf".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -27,5 +27,5 @@ pub fn target() -> Target {
             features: "+v6,+vfp2".to_string(),
             .. base
         }
-    }
+    })
 }
diff --git a/src/librustc_back/target/armv7_apple_ios.rs b/src/librustc_back/target/armv7_apple_ios.rs
index a2486a1330a..a806204d0a6 100644
--- a/src/librustc_back/target/armv7_apple_ios.rs
+++ b/src/librustc_back/target/armv7_apple_ios.rs
@@ -8,11 +8,12 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::{Target, TargetOptions};
+use target::{Target, TargetOptions, TargetResult};
 use super::apple_ios_base::{opts, Arch};
 
-pub fn target() -> Target {
-    Target {
+pub fn target() -> TargetResult {
+    let base = try!(opts(Arch::Armv7));
+    Ok(Target {
         llvm_target: "armv7-apple-ios".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -24,7 +25,7 @@ pub fn target() -> Target {
         options: TargetOptions {
             features: "+v7,+vfp3,+neon".to_string(),
             max_atomic_width: 64,
-            .. opts(Arch::Armv7)
+            .. base
         }
-    }
+    })
 }
diff --git a/src/librustc_back/target/armv7_linux_androideabi.rs b/src/librustc_back/target/armv7_linux_androideabi.rs
index fd8f35da16f..1c59262e041 100644
--- a/src/librustc_back/target/armv7_linux_androideabi.rs
+++ b/src/librustc_back/target/armv7_linux_androideabi.rs
@@ -8,14 +8,14 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::android_base::opts();
     base.features = "+v7,+thumb2,+vfp3,+d16".to_string();
     base.max_atomic_width = 64;
 
-    Target {
+    Ok(Target {
         llvm_target: "armv7-none-linux-android".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -25,5 +25,5 @@ pub fn target() -> Target {
         target_env: "".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/armv7_unknown_linux_gnueabihf.rs b/src/librustc_back/target/armv7_unknown_linux_gnueabihf.rs
index 7bcca3a3934..52269f0cd4a 100644
--- a/src/librustc_back/target/armv7_unknown_linux_gnueabihf.rs
+++ b/src/librustc_back/target/armv7_unknown_linux_gnueabihf.rs
@@ -8,11 +8,11 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::{Target, TargetOptions};
+use target::{Target, TargetOptions, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let base = super::linux_base::opts();
-    Target {
+    Ok(Target {
         llvm_target: "armv7-unknown-linux-gnueabihf".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -28,6 +28,6 @@ pub fn target() -> Target {
             max_atomic_width: 64,
             .. base
         }
-    }
+    })
 }
 
diff --git a/src/librustc_back/target/armv7s_apple_ios.rs b/src/librustc_back/target/armv7s_apple_ios.rs
index e5379aa1b42..aaa3570fa62 100644
--- a/src/librustc_back/target/armv7s_apple_ios.rs
+++ b/src/librustc_back/target/armv7s_apple_ios.rs
@@ -8,11 +8,12 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::{Target, TargetOptions};
+use target::{Target, TargetOptions, TargetResult};
 use super::apple_ios_base::{opts, Arch};
 
-pub fn target() -> Target {
-    Target {
+pub fn target() -> TargetResult {
+    let base = try!(opts(Arch::Armv7s));
+    Ok(Target {
         llvm_target: "armv7s-apple-ios".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -24,7 +25,7 @@ pub fn target() -> Target {
         options: TargetOptions {
             features: "+v7,+vfp4,+neon".to_string(),
             max_atomic_width: 64,
-            .. opts(Arch::Armv7s)
+            .. base
         }
-    }
+    })
 }
diff --git a/src/librustc_back/target/asmjs_unknown_emscripten.rs b/src/librustc_back/target/asmjs_unknown_emscripten.rs
index e6200177944..07eb191471c 100644
--- a/src/librustc_back/target/asmjs_unknown_emscripten.rs
+++ b/src/librustc_back/target/asmjs_unknown_emscripten.rs
@@ -10,7 +10,7 @@
 
 use super::{Target, TargetOptions};
 
