Commit 8e4d0ae4f5

@@ -8180,7 +8180,7 @@ fn analyzeParameter(
     if (param.is_comptime and !Type.fnCallingConventionAllowsZigTypes(cc)) {
         return sema.fail(block, param_src, "comptime parameters not allowed in function with calling convention '{s}'", .{@tagName(cc)});
     }
-    if (this_generic and !Type.fnCallingConventionAllowsZigTypes(cc)) {
+    if (this_generic and !sema.no_partial_func_ty and !Type.fnCallingConventionAllowsZigTypes(cc)) {
         return sema.fail(block, param_src, "generic parameters not allowed in function with calling convention '{s}'", .{@tagName(cc)});
     }
     if (!param.ty.isValidParamType()) {
@@ -8196,7 +8196,7 @@ fn analyzeParameter(
         };
         return sema.failWithOwnedErrorMsg(msg);
     }
-    if (!Type.fnCallingConventionAllowsZigTypes(cc) and !try sema.validateExternType(block, param_src, param.ty, .param_ty)) {
+    if (!this_generic and !Type.fnCallingConventionAllowsZigTypes(cc) and !try sema.validateExternType(block, param_src, param.ty, .param_ty)) {
         const msg = msg: {
             const msg = try sema.errMsg(block, param_src, "parameter of type '{}' not allowed in function with calling convention '{s}'", .{
                 param.ty.fmt(sema.mod), @tagName(cc),

@@ -0,0 +1,13 @@
+const std = @import("std");
+const expect = std.testing.expect;
+
+fn A(
+    comptime T: type,
+    comptime destroycb: ?*const fn (?*T) callconv(.C) void,
+) !void {
+    try expect(destroycb == null);
+}
+
+test {
+    try A(u32, null);
+}

@@ -96,6 +96,7 @@ test {
     _ = @import("behavior/bugs/12885.zig");
     _ = @import("behavior/bugs/12911.zig");
     _ = @import("behavior/bugs/12928.zig");
+    _ = @import("behavior/bugs/12945.zig");
     _ = @import("behavior/byteswap.zig");
     _ = @import("behavior/byval_arg_var.zig");
     _ = @import("behavior/call.zig");