3 files changed, 38 insertions, 6 deletions
diff --git a/src/librustc_error_codes/error_codes/E0124.md b/src/librustc_error_codes/error_codes/E0124.md
index a7836526a7d..8af7cb819cf 100644
--- a/src/librustc_error_codes/error_codes/E0124.md
+++ b/src/librustc_error_codes/error_codes/E0124.md
@@ -1,5 +1,6 @@
-You declared two fields of a struct with the same name. Erroneous code
-example:
+A struct was declared with two fields having the same name.
+
+Erroneous code example:
 
 ```compile_fail,E0124
 struct Foo {
diff --git a/src/librustc_error_codes/error_codes/E0128.md b/src/librustc_error_codes/error_codes/E0128.md
index d0a4b32f968..6f8dfe3a73b 100644
--- a/src/librustc_error_codes/error_codes/E0128.md
+++ b/src/librustc_error_codes/error_codes/E0128.md
@@ -1,4 +1,5 @@
-Type parameter defaults can only use parameters that occur before them.
+A type parameter with default value is using forward declared identifier.
+
 Erroneous code example:
 
 ```compile_fail,E0128
@@ -7,11 +8,11 @@ struct Foo<T = U, U = ()> {
     field2: U,
 }
 // error: type parameters with a default cannot use forward declared
-// identifiers
+//        identifiers
 ```
 
-Since type parameters are evaluated in-order, you may be able to fix this issue
-by doing:
+Type parameter defaults can only use parameters that occur before them. Since
+type parameters are evaluated in-order, this issue could be fixed by doing:
 
 ```
 struct Foo<U = (), T = U> {
diff --git a/src/librustc_error_codes/error_codes/E0627.md b/src/librustc_error_codes/error_codes/E0627.md
new file mode 100644
index 00000000000..21358e1e567
--- /dev/null
+++ b/src/librustc_error_codes/error_codes/E0627.md
@@ -0,0 +1,30 @@
+A yield expression was used outside of the generator literal.
+
+Erroneous code example:
+
+```compile_fail,E0627
+#![feature(generators, generator_trait)]
+
+fn fake_generator() -> &'static str {
+    yield 1;
+    return "foo"
+}
+
+fn main() {
+    let mut generator = fake_generator;
+}
+```
+
+The error occurs because keyword `yield` can only be used inside the generator
+literal. This can be fixed by constructing the generator correctly.
+
+```
+#![feature(generators, generator_trait)]
+
+fn main() {
+    let mut generator = || {
+        yield 1;
+        return "foo"
+    };
+}
+```