-pub fn target() -> Target {
+pub fn target() -> Result<Target, String> {
     let opts = TargetOptions {
         linker: "emcc".to_string(),
         ar: "emar".to_string(),
@@ -25,7 +25,7 @@ pub fn target() -> Target {
         max_atomic_width: 32,
         .. Default::default()
     };
-    Target {
+    Ok(Target {
         llvm_target: "asmjs-unknown-emscripten".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -35,5 +35,5 @@ pub fn target() -> Target {
         data_layout: "e-p:32:32-i64:64-v128:32:128-n32-S128".to_string(),
         arch: "asmjs".to_string(),
         options: opts,
-    }
+    })
 }
diff --git a/src/librustc_back/target/i386_apple_ios.rs b/src/librustc_back/target/i386_apple_ios.rs
index cf4020eeb58..f391d4118ea 100644
--- a/src/librustc_back/target/i386_apple_ios.rs
+++ b/src/librustc_back/target/i386_apple_ios.rs
@@ -8,11 +8,12 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::{Target, TargetOptions};
+use target::{Target, TargetOptions, TargetResult};
 use super::apple_ios_base::{opts, Arch};
 
-pub fn target() -> Target {
-    Target {
+pub fn target() -> TargetResult {
+    let base = try!(opts(Arch::I386));
+    Ok(Target {
         llvm_target: "i386-apple-ios".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -23,7 +24,7 @@ pub fn target() -> Target {
         target_vendor: "apple".to_string(),
         options: TargetOptions {
             max_atomic_width: 64,
-            .. opts(Arch::I386)
+            .. base
         }
-    }
+    })
 }
diff --git a/src/librustc_back/target/i586_pc_windows_msvc.rs b/src/librustc_back/target/i586_pc_windows_msvc.rs
index 12bed370eae..445ee6c4122 100644
--- a/src/librustc_back/target/i586_pc_windows_msvc.rs
+++ b/src/librustc_back/target/i586_pc_windows_msvc.rs
@@ -8,11 +8,11 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::TargetResult;
 
-pub fn target() -> Target {
-    let mut base = super::i686_pc_windows_msvc::target();
+pub fn target() -> TargetResult {
+    let mut base = try!(super::i686_pc_windows_msvc::target());
     base.options.cpu = "pentium".to_string();
     base.llvm_target = "i586-pc-windows-msvc".to_string();
-    return base
+    Ok(base)
 }
diff --git a/src/librustc_back/target/i586_unknown_linux_gnu.rs b/src/librustc_back/target/i586_unknown_linux_gnu.rs
index 6eb64556381..1ca8606149b 100644
--- a/src/librustc_back/target/i586_unknown_linux_gnu.rs
+++ b/src/librustc_back/target/i586_unknown_linux_gnu.rs
@@ -8,11 +8,11 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::TargetResult;
 
-pub fn target() -> Target {
-    let mut base = super::i686_unknown_linux_gnu::target();
+pub fn target() -> TargetResult {
+    let mut base = try!(super::i686_unknown_linux_gnu::target());
     base.options.cpu = "pentium".to_string();
     base.llvm_target = "i586-unknown-linux-gnu".to_string();
-    return base
+    Ok(base)
 }
diff --git a/src/librustc_back/target/i686_apple_darwin.rs b/src/librustc_back/target/i686_apple_darwin.rs
index 302691e9a59..4876a3489d4 100644
--- a/src/librustc_back/target/i686_apple_darwin.rs
+++ b/src/librustc_back/target/i686_apple_darwin.rs
@@ -8,15 +8,15 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::apple_base::opts();
     base.cpu = "yonah".to_string();
     base.max_atomic_width = 64;
     base.pre_link_args.push("-m32".to_string());
 
-    Target {
+    Ok(Target {
         llvm_target: "i686-apple-darwin".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -26,5 +26,5 @@ pub fn target() -> Target {
         target_env: "".to_string(),
         target_vendor: "apple".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/i686_linux_android.rs b/src/librustc_back/target/i686_linux_android.rs
index 2376de12398..1de629238a1 100644
--- a/src/librustc_back/target/i686_linux_android.rs
+++ b/src/librustc_back/target/i686_linux_android.rs
@@ -8,9 +8,9 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::android_base::opts();
 
     base.max_atomic_width = 64;
@@ -19,7 +19,7 @@ pub fn target() -> Target {
     base.cpu = "pentiumpro".to_string();
     base.features = "+mmx,+sse,+sse2,+sse3,+ssse3".to_string();
 
