diff --git a/lib/environ/src/lib.rs b/lib/environ/src/lib.rs
index bd7d17c836..8a16bf0fa0 100644
--- a/lib/environ/src/lib.rs
+++ b/lib/environ/src/lib.rs
@@ -9,7 +9,7 @@
 #![cfg_attr(feature = "clippy", plugin(clippy(conf_file = "../../clippy.toml")))]
 #![cfg_attr(
     feature = "cargo-clippy",
-    allow(new_without_default, new_without_default_derive)
+    allow(clippy::new_without_default, clippy::new_without_default_derive)
 )]
 #![cfg_attr(
     feature = "cargo-clippy",
diff --git a/lib/execute/src/lib.rs b/lib/execute/src/lib.rs
index 394aa02358..18bf5ff3b5 100644
--- a/lib/execute/src/lib.rs
+++ b/lib/execute/src/lib.rs
@@ -6,7 +6,7 @@
 #![cfg_attr(feature = "clippy", plugin(clippy(conf_file = "../../clippy.toml")))]
 #![cfg_attr(
     feature = "cargo-clippy",
-    allow(new_without_default, new_without_default_derive)
+    allow(clippy::new_without_default, clippy::new_without_default_derive)
 )]
 #![cfg_attr(
     feature = "cargo-clippy",
diff --git a/lib/execute/src/vmcontext.rs b/lib/execute/src/vmcontext.rs
index ec985af9b5..ebe520d792 100644
--- a/lib/execute/src/vmcontext.rs
+++ b/lib/execute/src/vmcontext.rs
@@ -174,32 +174,32 @@ mod test_vmglobal_definition {
 }
 
 impl VMGlobalDefinition {
-    #[allow(cast_ptr_alignment)]
+    #[allow(clippy::cast_ptr_alignment)]
     pub unsafe fn as_i32(&mut self) -> &mut i32 {
         &mut *(self.storage.as_mut().as_mut_ptr() as *mut u8 as *mut i32)
     }
 
-    #[allow(cast_ptr_alignment)]
+    #[allow(clippy::cast_ptr_alignment)]
     pub unsafe fn as_i64(&mut self) -> &mut i64 {
         &mut *(self.storage.as_mut().as_mut_ptr() as *mut u8 as *mut i64)
     }
 
-    #[allow(cast_ptr_alignment)]
+    #[allow(clippy::cast_ptr_alignment)]
     pub unsafe fn as_f32(&mut self) -> &mut f32 {
         &mut *(self.storage.as_mut().as_mut_ptr() as *mut u8 as *mut f32)
     }
 
-    #[allow(cast_ptr_alignment)]
+    #[allow(clippy::cast_ptr_alignment)]
     pub unsafe fn as_f32_bits(&mut self) -> &mut u32 {
         &mut *(self.storage.as_mut().as_mut_ptr() as *mut u8 as *mut u32)
     }
 
-    #[allow(cast_ptr_alignment)]
+    #[allow(clippy::cast_ptr_alignment)]
     pub unsafe fn as_f64(&mut self) -> &mut f64 {
         &mut *(self.storage.as_mut().as_mut_ptr() as *mut u8 as *mut f64)
     }
 
-    #[allow(cast_ptr_alignment)]
+    #[allow(clippy::cast_ptr_alignment)]
     pub unsafe fn as_f64_bits(&mut self) -> &mut u64 {
         &mut *(self.storage.as_mut().as_mut_ptr() as *mut u8 as *mut u64)
     }
@@ -578,7 +578,7 @@ impl VMContext {
     }
 
