Fix #20889 - ImportC: Usage of typedef types decays to original type (#20904)

compiler/src/dmd/cparse.d

@@ -5526,6 +5526,12 @@ final class CParser(AST) : Parser!AST
             if (pt && *pt)
                 t = *pt;
         }
+        if (t.mcache && t.mcache.typedefIdent)
+        {
+            t = t.copy();
+            t.mcache = null;
+        }
+        t.getMcache().typedefIdent = id;
         auto tab = cast(void*[void*])(typedefTab[$ - 1]);
         tab[cast(void*)id] = cast(void*)t;
         typedefTab[$ - 1] = cast(void*)tab;

compiler/src/dmd/frontend.h

@@ -1830,6 +1830,7 @@ public:
         Type* pto;
         Type* rto;
         Type* arrayof;
+        Identifier* typedefIdent;
         Mcache() :
             cto(),
             ito(),
@@ -1841,10 +1842,11 @@ public:
             swcto(),
             pto(),
             rto(),
-            arrayof()
+            arrayof(),
+            typedefIdent()
         {
         }
-        Mcache(Type* cto, Type* ito = nullptr, Type* sto = nullptr, Type* scto = nullptr, Type* wto = nullptr, Type* wcto = nullptr, Type* swto = nullptr, Type* swcto = nullptr, Type* pto = nullptr, Type* rto = nullptr, Type* arrayof = nullptr) :
+        Mcache(Type* cto, Type* ito = nullptr, Type* sto = nullptr, Type* scto = nullptr, Type* wto = nullptr, Type* wcto = nullptr, Type* swto = nullptr, Type* swcto = nullptr, Type* pto = nullptr, Type* rto = nullptr, Type* arrayof = nullptr, Identifier* typedefIdent = nullptr) :
             cto(cto),
             ito(ito),
             sto(sto),
@@ -1855,7 +1857,8 @@ public:
             swcto(swcto),
             pto(pto),
             rto(rto),
-            arrayof(arrayof)
+            arrayof(arrayof),
+            typedefIdent(typedefIdent)
             {}
     };
 
@@ -4066,6 +4069,7 @@ struct HdrGenState final
     bool ddoc;
     bool fullDump;
     bool importcHdr;
+    bool inCAlias;
     bool doFuncBodies;
     bool vcg_ast;
     bool skipConstraints;
@@ -4084,6 +4088,7 @@ struct HdrGenState final
         ddoc(),
         fullDump(),
         importcHdr(),
+        inCAlias(),
         doFuncBodies(),
         vcg_ast(),
         skipConstraints(),
@@ -4099,11 +4104,12 @@ struct HdrGenState final
         inEnumDecl()
     {
     }
-    HdrGenState(bool hdrgen, bool ddoc = false, bool fullDump = false, bool importcHdr = false, bool doFuncBodies = false, bool vcg_ast = false, bool skipConstraints = false, bool showOneMember = true, bool errorMsg = false, bool fullQual = false, int32_t tpltMember = 0, int32_t autoMember = 0, int32_t forStmtInit = 0, int32_t insideFuncBody = 0, int32_t insideAggregate = 0, bool declstring = false, EnumDeclaration* inEnumDecl = nullptr) :
+    HdrGenState(bool hdrgen, bool ddoc = false, bool fullDump = false, bool importcHdr = false, bool inCAlias = false, bool doFuncBodies = false, bool vcg_ast = false, bool skipConstraints = false, bool showOneMember = true, bool errorMsg = false, bool fullQual = false, int32_t tpltMember = 0, int32_t autoMember = 0, int32_t forStmtInit = 0, int32_t insideFuncBody = 0, int32_t insideAggregate = 0, bool declstring = false, EnumDeclaration* inEnumDecl = nullptr) :
         hdrgen(hdrgen),
         ddoc(ddoc),
         fullDump(fullDump),
         importcHdr(importcHdr),
+        inCAlias(inCAlias),
         doFuncBodies(doFuncBodies),
         vcg_ast(vcg_ast),
         skipConstraints(skipConstraints),

compiler/src/dmd/hdrgen.d

@@ -59,6 +59,7 @@ struct HdrGenState
     bool ddoc;          /// true if generating Ddoc file
     bool fullDump;      /// true if generating a full AST dump file
     bool importcHdr;    /// true if generating a .di file from an ImportC file
+    bool inCAlias;      /// Set to prevent ImportC translating typedefs as `alias X = X`
     bool doFuncBodies;  /// include function bodies in output
     bool vcg_ast;       /// write out codegen-ast
     bool skipConstraints;  // skip constraints when doing templates
@@ -1777,7 +1778,9 @@ void toCBuffer(Dsymbol s, ref OutBuffer buf, ref HdrGenState hgs)
             buf.writestring(" = ");
             if (stcToBuffer(buf, d.storage_class))
                 buf.writeByte(' ');
+            hgs.inCAlias = hgs.importcHdr;
             typeToBuffer(d.type, null, buf, hgs);
+            hgs.inCAlias = false;
             hgs.declstring = false;
         }
         buf.writeByte(';');
@@ -4449,6 +4452,11 @@ private void typeToBufferx(Type t, ref OutBuffer buf, ref HdrGenState hgs)
         buf.writestring("noreturn");
     }
 
+    if (hgs.importcHdr && !hgs.inCAlias && t.mcache && t.mcache.typedefIdent)
+    {
+        buf.writestring(t.mcache.typedefIdent.toString());
+        return;
+    }
 
     switch (t.ty)
     {

compiler/src/dmd/mtype.d

@@ -302,6 +302,10 @@ extern (C++) abstract class Type : ASTNode
         Type pto;       // merged pointer to this type
         Type rto;       // reference to this type
         Type arrayof;   // array of this type
+
+        // ImportC: store the name of the typedef resolving to this type
+        // So `uint8_t x;` will be printed as `uint8_t x;` and not as the resolved `ubyte x;`
+        Identifier typedefIdent;
     }
     Mcache* mcache;
 

compiler/test/compilable/ctod.i

@@ -41,6 +41,18 @@ extern (C)
 		int x = void;
 	}
 	alias weird = int[(cast(foo*)cast(void*)0).x.sizeof];
+	alias ULONG = ulong;
+	alias ULONG_Deluxe = ulong;
+	alias ULONG_PTR = ulong*;
+	alias Callback = void* function();
+	struct Test
+	{
+		ULONG_Deluxe d = void;
+		ULONG_Deluxe* p = void;
+		ULONG_PTR q = void;
+		Callback cb = void;
+	}
+	extern __gshared int[cast(ULONG)3] arr;
 	/+enum int __DATE__ = 1+/;
 	/+enum int __TIME__ = 1+/;
 	/+enum int __TIMESTAMP__ = 1+/;
@@ -96,3 +108,19 @@ struct foo {
     int x;
 };
 typedef int weird[sizeof(((struct foo *)((void*)0))->x)];
+
+// https://github.com/dlang/dmd/issues/20889
+typedef unsigned long long ULONG;
+typedef ULONG ULONG_Deluxe;
+typedef ULONG_Deluxe *ULONG_PTR;
+typedef void *(*Callback)();
+
+struct Test
+{
+	ULONG_Deluxe d;
+	ULONG_Deluxe *p;
+	ULONG_PTR q;
+	Callback cb;
+};
+
+int arr[(ULONG) 3];