-    Target {
+    Ok(Target {
         llvm_target: "i686-linux-android".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -29,5 +29,5 @@ pub fn target() -> Target {
         target_env: "".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/i686_pc_windows_gnu.rs b/src/librustc_back/target/i686_pc_windows_gnu.rs
index c2cc624c9f9..2c19b8109c3 100644
--- a/src/librustc_back/target/i686_pc_windows_gnu.rs
+++ b/src/librustc_back/target/i686_pc_windows_gnu.rs
@@ -8,9 +8,9 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::windows_base::opts();
     base.cpu = "pentium4".to_string();
     base.max_atomic_width = 64;
@@ -19,7 +19,7 @@ pub fn target() -> Target {
     // space available to x86 Windows binaries on x86_64.
     base.pre_link_args.push("-Wl,--large-address-aware".to_string());
 
-    Target {
+    Ok(Target {
         llvm_target: "i686-pc-windows-gnu".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -29,5 +29,5 @@ pub fn target() -> Target {
         target_env: "gnu".to_string(),
         target_vendor: "pc".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/i686_pc_windows_msvc.rs b/src/librustc_back/target/i686_pc_windows_msvc.rs
index 8c1bacc2807..cb02fcc308c 100644
--- a/src/librustc_back/target/i686_pc_windows_msvc.rs
+++ b/src/librustc_back/target/i686_pc_windows_msvc.rs
@@ -8,9 +8,9 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::windows_msvc_base::opts();
     base.cpu = "pentium4".to_string();
     base.max_atomic_width = 64;
@@ -24,7 +24,7 @@ pub fn target() -> Target {
     // https://msdn.microsoft.com/en-us/library/9a89h429.aspx
     base.pre_link_args.push("/SAFESEH".to_string());
 
-    Target {
+    Ok(Target {
         llvm_target: "i686-pc-windows-msvc".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -34,5 +34,5 @@ pub fn target() -> Target {
         target_env: "msvc".to_string(),
         target_vendor: "pc".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/i686_unknown_dragonfly.rs b/src/librustc_back/target/i686_unknown_dragonfly.rs
index 6446ac45f7d..f96ec004b48 100644
--- a/src/librustc_back/target/i686_unknown_dragonfly.rs
+++ b/src/librustc_back/target/i686_unknown_dragonfly.rs
@@ -8,15 +8,15 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::dragonfly_base::opts();
     base.cpu = "pentium4".to_string();
     base.max_atomic_width = 64;
     base.pre_link_args.push("-m32".to_string());
 
-    Target {
+    Ok(Target {
         llvm_target: "i686-unknown-dragonfly".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -26,5 +26,5 @@ pub fn target() -> Target {
         target_env: "".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/i686_unknown_freebsd.rs b/src/librustc_back/target/i686_unknown_freebsd.rs
index a7903d5db64..3489ecfe614 100644
--- a/src/librustc_back/target/i686_unknown_freebsd.rs
+++ b/src/librustc_back/target/i686_unknown_freebsd.rs
@@ -8,15 +8,15 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::freebsd_base::opts();
     base.cpu = "pentium4".to_string();
     base.max_atomic_width = 64;
     base.pre_link_args.push("-m32".to_string());
 
-    Target {
+    Ok(Target {
         llvm_target: "i686-unknown-freebsd".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -26,5 +26,5 @@ pub fn target() -> Target {
         target_env: "".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/i686_unknown_linux_gnu.rs b/src/librustc_back/target/i686_unknown_linux_gnu.rs
index 7813d557076..f2e865c015e 100644
--- a/src/librustc_back/target/i686_unknown_linux_gnu.rs
+++ b/src/librustc_back/target/i686_unknown_linux_gnu.rs
@@ -8,15 +8,15 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::linux_base::opts();
     base.cpu = "pentium4".to_string();
     base.max_atomic_width = 64;
     base.pre_link_args.push("-m32".to_string());
 