     /// Return a mutable reference to the associated `Instance`.
-    #[allow(cast_ptr_alignment)]
+    #[allow(clippy::cast_ptr_alignment)]
     pub unsafe fn instance(&mut self) -> &mut Instance {
         &mut *((self as *mut Self as *mut u8).offset(-Instance::vmctx_offset()) as *mut Instance)
     }
diff --git a/lib/obj/src/lib.rs b/lib/obj/src/lib.rs
index e06fb7a73a..012bf1cb00 100644
--- a/lib/obj/src/lib.rs
+++ b/lib/obj/src/lib.rs
@@ -10,7 +10,7 @@
 #![cfg_attr(feature = "clippy", plugin(clippy(conf_file = "../../clippy.toml")))]
 #![cfg_attr(
     feature = "cargo-clippy",
-    allow(new_without_default, new_without_default_derive)
+    allow(clippy::new_without_default, clippy::new_without_default_derive)
 )]
 #![cfg_attr(
     feature = "cargo-clippy",
diff --git a/lib/wast/src/lib.rs b/lib/wast/src/lib.rs
index ca4d3d3c3a..1f8fc8f832 100644
--- a/lib/wast/src/lib.rs
+++ b/lib/wast/src/lib.rs
@@ -6,7 +6,7 @@
 #![cfg_attr(feature = "clippy", plugin(clippy(conf_file = "../../clippy.toml")))]
 #![cfg_attr(
     feature = "cargo-clippy",
-    allow(new_without_default, new_without_default_derive)
+    allow(clippy::new_without_default, clippy::new_without_default_derive)
 )]
 #![cfg_attr(
     feature = "cargo-clippy",
diff --git a/lib/wast/src/spectest.rs b/lib/wast/src/spectest.rs
index 92d905fd74..dafec15b3b 100644
--- a/lib/wast/src/spectest.rs
+++ b/lib/wast/src/spectest.rs
@@ -6,29 +6,36 @@ use target_lexicon::HOST;
 use wasmtime_environ::{translate_signature, MemoryPlan, MemoryStyle, TablePlan, TableStyle};
 use wasmtime_execute::{ExportValue, Resolver, VMGlobal, VMMemory, VMTable};
 
+#[allow(clippy::print_stdout)]
 extern "C" fn spectest_print() {}
 
+#[allow(clippy::print_stdout)]
 extern "C" fn spectest_print_i32(x: i32) {
     println!("{}: i32", x);
 }
 
+#[allow(clippy::print_stdout)]
 extern "C" fn spectest_print_i64(x: i64) {
     println!("{}: i64", x);
 }
 
+#[allow(clippy::print_stdout)]
 extern "C" fn spectest_print_f32(x: f32) {
     println!("{}: f32", x);
 }
 
+#[allow(clippy::print_stdout)]
 extern "C" fn spectest_print_f64(x: f64) {
     println!("{}: f64", x);
 }
 
+#[allow(clippy::print_stdout)]
 extern "C" fn spectest_print_i32_f32(x: i32, y: f32) {
     println!("{}: i32", x);
     println!("{}: f32", y);
 }
 
+#[allow(clippy::print_stdout)]
 extern "C" fn spectest_print_f64_f64(x: f64, y: f64) {
     println!("{}: f64", x);
     println!("{}: f64", y);
diff --git a/lib/wast/src/wast.rs b/lib/wast/src/wast.rs
index 067d0fc686..f77711e872 100644
--- a/lib/wast/src/wast.rs
+++ b/lib/wast/src/wast.rs
@@ -44,7 +44,11 @@ impl Instances {
         self.namespace.insert(name, world);
     }
 
-    pub fn perform_action(&mut self, isa: &isa::TargetIsa, action: Action) -> ActionOutcome {
+    pub fn perform_action(
+        &mut self,
+        isa: &isa::TargetIsa,
+        action: Action,
+    ) -> Result<ActionOutcome, String> {
         match action {
             Action::Invoke {
                 module,
@@ -62,44 +66,50 @@ impl Instances {
                 }
                 match module {
                     None => match self.current {
-                        None => panic!("invoke performed with no module present"),
+                        None => Err("invoke performed with no module present".to_string()),
                         Some(ref mut instance_world) => instance_world
                             .invoke(&mut self.code, isa, &field, &value_args)
-                            .expect(&format!("error invoking {} in current module", field)),
+                            .map_err(|e| {
+                                format!("error invoking {} in current module: {}", field, e)
+                            }),
                     },
                     Some(name) => self
                         .namespace
                         .get_mut(&name)
-                        .expect(&format!("module {} not declared", name))
+                        .ok_or_else(|| format!("module {} not declared", name))?
                         .invoke(&mut self.code, isa, &field, &value_args)
-                        .expect(&format!("error invoking {} in module {}", field, name)),
+                        .map_err(|e| format!("error invoking {} in module {}: {}", field, name, e)),
                 }
             }
             Action::Get { module, field } => {
                 let value = match module {
                     None => match self.current {
-                        None => panic!("get performed with no module present"),
-                        Some(ref mut instance_world) => instance_world
-                            .get(&field)
-                            .expect(&format!("error getting {} in current module", field)),
+                        None => return Err("get performed with no module present".to_string()),
+                        Some(ref mut instance_world) => {
+                            instance_world.get(&field).map_err(|e| {
+                                format!("error getting {} in current module: {}", field, e)
+                            })?
+                        }
                     },
                     Some(name) => self
                         .namespace
                         .get_mut(&name)
-                        .expect(&format!("module {} not declared", name))
+                        .ok_or_else(|| format!("module {} not declared", name))?
                         .get(&field)
-                        .expect(&format!("error getting {} in module {}", field, name)),
+                        .map_err(|e| {
+                            format!("error getting {} in module {}: {}", field, name, e)
+                        })?,
                 };
-                ActionOutcome::Returned {
+                Ok(ActionOutcome::Returned {
                     values: vec![value],
-                }
+                })
             }
         }
     }
 }
 
