Ctd. #18087: complete :since: info for all warnings in users guide

Some warnings have been there "forever" and I could not trace back the
exact genesis, so I wrote "since at least 5.04".

The flag `helpful-errors` could have been added in 7.2 already.  I
wrote 7.4 since I have no 7.2 available and it is not recognized by 7.0.

4 files changed, 39 insertions, 2 deletions

diff --git a/compiler/GHC/Driver/Flags.hs b/compiler/GHC/Driver/Flags.hs
index fa9c79b41d..ce68014d2d 100644
--- a/compiler/GHC/Driver/Flags.hs
+++ b/compiler/GHC/Driver/Flags.hs
@@ -278,8 +278,8 @@ data GeneralFlag
    | Opt_LocalGhciHistory
    | Opt_NoIt
    | Opt_HelpfulErrors
-   | Opt_DeferTypeErrors
-   | Opt_DeferTypedHoles
+   | Opt_DeferTypeErrors             -- Since 7.6
+   | Opt_DeferTypedHoles             -- Since 7.10
    | Opt_DeferOutOfScopeVariables
    | Opt_PIC                         -- ^ @-fPIC@
    | Opt_PIE                         -- ^ @-fPIE@
diff --git a/compiler/GHC/Driver/Session.hs b/compiler/GHC/Driver/Session.hs
index 6fc71e878a..02b1a637ff 100644
--- a/compiler/GHC/Driver/Session.hs
+++ b/compiler/GHC/Driver/Session.hs
@@ -291,6 +291,7 @@ import qualified GHC.LanguageExtensions as LangExt
 -- If you modify anything in this file please make sure that your changes are
 -- described in the User's Guide. Please update the flag description in the
 -- users guide (docs/users_guide) whenever you add or change a flag.
+-- Please make sure you add ":since:" information to new flags.
 
 -- Note [Supporting CLI completion]
 -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
diff --git a/docs/users_guide/exts/defer_type_errors.rst b/docs/users_guide/exts/defer_type_errors.rst
index 8d502d3708..a2647fc9ef 100644
--- a/docs/users_guide/exts/defer_type_errors.rst
+++ b/docs/users_guide/exts/defer_type_errors.rst
@@ -3,6 +3,8 @@
 Deferring type errors to runtime
 ================================
 
+Since GHC 7.6.1.
+
 While developing, sometimes it is desirable to allow compilation to
 succeed even if there are type errors in the code. Consider the
 following case: ::
diff --git a/docs/users_guide/using-warnings.rst b/docs/users_guide/using-warnings.rst
index 3da70bf3f2..7f72b3eb20 100644
--- a/docs/users_guide/using-warnings.rst
+++ b/docs/users_guide/using-warnings.rst
@@ -292,6 +292,8 @@ of ``-W(no-)*``.
     :reverse: -Wno-prepositive-qualified-module
     :category:
 
+    :since: 8.10
+
     Normally, imports are qualified prepositively: ``import qualified M``.
     By using :extension:`ImportQualifiedPost`, the qualified keyword can be used after the module name.
     Like so: ``import M qualified``. This will warn when the first, prepositive syntax is used.
@@ -337,6 +339,8 @@ of ``-W(no-)*``.
     :reverse: -fno-defer-type-errors
     :category:
 
+    :since: 7.6
+
     :implies: :ghc-flag:`-fdefer-typed-holes`, :ghc-flag:`-fdefer-out-of-scope-variables`
 
     Defer as many type errors as possible until runtime. At compile time
@@ -354,6 +358,8 @@ of ``-W(no-)*``.
     :reverse: -fno-defer-typed-holes
     :category:
 
+    :since: 7.10
+
     Defer typed holes errors (errors about names with a leading underscore
     (e.g., “_”, “_foo”, “_bar”)) until runtime. This will turn the errors
     produced by :ref:`typed holes <typed-holes>` into warnings. Using a value
@@ -389,6 +395,8 @@ of ``-W(no-)*``.
     :reverse: -Wno-deferred-out-of-scope-variables
     :category:
 
+    :since: 8.0
+
     Warn when a deferred out-of-scope variable is encountered.
 
 .. ghc-flag:: -Wpartial-type-signatures
@@ -416,6 +424,8 @@ of ``-W(no-)*``.
     :reverse: -fno-helpful-errors
     :category:
 
+    :since: 7.4
+
     :default: on
 
     When a name or package is not found in scope, make suggestions for
@@ -835,6 +845,8 @@ of ``-W(no-)*``.
     :reverse: -Wno-duplicate-exports
     :category:
 
+    :since: at least 5.04
+
     :default: on
 
     .. index::
@@ -853,6 +865,8 @@ of ``-W(no-)*``.
     :reverse: -Wno-hi-shadowing
     :category:
 
+    :since: at least 5.04, deprecated
+
     .. index::
        single: shadowing; interface files
 
@@ -995,6 +1009,8 @@ of ``-W(no-)*``.
     :type: dynamic
     :category:
 
+    :since: 8.10
+
     :default: 30
 
     The pattern match checker works by assigning symbolic values to each
@@ -1064,6 +1080,8 @@ of ``-W(no-)*``.
     :reverse: -Wno-missing-fields
     :category:
 
+    :since: at least 5.04
+
     .. index::
        single: missing fields, warning
        single: fields, missing
@@ -1134,6 +1152,8 @@ of ``-W(no-)*``.
     :reverse: -Wno-missing-methods
     :category:
 
+    :since: at least 5.04
+
     :default: on
 
     .. index::
@@ -1154,6 +1174,8 @@ of ``-W(no-)*``.
     :reverse: -Wno-missing-signatures
     :category:
 
+    :since: at least 5.04
+
     :default: off
 
     .. index::
@@ -1304,6 +1326,8 @@ of ``-W(no-)*``.
     :reverse: -Wno-name-shadowing
     :category:
 
+    :since: at least 5.04
+
     .. index::
        single: shadowing, warning
 
@@ -1354,6 +1378,8 @@ of ``-W(no-)*``.
     :reverse: -Wno-overlapping-patterns
     :category:
 
+    :since: at least 5.04
+
     .. index::
        single: overlapping patterns, warning
        single: patterns, overlapping
@@ -1534,6 +1560,8 @@ of ``-W(no-)*``.
     :reverse: -Wno-type-defaults
     :category:
 
+    :since: at least 5.04
+
     :default: off
 
     .. index::
@@ -1624,6 +1652,8 @@ of ``-W(no-)*``.
     :reverse: -Wno-unused-binds
     :category:
 
+    :since: at least 5.04
+
     .. index::
        single: unused binds, warning
        single: binds, unused
@@ -1723,6 +1753,8 @@ of ``-W(no-)*``.
     :reverse: -Wno-unused-imports
     :category:
 
+    :since: at least 5.04
+
     .. index::
        single: unused imports, warning
        single: imports, unused
@@ -1738,6 +1770,8 @@ of ``-W(no-)*``.
     :reverse: -Wno-unused-matches
     :category:
 
+    :since: at least 5.04
+
     .. index::
        single: unused matches, warning
        single: matches, unused