-    Target {
+    Ok(Target {
         llvm_target: "i686-unknown-linux-gnu".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -26,5 +26,5 @@ pub fn target() -> Target {
         target_env: "gnu".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/i686_unknown_linux_musl.rs b/src/librustc_back/target/i686_unknown_linux_musl.rs
index 52744295837..a0a8de46e2f 100644
--- a/src/librustc_back/target/i686_unknown_linux_musl.rs
+++ b/src/librustc_back/target/i686_unknown_linux_musl.rs
@@ -8,16 +8,16 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::linux_musl_base::opts();
     base.cpu = "pentium4".to_string();
     base.max_atomic_width = 64;
     base.pre_link_args.push("-m32".to_string());
     base.pre_link_args.push("-Wl,-melf_i386".to_string());
 
-    Target {
+    Ok(Target {
         llvm_target: "i686-unknown-linux-musl".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -27,5 +27,5 @@ pub fn target() -> Target {
         target_env: "musl".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/le32_unknown_nacl.rs b/src/librustc_back/target/le32_unknown_nacl.rs
index f4f0262d476..25132f8a044 100644
--- a/src/librustc_back/target/le32_unknown_nacl.rs
+++ b/src/librustc_back/target/le32_unknown_nacl.rs
@@ -8,9 +8,9 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use super::{Target, TargetOptions};
+use super::{Target, TargetOptions, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let opts = TargetOptions {
         linker: "pnacl-clang".to_string(),
         ar: "pnacl-ar".to_string(),
@@ -28,7 +28,7 @@ pub fn target() -> Target {
         max_atomic_width: 32,
         .. Default::default()
     };
-    Target {
+    Ok(Target {
         llvm_target: "le32-unknown-nacl".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -38,5 +38,5 @@ pub fn target() -> Target {
         data_layout: "e-i64:64:64-p:32:32:32-v128:32:32".to_string(),
         arch: "le32".to_string(),
         options: opts,
-    }
+    })
 }
diff --git a/src/librustc_back/target/mips_unknown_linux_gnu.rs b/src/librustc_back/target/mips_unknown_linux_gnu.rs
index ceb17e53a55..ab967f6b40f 100644
--- a/src/librustc_back/target/mips_unknown_linux_gnu.rs
+++ b/src/librustc_back/target/mips_unknown_linux_gnu.rs
@@ -8,10 +8,10 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::{Target, TargetOptions};
+use target::{Target, TargetOptions, TargetResult};
 
-pub fn target() -> Target {
-    Target {
+pub fn target() -> TargetResult {
+    Ok(Target {
         llvm_target: "mips-unknown-linux-gnu".to_string(),
         target_endian: "big".to_string(),
         target_pointer_width: "32".to_string(),
@@ -26,5 +26,5 @@ pub fn target() -> Target {
             max_atomic_width: 32,
             ..super::linux_base::opts()
         },
-    }
+    })
 }
diff --git a/src/librustc_back/target/mips_unknown_linux_musl.rs b/src/librustc_back/target/mips_unknown_linux_musl.rs
index 35366659d58..4a69bce53bc 100644
--- a/src/librustc_back/target/mips_unknown_linux_musl.rs
+++ b/src/librustc_back/target/mips_unknown_linux_musl.rs
@@ -8,10 +8,10 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::{Target, TargetOptions};
+use target::{Target, TargetOptions, TargetResult};
 
-pub fn target() -> Target {
-    Target {
+pub fn target() -> TargetResult {
+    Ok(Target {
         llvm_target: "mips-unknown-linux-musl".to_string(),
         target_endian: "big".to_string(),
         target_pointer_width: "32".to_string(),
@@ -26,5 +26,5 @@ pub fn target() -> Target {
             max_atomic_width: 32,
             ..super::linux_base::opts()
         }
-    }
+    })
 }
diff --git a/src/librustc_back/target/mipsel_unknown_linux_gnu.rs b/src/librustc_back/target/mipsel_unknown_linux_gnu.rs
index ac1536b3d00..b66fb62cd59 100644
--- a/src/librustc_back/target/mipsel_unknown_linux_gnu.rs
+++ b/src/librustc_back/target/mipsel_unknown_linux_gnu.rs
@@ -8,10 +8,10 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::{Target, TargetOptions};
+use target::{Target, TargetOptions, TargetResult};
 
