4 files changed, 31 insertions, 23 deletions

diff --git a/src/all_types.hpp b/src/all_types.hpp
index d5b24b121d..71bc596f81 100644
--- a/src/all_types.hpp
+++ b/src/all_types.hpp
@@ -1174,6 +1174,7 @@ enum BuiltinFnId {
     BuiltinFnIdDivExact,
     BuiltinFnIdTruncate,
     BuiltinFnIdIntType,
+    BuiltinFnIdUnreachable,
 };
 
 struct BuiltinFnEntry {
diff --git a/src/analyze.cpp b/src/analyze.cpp
index 3ed246d1b5..b39bc584ac 100644
--- a/src/analyze.cpp
+++ b/src/analyze.cpp
@@ -2677,13 +2677,6 @@ static TypeTableEntry *analyze_container_init_expr(CodeGen *g, ImportTableEntry
         } else {
             return resolve_expr_const_val_as_void(g, node);
         }
-    } else if (container_type->id == TypeTableEntryIdUnreachable) {
-        if (container_init_expr->entries.length != 0) {
-            add_node_error(g, node, buf_sprintf("unreachable expression expects no arguments"));
-            return g->builtin_types.entry_invalid;
-        } else {
-            return container_type;
-        }
     } else {
         add_node_error(g, node,
             buf_sprintf("type '%s' does not support %s initialization syntax",
@@ -5435,6 +5428,8 @@ static TypeTableEntry *analyze_builtin_fn_call_expr(CodeGen *g, ImportTableEntry
             return analyze_compile_err(g, import, context, node);
         case BuiltinFnIdIntType:
             return analyze_int_type(g, import, context, node);
+        case BuiltinFnIdUnreachable:
+            return g->builtin_types.entry_unreachable;
     }
     zig_unreachable();
 }
diff --git a/src/codegen.cpp b/src/codegen.cpp
index 41a1a394cd..ddf06b7eef 100644
--- a/src/codegen.cpp
+++ b/src/codegen.cpp
@@ -497,6 +497,20 @@ static LLVMValueRef gen_truncate(CodeGen *g, AstNode *node) {
     return LLVMBuildTrunc(g->builder, src_val, dest_type->type_ref, "");
 }
 
+static LLVMValueRef gen_unreachable(CodeGen *g, AstNode *node) {
+    assert(node->type == NodeTypeFnCallExpr);
+
+    set_debug_source_node(g, node);
+
+    if (want_debug_safety(g, node) || g->is_test_build) {
+        gen_debug_safety_crash(g);
+    } else {
+        LLVMBuildUnreachable(g->builder);
+    }
+
+    return nullptr;
+}
+
 static LLVMValueRef gen_shl_with_overflow(CodeGen *g, AstNode *node) {
     assert(node->type == NodeTypeFnCallExpr);
 
@@ -689,6 +703,8 @@ static LLVMValueRef gen_builtin_fn_call_expr(CodeGen *g, AstNode *node) {
             return gen_div_exact(g, node);
         case BuiltinFnIdTruncate:
             return gen_truncate(g, node);
+        case BuiltinFnIdUnreachable:
+            return gen_unreachable(g, node);
     }
     zig_unreachable();
 }
@@ -2949,15 +2965,6 @@ static LLVMValueRef gen_container_init_expr(CodeGen *g, AstNode *node) {
         }
 
         return tmp_struct_ptr;
-    } else if (type_entry->id == TypeTableEntryIdUnreachable) {
-        assert(node->data.container_init_expr.entries.length == 0);
-        set_debug_source_node(g, node);
-        if (want_debug_safety(g, node) || g->is_test_build) {
-            gen_debug_safety_crash(g);
-        } else {
-            LLVMBuildUnreachable(g->builder);
-        }
-        return nullptr;
     } else if (type_entry->id == TypeTableEntryIdVoid) {
         assert(node->data.container_init_expr.entries.length == 0);
         return nullptr;
@@ -4859,6 +4866,7 @@ static void define_builtin_fns(CodeGen *g) {
     create_builtin_fn_with_arg_count(g, BuiltinFnIdTruncate, "truncate", 2);
     create_builtin_fn_with_arg_count(g, BuiltinFnIdCompileErr, "compileError", 1);
     create_builtin_fn_with_arg_count(g, BuiltinFnIdIntType, "intType", 2);
+    create_builtin_fn_with_arg_count(g, BuiltinFnIdUnreachable, "unreachable", 0);
 }
 
 static void init(CodeGen *g, Buf *source_path) {
diff --git a/src/eval.cpp b/src/eval.cpp
index 1e71fd262b..79d3079adc 100644
--- a/src/eval.cpp
+++ b/src/eval.cpp
@@ -491,13 +491,6 @@ static bool eval_container_init_expr(EvalFn *ef, AstNode *node, ConstExprValue *
         }
     } else if (container_type->id == TypeTableEntryIdVoid) {
         return false;
-    } else if (container_type->id == TypeTableEntryIdUnreachable) {
-        ef->root->abort = true;
-        ErrorMsg *msg = add_node_error(ef->root->codegen, ef->root->fn->fn_def_node,
-                buf_sprintf("function evaluation reached unreachable expression"));
-        add_error_note(ef->root->codegen, msg, ef->root->call_node, buf_sprintf("called from here"));
-        add_error_note(ef->root->codegen, msg, node, buf_sprintf("unreachable expression here"));
-        return true;
     } else if (container_type->id == TypeTableEntryIdStruct &&
                container_type->data.structure.is_slice &&
                kind == ContainerInitKindArray)
@@ -791,6 +784,15 @@ static bool eval_div_exact(EvalFn *ef, AstNode *node, ConstExprValue *out_val) {
     return false;
 }
 
+static bool eval_unreachable(EvalFn *ef, AstNode *node, ConstExprValue *out_val) {
+    ef->root->abort = true;
+    ErrorMsg *msg = add_node_error(ef->root->codegen, ef->root->fn->fn_def_node,
+            buf_sprintf("function evaluation reached unreachable expression"));
+    add_error_note(ef->root->codegen, msg, ef->root->call_node, buf_sprintf("called from here"));
+    add_error_note(ef->root->codegen, msg, node, buf_sprintf("unreachable expression here"));
+    return true;
+}
+
 static bool eval_fn_with_overflow(EvalFn *ef, AstNode *node, ConstExprValue *out_val,
     bool (*bignum_fn)(BigNum *dest, BigNum *op1, BigNum *op2))
 {
@@ -851,6 +853,8 @@ static bool eval_fn_call_builtin(EvalFn *ef, AstNode *node, ConstExprValue *out_
             return false;
         case BuiltinFnIdDivExact:
             return eval_div_exact(ef, node, out_val);
+        case BuiltinFnIdUnreachable:
+            return eval_unreachable(ef, node, out_val);
         case BuiltinFnIdMemcpy:
         case BuiltinFnIdMemset:
         case BuiltinFnIdSizeof: