Use &'static str rather than Cow<str> for pass names.

lib/filetests/src/subtest.rs

@@ -45,7 +45,7 @@ impl<'a> Context<'a> {
 /// trait object.
 pub trait SubTest {
     /// Name identifying this subtest. Typically the same as the test command.
-    fn name(&self) -> Cow<str>;
+    fn name(&self) -> &'static str;
 
     /// Should the verifier be run on the function before running the test?
     fn needs_verifier(&self) -> bool {

lib/filetests/src/test_binemit.rs

@@ -96,8 +96,8 @@ impl binemit::CodeSink for TextSink {
 }
 
 impl SubTest for TestBinEmit {
-    fn name(&self) -> Cow<str> {
+    fn name(&self) -> &'static str {
-        Cow::from("binemit")
+        "binemit"
     }
 
     fn is_mutating(&self) -> bool {

lib/filetests/src/test_cat.rs

@@ -23,8 +23,8 @@ pub fn subtest(parsed: &TestCommand) -> STResult<Box<SubTest>> {
 }
 
 impl SubTest for TestCat {
-    fn name(&self) -> Cow<str> {
+    fn name(&self) -> &'static str {
-        Cow::from("cat")
+        "cat"
     }
 
     fn needs_verifier(&self) -> bool {

lib/filetests/src/test_compile.rs

@@ -22,8 +22,8 @@ pub fn subtest(parsed: &TestCommand) -> Result<Box<SubTest>> {
 }
 
 impl SubTest for TestCompile {
-    fn name(&self) -> Cow<str> {
+    fn name(&self) -> &'static str {
-        Cow::from("compile")
+        "compile"
     }
 
     fn is_mutating(&self) -> bool {

lib/filetests/src/test_dce.rs

@@ -25,8 +25,8 @@ pub fn subtest(parsed: &TestCommand) -> Result<Box<SubTest>> {
 }
 
 impl SubTest for TestDCE {
-    fn name(&self) -> Cow<str> {
+    fn name(&self) -> &'static str {
-        Cow::from("dce")
+        "dce"
     }
 
     fn is_mutating(&self) -> bool {

lib/filetests/src/test_domtree.rs

@@ -36,8 +36,8 @@ pub fn subtest(parsed: &TestCommand) -> Result<Box<SubTest>> {
 }
 
 impl SubTest for TestDomtree {
-    fn name(&self) -> Cow<str> {
+    fn name(&self) -> &'static str {
-        Cow::from("domtree")
+        "domtree"
     }
 
     // Extract our own dominator tree from

lib/filetests/src/test_legalizer.rs

@@ -23,8 +23,8 @@ pub fn subtest(parsed: &TestCommand) -> Result<Box<SubTest>> {
 }
 
 impl SubTest for TestLegalizer {
-    fn name(&self) -> Cow<str> {
+    fn name(&self) -> &'static str {
-        Cow::from("legalizer")
+        "legalizer"
     }
 
     fn is_mutating(&self) -> bool {

lib/filetests/src/test_licm.rs

@@ -25,8 +25,8 @@ pub fn subtest(parsed: &TestCommand) -> Result<Box<SubTest>> {
 }
 
 impl SubTest for TestLICM {
-    fn name(&self) -> Cow<str> {
+    fn name(&self) -> &'static str {
-        Cow::from("licm")
+        "licm"
     }
 
     fn is_mutating(&self) -> bool {

lib/filetests/src/test_postopt.rs

@@ -22,8 +22,8 @@ pub fn subtest(parsed: &TestCommand) -> Result<Box<SubTest>> {
 }
 
 impl SubTest for TestPostopt {
-    fn name(&self) -> Cow<str> {
+    fn name(&self) -> &'static str {
-        Cow::from("postopt")
+        "postopt"
     }
 
     fn is_mutating(&self) -> bool {

lib/filetests/src/test_preopt.rs

@@ -22,8 +22,8 @@ pub fn subtest(parsed: &TestCommand) -> Result<Box<SubTest>> {
 }
 
 impl SubTest for TestPreopt {
-    fn name(&self) -> Cow<str> {
+    fn name(&self) -> &'static str {
-        Cow::from("preopt")
+        "preopt"
     }
 
     fn is_mutating(&self) -> bool {

lib/filetests/src/test_print_cfg.rs

@@ -23,8 +23,8 @@ pub fn subtest(parsed: &TestCommand) -> STResult<Box<SubTest>> {
 }
 
 impl SubTest for TestPrintCfg {
-    fn name(&self) -> Cow<str> {
+    fn name(&self) -> &'static str {
-        Cow::from("print-cfg")
+        "print-cfg"
     }
 
     fn needs_verifier(&self) -> bool {

lib/filetests/src/test_regalloc.rs

@@ -25,8 +25,8 @@ pub fn subtest(parsed: &TestCommand) -> Result<Box<SubTest>> {
 }
 
 impl SubTest for TestRegalloc {
-    fn name(&self) -> Cow<str> {
+    fn name(&self) -> &'static str {
-        Cow::from("regalloc")
+        "regalloc"
     }
 
     fn is_mutating(&self) -> bool {

lib/filetests/src/test_simple_gvn.rs

@@ -25,8 +25,8 @@ pub fn subtest(parsed: &TestCommand) -> Result<Box<SubTest>> {
 }
 
 impl SubTest for TestSimpleGVN {
-    fn name(&self) -> Cow<str> {
+    fn name(&self) -> &'static str {
-        Cow::from("simple-gvn")
+        "simple-gvn"
     }
 
     fn is_mutating(&self) -> bool {

lib/filetests/src/test_verifier.rs

@@ -28,8 +28,8 @@ pub fn subtest(parsed: &TestCommand) -> Result<Box<SubTest>> {
 }
 
 impl SubTest for TestVerifier {
-    fn name(&self) -> Cow<str> {
+    fn name(&self) -> &'static str {
-        Cow::from("verifier")
+        "verifier"
     }
 
     fn needs_verifier(&self) -> bool {