-pub fn target() -> Target {
-    Target {
+pub fn target() -> TargetResult {
+    Ok(Target {
         llvm_target: "mipsel-unknown-linux-gnu".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -27,5 +27,5 @@ pub fn target() -> Target {
             max_atomic_width: 32,
             ..super::linux_base::opts()
         },
-    }
+    })
 }
diff --git a/src/librustc_back/target/mipsel_unknown_linux_musl.rs b/src/librustc_back/target/mipsel_unknown_linux_musl.rs
index a9ea52c4278..24d1a66ec2d 100644
--- a/src/librustc_back/target/mipsel_unknown_linux_musl.rs
+++ b/src/librustc_back/target/mipsel_unknown_linux_musl.rs
@@ -8,10 +8,10 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::{Target, TargetOptions};
+use target::{Target, TargetOptions, TargetResult};
 
-pub fn target() -> Target {
-    Target {
+pub fn target() -> TargetResult {
+    Ok(Target {
         llvm_target: "mipsel-unknown-linux-musl".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -26,5 +26,5 @@ pub fn target() -> Target {
             max_atomic_width: 32,
             ..super::linux_base::opts()
         }
-    }
+    })
 }
diff --git a/src/librustc_back/target/mod.rs b/src/librustc_back/target/mod.rs
index 067885c92fd..4849a76e11d 100644
--- a/src/librustc_back/target/mod.rs
+++ b/src/librustc_back/target/mod.rs
@@ -64,6 +64,8 @@ mod solaris_base;
 mod windows_base;
 mod windows_msvc_base;
 
+pub type TargetResult = Result<Target, String>;
+
 macro_rules! supported_targets {
     ( $(($triple:expr, $module:ident)),+ ) => (
         $(mod $module;)*
@@ -71,17 +73,17 @@ macro_rules! supported_targets {
         /// List of supported targets
         pub const TARGETS: &'static [&'static str] = &[$($triple),*];
 
-        fn load_specific(target: &str) -> Option<Target> {
+        fn load_specific(target: &str) -> TargetResult {
             match target {
                 $(
                     $triple => {
-                        let mut t = $module::target();
+                        let mut t = try!($module::target());
                         t.options.is_builtin = true;
                         debug!("Got builtin target: {:?}", t);
-                        Some(t)
+                        Ok(t)
                     },
                 )+
-                _ => None
+                _ => Err(format!("Unable to find target: {}", target))
             }
         }
     )
@@ -364,7 +366,7 @@ impl Target {
     }
 
     /// Load a target descriptor from a JSON object.
-    pub fn from_json(obj: Json) -> Target {
+    pub fn from_json(obj: Json) -> TargetResult {
         // While ugly, this code must remain this way to retain
         // compatibility with existing JSON fields and the internal
         // expected naming of the Target and TargetOptions structs.
@@ -376,9 +378,9 @@ impl Target {
             match obj.find(name)
                      .map(|s| s.as_string())
                      .and_then(|os| os.map(|s| s.to_string())) {
-                Some(val) => val,
+                Some(val) => Ok(val),
                 None => {
-                    panic!("Field {} in target specification is required", name)
+                    return Err(format!("Field {} in target specification is required", name))
                 }
             }
         };
@@ -390,12 +392,12 @@ impl Target {
         };
 
         let mut base = Target {
-            llvm_target: get_req_field("llvm-target"),
-            target_endian: get_req_field("target-endian"),
-            target_pointer_width: get_req_field("target-pointer-width"),
-            data_layout: get_req_field("data-layout"),
-            arch: get_req_field("arch"),
-            target_os: get_req_field("os"),
+            llvm_target: try!(get_req_field("llvm-target")),
+            target_endian: try!(get_req_field("target-endian")),
+            target_pointer_width: try!(get_req_field("target-pointer-width")),
+            data_layout: try!(get_req_field("data-layout")),
+            arch: try!(get_req_field("arch")),
+            target_os: try!(get_req_field("os")),
             target_env: get_opt_field("env", ""),
             target_vendor: get_opt_field("vendor", "unknown"),
             options: Default::default(),
@@ -483,7 +485,7 @@ impl Target {
         key!(obj_is_bitcode, bool);
         key!(max_atomic_width, u64);
 
-        base
+        Ok(base)
     }
 
     /// Search RUST_TARGET_PATH for a JSON file specifying the given target
@@ -506,10 +508,10 @@ impl Target {
             f.read_to_end(&mut contents).map_err(|e| e.to_string())?;
             let obj = json::from_reader(&mut &contents[..])
                            .map_err(|e| e.to_string())?;
-            Ok(Target::from_json(obj))
+            Target::from_json(obj)
         }
 
