From c42e809f132d91fca1f96da2ecff7d78e1085c3f Mon Sep 17 00:00:00 2001
From: Andrew Kelley <superjoe30@gmail.com>
Date: Thu, 31 Aug 2017 16:54:20 -0400
Subject: [PATCH] setEvalBranchQuota must be called from top of comptime stack

---
 src/all_types.hpp       |  1 -
 src/ir.cpp              | 10 ++++++++--
 test/compile_errors.zig | 11 +++++++++++
 3 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/src/all_types.hpp b/src/all_types.hpp
index 9f1dc15a39..39e6033988 100644
--- a/src/all_types.hpp
+++ b/src/all_types.hpp
@@ -50,7 +50,6 @@ struct IrExecutable {
     size_t next_debug_id;
     size_t *backward_branch_count;
     size_t backward_branch_quota;
-    bool reported_quota_exceeded;
     bool invalid;
     ZigList<LabelTableEntry *> all_labels;
     ZigList<IrGotoItem> goto_list;
diff --git a/src/ir.cpp b/src/ir.cpp
index f8b6c4cdf7..74a48f6f50 100644
--- a/src/ir.cpp
+++ b/src/ir.cpp
@@ -7604,13 +7604,13 @@ static bool ir_emit_backward_branch(IrAnalyze *ira, IrInstruction *source_instru
     size_t *bbc = ira->new_irb.exec->backward_branch_count;
     size_t quota = ira->new_irb.exec->backward_branch_quota;
 
-    if (ira->new_irb.exec->reported_quota_exceeded) {
+    // If we're already over quota, we've already given an error message for this.
+    if (*bbc > quota) {
         return false;
     }
 
     *bbc += 1;
     if (*bbc > quota) {
-        ira->new_irb.exec->reported_quota_exceeded = true;
         ir_add_error(ira, source_instruction, buf_sprintf("evaluation exceeded %" ZIG_PRI_usize " backwards branches", quota));
         return false;
     }
@@ -13285,6 +13285,12 @@ static TypeTableEntry *ir_analyze_instruction_type_id(IrAnalyze *ira,
 static TypeTableEntry *ir_analyze_instruction_set_eval_branch_quota(IrAnalyze *ira,
         IrInstructionSetEvalBranchQuota *instruction)
 {
+    if (ira->new_irb.exec->parent_exec != nullptr) {
+        ir_add_error(ira, &instruction->base,
+                buf_sprintf("@setEvalBranchQuota must be called from the top of the comptime stack"));
+        return ira->codegen->builtin_types.entry_invalid;
+    }
+
     uint64_t new_quota;
     if (!ir_resolve_usize(ira, instruction->new_quota->other, &new_quota))
         return ira->codegen->builtin_types.entry_invalid;
diff --git a/test/compile_errors.zig b/test/compile_errors.zig
index 81d1361aec..2ab26c0078 100644
--- a/test/compile_errors.zig
+++ b/test/compile_errors.zig
@@ -2068,4 +2068,15 @@ pub fn addCases(cases: &tests.CompileErrorContext) {
     ,
         ".tmp_source.zig:2:24: error: expected [2]u8 literal, found [3]u8 literal");
 
+    cases.add("@setEvalBranchQuota in non-root comptime execution context",
+        \\comptime {
+        \\    foo();
+        \\}
+        \\fn foo() {
+        \\    @setEvalBranchQuota(1001);
+        \\}
+    ,
+        ".tmp_source.zig:5:5: error: @setEvalBranchQuota must be called from the top of the comptime stack",
+        ".tmp_source.zig:2:8: note: called from here",
+        ".tmp_source.zig:1:10: note: called from here");
 }