 /// Run a wast script from a byte buffer.
-pub fn wast_buffer(name: &str, isa: &isa::TargetIsa, wast: &[u8]) {
+pub fn wast_buffer(name: &str, isa: &isa::TargetIsa, wast: &[u8]) -> Result<(), String> {
     let mut parser = ScriptParser::from_str(str::from_utf8(wast).unwrap()).unwrap();
     let mut instances = Instances::new();
 
@@ -107,19 +117,19 @@ pub fn wast_buffer(name: &str, isa: &isa::TargetIsa, wast: &[u8]) {
         match kind {
             CommandKind::Module { module, name } => {
                 if let Some(name) = name {
-                    instances.define_named_module(&*isa, name, module.clone());
+                    instances.define_named_module(isa, name, module.clone());
                 }
 
-                instances.define_unnamed_module(&*isa, module)
+                instances.define_unnamed_module(isa, module)
             }
-            CommandKind::PerformAction(action) => match instances.perform_action(&*isa, action) {
+            CommandKind::PerformAction(action) => match instances.perform_action(isa, action)? {
                 ActionOutcome::Returned { .. } => {}
                 ActionOutcome::Trapped { message } => {
                     panic!("{}:{}: a trap occurred: {}", name, line, message);
                 }
             },
             CommandKind::AssertReturn { action, expected } => {
-                match instances.perform_action(&*isa, action) {
+                match instances.perform_action(isa, action)? {
                     ActionOutcome::Returned { values } => {
                         for (v, e) in values.iter().zip(expected.iter()) {
                             match *e {
@@ -147,7 +157,7 @@ pub fn wast_buffer(name: &str, isa: &isa::TargetIsa, wast: &[u8]) {
                 }
             }
             CommandKind::AssertTrap { action, message } => {
-                match instances.perform_action(&*isa, action) {
+                match instances.perform_action(isa, action)? {
                     ActionOutcome::Returned { values } => panic!(
                         "{}:{}: expected trap, but invoke returned with {:?}",
                         name, line, values
@@ -163,7 +173,7 @@ pub fn wast_buffer(name: &str, isa: &isa::TargetIsa, wast: &[u8]) {
                 }
             }
             CommandKind::AssertExhaustion { action } => {
-                match instances.perform_action(&*isa, action) {
+                match instances.perform_action(isa, action)? {
                     ActionOutcome::Returned { values } => panic!(
                         "{}:{}: expected exhaustion, but invoke returned with {:?}",
                         name, line, values
@@ -177,7 +187,7 @@ pub fn wast_buffer(name: &str, isa: &isa::TargetIsa, wast: &[u8]) {
                 }
             }
             CommandKind::AssertReturnCanonicalNan { action } => {
-                match instances.perform_action(&*isa, action) {
+                match instances.perform_action(isa, action)? {
                     ActionOutcome::Returned { values } => {
                         for v in values.iter() {
                             match v {
@@ -210,7 +220,7 @@ pub fn wast_buffer(name: &str, isa: &isa::TargetIsa, wast: &[u8]) {
                 }
             }
             CommandKind::AssertReturnArithmeticNan { action } => {
-                match instances.perform_action(&*isa, action) {
+                match instances.perform_action(isa, action)? {
                     ActionOutcome::Returned { values } => {
                         for v in values.iter() {
                             match v {
@@ -247,13 +257,14 @@ pub fn wast_buffer(name: &str, isa: &isa::TargetIsa, wast: &[u8]) {
             }
         }
     }
+
+    Ok(())
 }
 
 /// Run a wast script from a file.
 pub fn wast_file(path: &Path, isa: &isa::TargetIsa) -> Result<(), String> {
     let wast = read_to_end(path).map_err(|e| e.to_string())?;
-    wast_buffer(&path.display().to_string(), isa, &wast);
-    Ok(())
+    wast_buffer(&path.display().to_string(), isa, &wast)
 }
 
 fn read_to_end(path: &Path) -> Result<Vec<u8>, io::Error> {
diff --git a/src/run_wast.rs b/src/run_wast.rs
index 63520186b9..df4a971b0d 100644
--- a/src/run_wast.rs
+++ b/src/run_wast.rs
@@ -10,7 +10,7 @@
 #![cfg_attr(feature = "clippy", plugin(clippy(conf_file = "../../clippy.toml")))]
 #![cfg_attr(
     feature = "cargo-clippy",
-    allow(new_without_default, new_without_default_derive)
+    allow(clippy::new_without_default, clippy::new_without_default_derive)
 )]
 #![cfg_attr(
     feature = "cargo-clippy",
@@ -96,6 +96,7 @@ fn main() {
     let isa = isa_builder.finish(settings::Flags::new(flag_builder));
     for filename in &args.arg_file {
         let path = Path::new(&filename);
-        wast_file(path, &*isa).expect(&format!("error reading file {}", path.display()));
+        wast_file(path, &*isa)
+            .unwrap_or_else(|e| panic!("error reading file {}: {}", path.display(), e));
     }
 }
diff --git a/src/wasm2obj.rs b/src/wasm2obj.rs
index dab26c404a..70b6b15d1a 100644
--- a/src/wasm2obj.rs
+++ b/src/wasm2obj.rs
@@ -14,7 +14,7 @@
 #![cfg_attr(feature = "clippy", plugin(clippy(conf_file = "../../clippy.toml")))]
 #![cfg_attr(
     feature = "cargo-clippy",
-    allow(new_without_default, new_without_default_derive)
+    allow(clippy::new_without_default, clippy::new_without_default_derive)
 )]
 #![cfg_attr(
     feature = "cargo-clippy",
diff --git a/src/wasmtime.rs b/src/wasmtime.rs
index b1c6d4ce1e..4c23f0a06f 100644
--- a/src/wasmtime.rs
+++ b/src/wasmtime.rs
@@ -15,7 +15,7 @@
 #![cfg_attr(feature = "clippy", plugin(clippy(conf_file = "../../clippy.toml")))]
 #![cfg_attr(
     feature = "cargo-clippy",
-    allow(new_without_default, new_without_default_derive)
+    allow(clippy::new_without_default, clippy::new_without_default_derive)
 )]
 #![cfg_attr(
     feature = "cargo-clippy",
@@ -128,7 +128,7 @@ fn main() {
     let isa = isa_builder.finish(settings::Flags::new(flag_builder));
     for filename in &args.arg_file {
         let path = Path::new(&filename);
-        match handle_module(&args, path.to_path_buf(), &*isa) {
+        match handle_module(&args, path, &*isa) {
             Ok(()) => {}
             Err(message) => {
                 let name = path.as_os_str().to_string_lossy();
@@ -139,8 +139,9 @@ fn main() {
     }
 }
 
-fn handle_module(args: &Args, path: PathBuf, isa: &TargetIsa) -> Result<(), String> {
-    let mut data = read_to_end(path.clone()).map_err(|err| String::from(err.description()))?;
+fn handle_module(args: &Args, path: &Path, isa: &TargetIsa) -> Result<(), String> {
+    let mut data =
+        read_to_end(path.to_path_buf()).map_err(|err| String::from(err.description()))?;
     // if data is using wat-format, first convert data to wasm
     if !data.starts_with(&[b'\0', b'a', b's', b'm']) {
         data = wabt::wat2wasm(data).map_err(|err| String::from(err.description()))?;