-        if let Some(t) = load_specific(target) {
+        if let Ok(t) = load_specific(target) {
             return Ok(t)
         }
 
diff --git a/src/librustc_back/target/powerpc64_unknown_linux_gnu.rs b/src/librustc_back/target/powerpc64_unknown_linux_gnu.rs
index be4be8e6fc9..1c04e763417 100644
--- a/src/librustc_back/target/powerpc64_unknown_linux_gnu.rs
+++ b/src/librustc_back/target/powerpc64_unknown_linux_gnu.rs
@@ -8,15 +8,15 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::linux_base::opts();
     base.cpu = "ppc64".to_string();
     base.pre_link_args.push("-m64".to_string());
     base.max_atomic_width = 64;
 
-    Target {
+    Ok(Target {
         llvm_target: "powerpc64-unknown-linux-gnu".to_string(),
         target_endian: "big".to_string(),
         target_pointer_width: "64".to_string(),
@@ -26,5 +26,5 @@ pub fn target() -> Target {
         target_env: "gnu".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/powerpc64le_unknown_linux_gnu.rs b/src/librustc_back/target/powerpc64le_unknown_linux_gnu.rs
index b0a81ce7ec5..906e28d2f20 100644
--- a/src/librustc_back/target/powerpc64le_unknown_linux_gnu.rs
+++ b/src/librustc_back/target/powerpc64le_unknown_linux_gnu.rs
@@ -8,15 +8,15 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::linux_base::opts();
     base.cpu = "ppc64le".to_string();
     base.pre_link_args.push("-m64".to_string());
     base.max_atomic_width = 64;
 
-    Target {
+    Ok(Target {
         llvm_target: "powerpc64le-unknown-linux-gnu".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),
@@ -26,5 +26,5 @@ pub fn target() -> Target {
         target_env: "gnu".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/powerpc_unknown_linux_gnu.rs b/src/librustc_back/target/powerpc_unknown_linux_gnu.rs
index aea57dc4b7f..aebf9cd6871 100644
--- a/src/librustc_back/target/powerpc_unknown_linux_gnu.rs
+++ b/src/librustc_back/target/powerpc_unknown_linux_gnu.rs
@@ -8,14 +8,14 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::linux_base::opts();
     base.pre_link_args.push("-m32".to_string());
     base.max_atomic_width = 32;
 
-    Target {
+    Ok(Target {
         llvm_target: "powerpc-unknown-linux-gnu".to_string(),
         target_endian: "big".to_string(),
         target_pointer_width: "32".to_string(),
@@ -25,5 +25,5 @@ pub fn target() -> Target {
         target_env: "gnu".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/x86_64_apple_darwin.rs b/src/librustc_back/target/x86_64_apple_darwin.rs
index 5542c9120a4..65e4b1400fc 100644
--- a/src/librustc_back/target/x86_64_apple_darwin.rs
+++ b/src/librustc_back/target/x86_64_apple_darwin.rs
@@ -8,16 +8,16 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::apple_base::opts();
     base.cpu = "core2".to_string();
     base.max_atomic_width = 128; // core2 support cmpxchg16b
     base.eliminate_frame_pointer = false;
     base.pre_link_args.push("-m64".to_string());
 
-    Target {
+    Ok(Target {
         llvm_target: "x86_64-apple-darwin".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),
@@ -27,5 +27,5 @@ pub fn target() -> Target {
         target_env: "".to_string(),
         target_vendor: "apple".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/x86_64_apple_ios.rs b/src/librustc_back/target/x86_64_apple_ios.rs
index 8638241f861..4afc9bcb946 100644
--- a/src/librustc_back/target/x86_64_apple_ios.rs
+++ b/src/librustc_back/target/x86_64_apple_ios.rs
@@ -8,11 +8,12 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::{Target, TargetOptions};
+use target::{Target, TargetOptions, TargetResult};
 use super::apple_ios_base::{opts, Arch};
 
