export: check variable type

also fixed existing occurrences

src-self-hosted/stage1.zig

@@ -428,11 +428,11 @@ export fn stage2_DepTokenizer_next(self: *stage2_DepTokenizer) stage2_DepNextRes
     };
 }
 
-export const stage2_DepTokenizer = extern struct {
+const stage2_DepTokenizer = extern struct {
     handle: *DepTokenizer,
 };
 
-export const stage2_DepNextResult = extern struct {
+const stage2_DepNextResult = extern struct {
     type_id: TypeId,
 
     // when type_id == error --> error text
@@ -441,7 +441,7 @@ export const stage2_DepNextResult = extern struct {
     // when type_id == prereq --> prereq pathname
     textz: [*]const u8,
 
-    export const TypeId = extern enum {
+    const TypeId = extern enum {
         error_,
         null_,
         target,

src/analyze.cpp

@@ -3773,6 +3773,16 @@ ZigVar *add_variable(CodeGen *g, AstNode *source_node, Scope *parent_scope, Buf
     return variable_entry;
 }
 
+static void validate_export_var_type(CodeGen *g, ZigType* type, AstNode *source_node) {
+    switch (type->id) {
+        case ZigTypeIdMetaType:
+            add_node_error(g, source_node, buf_sprintf("cannot export variable of type 'type'"));
+            break;
+        default:
+            break;
+    }
+}
+
 static void resolve_decl_var(CodeGen *g, TldVar *tld_var, bool allow_lazy) {
     AstNode *source_node = tld_var->base.source_node;
     AstNodeVariableDeclaration *var_decl = &source_node->data.variable_declaration;
@@ -3862,6 +3872,7 @@ static void resolve_decl_var(CodeGen *g, TldVar *tld_var, bool allow_lazy) {
     }
 
     if (is_export) {
+        validate_export_var_type(g, type, source_node);
         add_var_export(g, tld_var->var, tld_var->var->name, GlobalLinkageIdStrong);
     }
 

test/gen_h.zig

@@ -74,7 +74,7 @@ pub fn addCases(cases: *tests.GenHContext) void {
     );
 
     cases.add("declare opaque type",
-        \\export const Foo = @OpaqueType();
+        \\const Foo = @OpaqueType();
         \\
         \\export fn entry(foo: ?*Foo) void { }
     ,