Fix #22584 - unexpected deprecation on duplicate foreach vars

changelog/dmd.foreach-shadow-error.dd

@@ -0,0 +1,32 @@
+Foreach variable shadowing is now an error
+
+A deprecation introduced in DMD 2.089.0 for foreach variables shadowing
+outer scope symbols has been upgraded to an error.
+
+This affects both variables declared inside a foreach body that shadow
+outer variables, and duplicate variable names in foreach parameter lists
+when using `opApply`.
+
+---
+void main()
+{
+    int[int] arr;
+    int x;
+    foreach (i, j; arr)
+    {
+        int x; // Error: variable `x` is shadowing variable `...x`
+    }
+}
+---
+
+---
+struct Foo
+{
+    int opApply(scope int delegate(size_t, size_t, ref uint)) => 0;
+}
+
+void main()
+{
+    foreach (x, y, x; Foo()) {} // Error: variable `x` is shadowing variable `...x`
+}
+---

compiler/src/dmd/expressionsem.d

@@ -8731,17 +8731,10 @@ private extern (C++) final class ExpressionSemanticVisitor : Visitor
                         auto decl = s2.isDeclaration();
                         if (decl && (decl.storage_class & STC.local))
                             continue;
-                        if (sc.func.fes)
-                        {
-                            deprecation(e.loc, "%s `%s` is shadowing %s `%s`", s.kind(), s.ident.toChars(), s2.kind(), s2.toPrettyChars());
-                            deprecationSupplemental(s2.loc, "declared here");
-                        }
-                        else
-                        {
-                            error(e.loc, "%s `%s` is shadowing %s `%s`", s.kind(), s.ident.toChars(), s2.kind(), s2.toPrettyChars());
-                            errorSupplemental(s2.loc, "declared here");
+                        error(e.loc, "%s `%s` is shadowing %s `%s`", s.kind(), s.ident.toChars(), s2.kind(), s2.toPrettyChars());
+                        errorSupplemental(s2.loc, "declared here");
+                        if (!sc.func.fes)
                             return setError();
-                        }
                     }
                 }
             }

compiler/test/fail_compilation/fail2195.d

@@ -1,10 +1,9 @@
 // https://issues.dlang.org/show_bug.cgi?id=2195
-// REQUIRED_ARGS: -de
 /*
 TEST_OUTPUT:
 ---
-fail_compilation/fail2195.d(17): Deprecation: variable `variable` is shadowing variable `fail2195.main.variable`
-fail_compilation/fail2195.d(14):        declared here
+fail_compilation/fail2195.d(16): Error: variable `variable` is shadowing variable `fail2195.main.variable`
+fail_compilation/fail2195.d(13):        declared here
 ---
 */
 

compiler/test/fail_compilation/fail22584.d

@@ -0,0 +1,15 @@
+// https://github.com/dlang/dmd/issues/22584
+/*
+TEST_OUTPUT:
+---
+fail_compilation/fail22584.d(14): Error: variable `x` is shadowing variable `fail22584.main.__foreachbody_L14_C5.x`
+fail_compilation/fail22584.d(14):        declared here
+---
+*/
+
+struct Foo {
+    int opApply(scope int delegate(size_t, size_t, ref uint)) => 0;
+}
+void main() {
+    foreach (x, y, x; Foo()) {}
+}