-pub fn target() -> Target {
-    Target {
+pub fn target() -> TargetResult {
+    let base = try!(opts(Arch::X86_64));
+    Ok(Target {
         llvm_target: "x86_64-apple-ios".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),
@@ -23,7 +24,7 @@ pub fn target() -> Target {
         target_vendor: "apple".to_string(),
         options: TargetOptions {
             max_atomic_width: 64,
-            .. opts(Arch::X86_64)
+            .. base
         }
-    }
+    })
 }
diff --git a/src/librustc_back/target/x86_64_pc_windows_gnu.rs b/src/librustc_back/target/x86_64_pc_windows_gnu.rs
index e243054d023..086e0e6bf4f 100644
--- a/src/librustc_back/target/x86_64_pc_windows_gnu.rs
+++ b/src/librustc_back/target/x86_64_pc_windows_gnu.rs
@@ -8,15 +8,15 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::windows_base::opts();
     base.cpu = "x86-64".to_string();
     base.pre_link_args.push("-m64".to_string());
     base.max_atomic_width = 64;
 
-    Target {
+    Ok(Target {
         llvm_target: "x86_64-pc-windows-gnu".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),
@@ -26,5 +26,5 @@ pub fn target() -> Target {
         target_env: "gnu".to_string(),
         target_vendor: "pc".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/x86_64_pc_windows_msvc.rs b/src/librustc_back/target/x86_64_pc_windows_msvc.rs
index a23a807a025..064f06e9b31 100644
--- a/src/librustc_back/target/x86_64_pc_windows_msvc.rs
+++ b/src/librustc_back/target/x86_64_pc_windows_msvc.rs
@@ -8,14 +8,14 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::windows_msvc_base::opts();
     base.cpu = "x86-64".to_string();
     base.max_atomic_width = 64;
 
-    Target {
+    Ok(Target {
         llvm_target: "x86_64-pc-windows-msvc".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),
@@ -25,5 +25,5 @@ pub fn target() -> Target {
         target_env: "msvc".to_string(),
         target_vendor: "pc".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/x86_64_rumprun_netbsd.rs b/src/librustc_back/target/x86_64_rumprun_netbsd.rs
index af5d21c4d93..537d15f4603 100644
--- a/src/librustc_back/target/x86_64_rumprun_netbsd.rs
+++ b/src/librustc_back/target/x86_64_rumprun_netbsd.rs
@@ -8,9 +8,9 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::netbsd_base::opts();
     base.pre_link_args.push("-m64".to_string());
     base.linker = "x86_64-rumprun-netbsd-gcc".to_string();
@@ -24,7 +24,7 @@ pub fn target() -> Target {
     base.no_default_libraries = false;
     base.exe_allocation_crate = "alloc_system".to_string();
 
-    Target {
+    Ok(Target {
         llvm_target: "x86_64-rumprun-netbsd".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),
@@ -34,5 +34,5 @@ pub fn target() -> Target {
         target_env: "".to_string(),
         target_vendor: "rumprun".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/x86_64_sun_solaris.rs b/src/librustc_back/target/x86_64_sun_solaris.rs
index 8f2c905cf2e..2a1feb937f7 100644
--- a/src/librustc_back/target/x86_64_sun_solaris.rs
+++ b/src/librustc_back/target/x86_64_sun_solaris.rs
@@ -8,15 +8,15 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::solaris_base::opts();
     base.pre_link_args.push("-m64".to_string());
     base.cpu = "x86-64".to_string();
     base.max_atomic_width = 64;
 
-    Target {
+    Ok(Target {
         llvm_target: "x86_64-pc-solaris".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),
@@ -26,5 +26,5 @@ pub fn target() -> Target {
         target_env: "".to_string(),
         target_vendor: "sun".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/x86_64_unknown_bitrig.rs b/src/librustc_back/target/x86_64_unknown_bitrig.rs
index 87753da540a..81710b99b80 100644
--- a/src/librustc_back/target/x86_64_unknown_bitrig.rs
+++ b/src/librustc_back/target/x86_64_unknown_bitrig.rs
@@ -8,14 +8,14 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::bitrig_base::opts();
     base.max_atomic_width = 64;
     base.pre_link_args.push("-m64".to_string());
 
