fix enum codegen and implement comptime switch var on enums

src/codegen.cpp

@@ -677,9 +677,14 @@ static LLVMValueRef ir_llvm_value(CodeGen *g, IrInstruction *instruction) {
         assert(instruction->value.special != ConstValSpecialRuntime);
         assert(instruction->value.type);
         render_const_val(g, &instruction->value);
+        // we might have to do some pointer casting here due to the way union
+        // values are rendered with a type other than the one we expect
         if (handle_is_ptr(instruction->value.type)) {
             render_const_val_global(g, &instruction->value);
-            instruction->llvm_value = instruction->value.llvm_global;
+            TypeTableEntry *ptr_type = get_pointer_to_type(g, instruction->value.type, true);
+            instruction->llvm_value = LLVMBuildBitCast(g->builder, instruction->value.llvm_global, ptr_type->type_ref, "");
+        } else if (instruction->value.type->id == TypeTableEntryIdPointer) {
+            instruction->llvm_value = LLVMBuildBitCast(g->builder, instruction->value.llvm_value, instruction->value.type->type_ref, "");
         } else {
             instruction->llvm_value = instruction->value.llvm_value;
         }
@@ -2540,7 +2545,7 @@ static LLVMValueRef gen_const_val(CodeGen *g, ConstExprValue *const_val) {
                         tag_value,
                         union_value,
                     };
-                    return LLVMConstNamedStruct(canon_type->type_ref, fields, 2);
+                    return LLVMConstStruct(fields, 2, false);
                 }
             }
         case TypeTableEntryIdFn:
@@ -2553,11 +2558,7 @@ static LLVMValueRef gen_const_val(CodeGen *g, ConstExprValue *const_val) {
                     render_const_val(g, const_val->data.x_ptr.base_ptr);
                     render_const_val_global(g, const_val->data.x_ptr.base_ptr);
                     ConstExprValue *other_val = const_val->data.x_ptr.base_ptr;
-                    if (other_val->type == const_val->type->data.pointer.child_type) {
+                    const_val->llvm_value = LLVMConstBitCast(other_val->llvm_global, const_val->type->type_ref);
-                        const_val->llvm_value = other_val->llvm_global;
-                    } else {
-                        const_val->llvm_value = LLVMConstBitCast(other_val->llvm_global, const_val->type->type_ref);
-                    }
                     render_const_val_global(g, const_val);
                     return const_val->llvm_value;
                 } else {
@@ -2636,7 +2637,8 @@ static void render_const_val(CodeGen *g, ConstExprValue *const_val) {
 
 static void render_const_val_global(CodeGen *g, ConstExprValue *const_val) {
     if (!const_val->llvm_global) {
-        LLVMValueRef global_value = LLVMAddGlobal(g->module, const_val->type->type_ref, "");
+        LLVMTypeRef type_ref = const_val->llvm_value ? LLVMTypeOf(const_val->llvm_value) : const_val->type->type_ref;
+        LLVMValueRef global_value = LLVMAddGlobal(g->module, type_ref, "");
         LLVMSetLinkage(global_value, LLVMInternalLinkage);
         LLVMSetGlobalConstant(global_value, true);
         LLVMSetUnnamedAddr(global_value, true);

src/ir.cpp

@@ -9565,7 +9565,20 @@ static TypeTableEntry *ir_analyze_instruction_switch_var(IrAnalyze *ira, IrInstr
         }
 
         if (instr_is_comptime(target_value_ptr)) {
-            zig_panic("TODO comptime switch var");
+            ConstExprValue *target_val_ptr = ir_resolve_const(ira, target_value_ptr, UndefBad);
+            if (!target_value_ptr)
+                return ira->codegen->builtin_types.entry_invalid;
+
+            ConstExprValue *pointee_val = const_ptr_pointee(target_val_ptr);
+            if (pointee_val->type->id == TypeTableEntryIdEnum) {
+                bool depends_on_compile_var = target_value_ptr->value.depends_on_compile_var;
+                ConstExprValue *out_val = ir_build_const_from(ira, &instruction->base, depends_on_compile_var);
+                out_val->data.x_ptr.base_ptr = pointee_val->data.x_enum.payload;
+                out_val->data.x_ptr.index = SIZE_MAX;
+                return get_pointer_to_type(ira->codegen, pointee_val->type, target_value_ptr->value.type->data.pointer.is_const);
+            } else {
+                zig_panic("TODO comptime switch var");
+            }
         }
 
         ir_build_enum_field_ptr_from(&ira->new_irb, &instruction->base, target_value_ptr, field);

test/cases/switch.zig

@@ -129,3 +129,25 @@ fn switchWithMultipleExpressions() {
 fn returnsFive() -> i32 {
     5
 }
+
+
+const Number = enum {
+    One: u64,
+    Two: u8,
+    Three: f32,
+};
+
+const number = Number.Three { 1.23 };
+
+fn returnsFalse() -> bool {
+    switch (number) {
+        Number.One => |x| return x > 1234,
+        Number.Two => |x| return x == 'a',
+        Number.Three => |x| return x > 12.34,
+    }
+}
+fn switchOnConstEnumWithVar() {
+    @setFnTest(this);
+
+    assert(!returnsFalse());
+}