Fix #23241 - duplicate deprecation message for enum member accessed by name

A deprecated enum member accessed by its unqualified name (an anonymous
enum member, a member found via `with`, or an ImportC enumerator) reported
the deprecation twice: once during name resolution and again in getVarExp(),
which already performs the deprecated/disabled checks itself. Skip the
redundant check for enum members in the two name-resolution paths so the
diagnostic is emitted exactly once.

Author: PetarKirov

compiler/src/dmd/expressionsem.d

@@ -2703,7 +2703,9 @@ Lagain:
     {
         // functions are checked after overloading
         // templates are checked after matching constraints
-        if (!s.isFuncDeclaration() && !s.isTemplateDeclaration())
+        // enum members are checked once in getVarExp() below; skip here to avoid
+        // emitting the deprecation diagnostic twice for an enum member accessed by name
+        if (!s.isFuncDeclaration() && !s.isTemplateDeclaration() && !s.isEnumMember())
         {
             s.checkDeprecated(loc, sc);
             if (d)
@@ -2715,7 +2717,7 @@ Lagain:
         s = s.toAlias();
 
         //printf("s = '%s', s.kind = '%s', s.needThis() = %p\n", s.toChars(), s.kind(), s.needThis());
-        if (s != olds && !s.isFuncDeclaration() && !s.isTemplateDeclaration())
+        if (s != olds && !s.isFuncDeclaration() && !s.isTemplateDeclaration() && !s.isEnumMember())
         {
             s.checkDeprecated(loc, sc);
             if (d)
@@ -16006,14 +16008,18 @@ Expression dotIdSemanticProp(DotIdExp exp, Scope* sc, bool gag)
             // if 's' is a tuple variable, the tuple is returned.
             s = s.toAlias();
 
-            s.checkDeprecated(exp.loc, sc);
-            if (auto d = s.isDeclaration())
-                d.checkDisabled(exp.loc, sc);
-
             if (auto em = s.isEnumMember())
             {
+                // getVarExp() performs the deprecated/disabled checks itself; doing them
+                // here as well would emit the diagnostic twice for an enum member
+                // accessed by name (e.g. an anonymous enum member, or an ImportC enumerator).
                 return em.getVarExp(exp.loc, sc);
             }
+
+            s.checkDeprecated(exp.loc, sc);
+            if (auto d = s.isDeclaration())
+                d.checkDisabled(exp.loc, sc);
+
             if (auto v = s.isVarDeclaration())
             {
                 //printf("DotIdExp:: Identifier '%s' is a variable, type '%s'\n", toChars(), v.type.toErrMsg());

compiler/test/compilable/deprecated_enum_member.d

@@ -0,0 +1,53 @@
+/*
+REQUIRED_ARGS: -verrors=simple
+TEST_OUTPUT:
+---
+compilable/deprecated_enum_member.d(33): Deprecation: enum member `deprecated_enum_member.anon` is deprecated
+compilable/deprecated_enum_member.d(28):        `anon` is declared here
+compilable/deprecated_enum_member.d(36): Deprecation: enum member `deprecated_enum_member.E.named` is deprecated
+compilable/deprecated_enum_member.d(29):        `named` is declared here
+compilable/deprecated_enum_member.d(39): Deprecation: enum member `deprecated_enum_member.E.named` is deprecated
+compilable/deprecated_enum_member.d(29):        `named` is declared here
+compilable/deprecated_enum_member.d(42): Deprecation: enum member `deprecated_enum_member.F.withMsg` is deprecated - use namedB
+compilable/deprecated_enum_member.d(30):        `withMsg` is declared here
+compilable/deprecated_enum_member.d(43): Deprecation: enum member `deprecated_enum_member.F.withMsg` is deprecated - use namedB
+compilable/deprecated_enum_member.d(30):        `withMsg` is declared here
+compilable/deprecated_enum_member.d(47): Deprecation: enum member `deprecated_enum_member.anon` is deprecated
+compilable/deprecated_enum_member.d(28):        `anon` is declared here
+compilable/deprecated_enum_member.d(47): Deprecation: enum member `deprecated_enum_member.anon` is deprecated
+compilable/deprecated_enum_member.d(28):        `anon` is declared here
+---
+*/
+
+// A deprecated enum member must emit its deprecation diagnostic exactly once per
+// use, regardless of how it is named. Previously an enum member accessed by its
+// unqualified name (an anonymous-enum member, a member found via `with`, or an
+// ImportC enumerator) reported the deprecation twice, because the symbol was
+// checked both during name resolution and again in getVarExp(). See issue 23241.
+
+enum { deprecated anon = 0, anonB }
+enum E { deprecated named = 0, namedB }
+enum F { deprecated("use namedB") withMsg = 0, plain }
+
+// Anonymous enum member, accessed by its unqualified name.
+int useAnon() { return anon; }
+
+// Named enum member, accessed by its fully qualified name.
+int useNamedQualified() { return E.named; }
+
+// Named enum member, accessed by its unqualified name brought into scope by `with`.
+int useNamedWith() { E e; with (e) return named; }
+
+// A deprecated member carrying an explicit message reproduces that message.
+int useWithMsgQualified() { return F.withMsg; }
+int useWithMsgWith() { F f; with (f) return withMsg; }
+
+// Each separate use emits its own diagnostic (the fix removes a duplicate per use,
+// it does not globally deduplicate distinct uses).
+int useAnonAgain() { return anon + anon; }
+
+// Non-deprecated members of the same enums emit nothing.
+int useClean() { return anonB + E.namedB + F.plain; }
+
+// A use from within a deprecated scope is suppressed entirely.
+deprecated int useFromDeprecated() { return anon + E.named + F.withMsg; }