-    Target {
+    Ok(Target {
         llvm_target: "x86_64-unknown-bitrig".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),
@@ -25,5 +25,5 @@ pub fn target() -> Target {
         target_env: "".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/x86_64_unknown_dragonfly.rs b/src/librustc_back/target/x86_64_unknown_dragonfly.rs
index 2535071f308..7e40d49b870 100644
--- a/src/librustc_back/target/x86_64_unknown_dragonfly.rs
+++ b/src/librustc_back/target/x86_64_unknown_dragonfly.rs
@@ -8,15 +8,15 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::dragonfly_base::opts();
     base.cpu = "x86-64".to_string();
     base.max_atomic_width = 64;
     base.pre_link_args.push("-m64".to_string());
 
-    Target {
+    Ok(Target {
         llvm_target: "x86_64-unknown-dragonfly".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),
@@ -26,5 +26,5 @@ pub fn target() -> Target {
         target_env: "".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/x86_64_unknown_freebsd.rs b/src/librustc_back/target/x86_64_unknown_freebsd.rs
index d3ad0578aeb..f38cdd4bec5 100644
--- a/src/librustc_back/target/x86_64_unknown_freebsd.rs
+++ b/src/librustc_back/target/x86_64_unknown_freebsd.rs
@@ -8,15 +8,15 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::freebsd_base::opts();
     base.cpu = "x86-64".to_string();
     base.max_atomic_width = 64;
     base.pre_link_args.push("-m64".to_string());
 
-    Target {
+    Ok(Target {
         llvm_target: "x86_64-unknown-freebsd".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),
@@ -26,5 +26,5 @@ pub fn target() -> Target {
         target_env: "".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/x86_64_unknown_linux_gnu.rs b/src/librustc_back/target/x86_64_unknown_linux_gnu.rs
index 7908e0d581b..ef81d397a8f 100644
--- a/src/librustc_back/target/x86_64_unknown_linux_gnu.rs
+++ b/src/librustc_back/target/x86_64_unknown_linux_gnu.rs
@@ -8,15 +8,15 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::linux_base::opts();
     base.cpu = "x86-64".to_string();
     base.max_atomic_width = 64;
     base.pre_link_args.push("-m64".to_string());
 
-    Target {
+    Ok(Target {
         llvm_target: "x86_64-unknown-linux-gnu".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),
@@ -26,5 +26,5 @@ pub fn target() -> Target {
         target_env: "gnu".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/x86_64_unknown_linux_musl.rs b/src/librustc_back/target/x86_64_unknown_linux_musl.rs
index 3301e0e0dc9..4bad7754b39 100644
--- a/src/librustc_back/target/x86_64_unknown_linux_musl.rs
+++ b/src/librustc_back/target/x86_64_unknown_linux_musl.rs
@@ -8,15 +8,15 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::linux_musl_base::opts();
     base.cpu = "x86-64".to_string();
     base.max_atomic_width = 64;
     base.pre_link_args.push("-m64".to_string());
 
-    Target {
+    Ok(Target {
         llvm_target: "x86_64-unknown-linux-musl".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),
@@ -26,5 +26,5 @@ pub fn target() -> Target {
         target_env: "musl".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/x86_64_unknown_netbsd.rs b/src/librustc_back/target/x86_64_unknown_netbsd.rs
index 7e6d1b78469..5145e52d6b4 100644
--- a/src/librustc_back/target/x86_64_unknown_netbsd.rs
+++ b/src/librustc_back/target/x86_64_unknown_netbsd.rs
@@ -8,14 +8,14 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::netbsd_base::opts();
     base.max_atomic_width = 64;
     base.pre_link_args.push("-m64".to_string());
 
-    Target {
+    Ok(Target {
         llvm_target: "x86_64-unknown-netbsd".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),
@@ -25,5 +25,5 @@ pub fn target() -> Target {
         target_env: "".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/x86_64_unknown_openbsd.rs b/src/librustc_back/target/x86_64_unknown_openbsd.rs
index 823b0994b0a..339dbd591a0 100644
--- a/src/librustc_back/target/x86_64_unknown_openbsd.rs
+++ b/src/librustc_back/target/x86_64_unknown_openbsd.rs
@@ -8,15 +8,15 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::openbsd_base::opts();
     base.cpu = "x86-64".to_string();
     base.max_atomic_width = 64;
     base.pre_link_args.push("-m64".to_string());
 
-    Target {
+    Ok(Target {
         llvm_target: "x86_64-unknown-openbsd".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),
@@ -26,5 +26,5 @@ pub fn target() -> Target {
         target_env: "".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }