From 04076c39f7a94cade9c5a42036d024ab8ab79220 Mon Sep 17 00:00:00 2001
From: Mindy Batek <desisma@heidel.beer>
Date: Tue, 26 May 2026 02:25:55 +0200
Subject: [PATCH 1/2] Implement trait `getBuiltIn`

---
 compiler/src/dmd/frontend.h |  1 +
 compiler/src/dmd/id.d       |  1 +
 compiler/src/dmd/traits.d   | 38 ++++++++++++++++++++++++++++++++++++-
 3 files changed, 39 insertions(+), 1 deletion(-)

diff --git a/compiler/src/dmd/frontend.h b/compiler/src/dmd/frontend.h
index dbdc758be9..9d0dbeabef 100644
--- a/compiler/src/dmd/frontend.h
+++ b/compiler/src/dmd/frontend.h
@@ -8844,6 +8844,7 @@ struct Id final
     static Identifier* outp;
     static Identifier* outpl;
     static Identifier* outpw;
+    static Identifier* getBuiltIn;
     static Identifier* isAbstractClass;
     static Identifier* isArithmetic;
     static Identifier* isAssociativeArray;
diff --git a/compiler/src/dmd/id.d b/compiler/src/dmd/id.d
index 51d850fa6d..cf62f2cabb 100644
--- a/compiler/src/dmd/id.d
+++ b/compiler/src/dmd/id.d
@@ -456,6 +456,7 @@ immutable Msgtable[] msgtable =
     { "outpw"},
 
     // Traits
+    { "getBuiltIn" },
     { "isAbstractClass" },
     { "isArithmetic" },
     { "isAssociativeArray" },
diff --git a/compiler/src/dmd/traits.d b/compiler/src/dmd/traits.d
index cd49e51189..358fe4092f 100644
--- a/compiler/src/dmd/traits.d
+++ b/compiler/src/dmd/traits.d
@@ -440,6 +440,41 @@ Expression semanticTraits(TraitsExp e, Scope* sc)
         });
     }
 
+    if (e.ident == Id.getBuiltIn)
+    {
+        if (dim != 1)
+            return dimError(1);
+
+        auto exNeedle = isExpression((*e.args)[0]);
+        if (!exNeedle)
+        {
+            error(e.loc, "expression expected as first argument of __traits `%s`", e.ident.toChars());
+            return ErrorExp.get();
+        }
+        exNeedle = exNeedle.ctfeInterpret();
+
+        StringExp seNeedle = exNeedle.toStringExp();
+        if (!seNeedle || seNeedle.len == 0)
+        {
+            error(e.loc, "string expected as first argument of __traits `%s` instead of `%s`", e.ident.toChars(), exNeedle.toChars());
+            return ErrorExp.get();
+        }
+        seNeedle = seNeedle.toUTF8(sc);
+
+        if (seNeedle.sz != 1)
+        {
+            error(e.loc, "string must be chars");
+            return ErrorExp.get();
+        }
+        const builtInName = seNeedle.peekString();
+
+        switch(builtInName)
+        {
+        default:
+            error(e.loc, "`%.*s` is not a retrievable built-in", cast(int) builtInName.length, builtInName.ptr);
+            return ErrorExp.get();
+        }
+    }
     if (e.ident == Id.isArithmetic)
     {
         return isTypeX(t => t.isintegral() || t.isfloating());
@@ -2499,7 +2534,7 @@ private void traitNotFound(TraitsExp e) @system
         initialized = true;     // lazy initialization
 
         // All possible traits
-        __gshared Identifier*[62] idents =
+        __gshared Identifier*[63] idents =
         [
             &Id.allMembers,
             &Id.child,
@@ -2510,6 +2545,7 @@ private void traitNotFound(TraitsExp e) @system
             &Id.fullyQualifiedName,
             &Id.getAliasThis,
             &Id.getAttributes,
+            &Id.getBuiltIn,
             &Id.getFunctionAttributes,
             &Id.getFunctionVariadicStyle,
             &Id.getLinkage,

From 86b813b7c9655d4e3bfd0ee664c2518ec0345e22 Mon Sep 17 00:00:00 2001
From: Mindy Batek <desisma@heidel.beer>
Date: Tue, 26 May 2026 03:29:44 +0200
Subject: [PATCH 2/2] Add integer types to trait `getBuiltIn`

---
 compiler/src/dmd/traits.d | 38 +++++++++++++++++++++++++++++++-------
 1 file changed, 31 insertions(+), 7 deletions(-)

diff --git a/compiler/src/dmd/traits.d b/compiler/src/dmd/traits.d
index 358fe4092f..a07af5c145 100644
--- a/compiler/src/dmd/traits.d
+++ b/compiler/src/dmd/traits.d
@@ -467,13 +467,7 @@ Expression semanticTraits(TraitsExp e, Scope* sc)
             return ErrorExp.get();
         }
         const builtInName = seNeedle.peekString();
-
-        switch(builtInName)
-        {
-        default:
-            error(e.loc, "`%.*s` is not a retrievable built-in", cast(int) builtInName.length, builtInName.ptr);
-            return ErrorExp.get();
-        }
+        return resolveGetBuiltIn(builtInName, e.loc);
     }
     if (e.ident == Id.isArithmetic)
     {
@@ -2626,3 +2620,33 @@ private void traitNotFound(TraitsExp e) @system
     else
         error(e.loc, "unrecognized trait `%s`", e.ident.toChars());
 }
+
+private Expression resolveGetBuiltIn(const(char)[] name, Loc loc)
+{
+    // Signed integer types
+    if (name.iequals("int8"))
+        return new TypeExp(loc, Type.tint8);
+    if (name.iequals("int16"))
+        return new TypeExp(loc, Type.tint16);
+    if (name.iequals("int32"))
+        return new TypeExp(loc, Type.tint32);
+    if (name.iequals("int64"))
+        return new TypeExp(loc, Type.tint64);
+    if (name.iequals("int128"))
+        return new TypeExp(loc, Type.tint128);
+
+    // Unsigned integer types
+    if (name.iequals("uint8"))
+        return new TypeExp(loc, Type.tuns8);
+    if (name.iequals("uint16"))
+        return new TypeExp(loc, Type.tuns16);
+    if (name.iequals("uint32"))
+        return new TypeExp(loc, Type.tuns32);
+    if (name.iequals("uint64"))
+        return new TypeExp(loc, Type.tuns64);
+    if (name.iequals("uint128"))
+        return new TypeExp(loc, Type.tuns128);
+
+    error(loc, "`%.*s` is not a retrievable built-in", cast(int) name.length, name.ptr);
+    return ErrorExp.get();
+}