Add explanations to tests

Author: canndrew

src/test/compile-fail/call-fn-never-arg-wrong-type.rs

@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// Test that we can't pass other types for !
+
 #![feature(never_type)]
 
 fn foo(x: !) -> ! {

src/test/compile-fail/never-assign-dead-code.rs

@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// Test that an assignment of type ! makes the rest of the block dead code.
+
 #![feature(never_type)]
 #![deny(unused, unreachable_code)]
 

src/test/compile-fail/never-assign-wrong-type.rs

@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// Test that we can't use another type in place of !
+
 #![feature(never_type)]
 
 fn main() {

src/test/compile-fail/never-disabled.rs

@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// Test that ! errors when used in illegal positions with feature(never_type) disabled
+
 trait Foo {
     type Wub;
 }

src/test/compile-fail/never-fallback.rs

@@ -8,6 +8,9 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// Test that diverging types default to ! when feature(never_type) is enabled. This test is the
+// same as run-pass/unit-fallback.rs except that ! is enabled.
+
 #![feature(never_type)]
 
 trait Balls: Sized {

src/test/compile-fail/return-from-diverging.rs

@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// Test that return another type in place of ! raises a type mismatch.
+
 fn fail() -> ! {
     return "wow"; //~ ERROR mismatched types
 }

src/test/compile-fail/return-unit-from-diverging.rs

@@ -8,6 +8,9 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// Test that we get the usual error that we'd get for any other return type and not something about
+// diverging functions not being able to return.
+
 fn fail() -> ! {
     return; //~ ERROR in a function whose return type is not
 }

src/test/run-fail/adjust_never.rs

@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// Test that a variable of type ! can coerce to another type.
+
 #![feature(never_type)]
 
 // error-pattern:explicit

src/test/run-fail/call-fn-never-arg.rs

@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// Test that we can use a ! for an argument of type !
+
 // error-pattern:wowzers!
 
 #![feature(never_type)]

src/test/run-fail/cast-never.rs

@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// Test that we can explicitly cast ! to another type
+
 #![feature(never_type)]
 
 // error-pattern:explicit

src/test/run-fail/never-associated-type.rs

@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// Test that we can use ! as an associated type.
+
 #![feature(never_type)]
 
 // error-pattern:kapow!

src/test/run-fail/never-type-arg.rs

@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// Test that we can use ! as an argument to a trait impl.
+
 // error-pattern:oh no!
 
 #![feature(never_type)]

src/test/run-fail/return-never-coerce.rs

@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// Test that ! coerces to other types.
+
 // error-pattern:aah!
 
 fn call_another_fn<T, F: FnOnce() -> T>(f: F) -> T {

src/test/run-pass/impl-for-never.rs

@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// Test that we can call static methods on ! both directly and when it appears in a generic
+
 #![feature(never_type)]
 
 trait StringifyType {

src/test/run-pass/never-result.rs

@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// Test that we can extract a ! through pattern matching then use it as several different types.
+
 #![feature(never_type)]
 
 fn main() {

src/test/run-pass/never_coercions.rs

@@ -8,6 +8,9 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// Test that having something of type ! doesn't screw up type-checking and that it coerces to the
+// LUB type of the other match arms.
+
 fn main() {
     let v: Vec<u32> = Vec::new();
     match 0u32 {

src/test/run-pass/unit-fallback.rs

@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// Test that diverging types default to () (with feature(never_type) disabled).
+
 trait Balls: Sized {
     fn smeg() -> Result<Self, ()>;
 }