From 3666fbd9f9465ba2ae70b178106e5d9e3cea68ca Mon Sep 17 00:00:00 2001
From: Andrew Kelley <superjoe30@gmail.com>
Date: Wed, 14 Nov 2018 12:23:40 -0500
Subject: [PATCH] ** and ++ operators force comptime on operands

closes #1707
---
 src/ir.cpp          |  9 +++++++--
 test/cases/eval.zig | 18 ++++++++++++++++++
 2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/src/ir.cpp b/src/ir.cpp
index 0d1cbd04dd..128b53fc2d 100644
--- a/src/ir.cpp
+++ b/src/ir.cpp
@@ -3182,8 +3182,13 @@ static IrInstruction *ir_gen_block(IrBuilder *irb, Scope *parent_scope, AstNode
 }
 
 static IrInstruction *ir_gen_bin_op_id(IrBuilder *irb, Scope *scope, AstNode *node, IrBinOp op_id) {
-    IrInstruction *op1 = ir_gen_node(irb, node->data.bin_op_expr.op1, scope);
-    IrInstruction *op2 = ir_gen_node(irb, node->data.bin_op_expr.op2, scope);
+    Scope *inner_scope = scope;
+    if (op_id == IrBinOpArrayCat || op_id == IrBinOpArrayMult) {
+        inner_scope = create_comptime_scope(irb->codegen, node, scope);
+    }
+
+    IrInstruction *op1 = ir_gen_node(irb, node->data.bin_op_expr.op1, inner_scope);
+    IrInstruction *op2 = ir_gen_node(irb, node->data.bin_op_expr.op2, inner_scope);
 
     if (op1 == irb->codegen->invalid_instruction || op2 == irb->codegen->invalid_instruction)
         return irb->codegen->invalid_instruction;
diff --git a/test/cases/eval.zig b/test/cases/eval.zig
index 408e9b04af..a9eded151e 100644
--- a/test/cases/eval.zig
+++ b/test/cases/eval.zig
@@ -762,3 +762,21 @@ test "*align(1) u16 is the same as *align(1:0:2) u16" {
         //assert(*align(:0:2) u16 == *u16);
     }
 }
+
+test "array concatenation forces comptime" {
+    var a = oneItem(3) ++ oneItem(4);
+    assert(std.mem.eql(i32, a, []i32{3, 4}));
+}
+
+test "array multiplication forces comptime" {
+    var a = oneItem(3) ** scalar(2);
+    assert(std.mem.eql(i32, a, []i32{3, 3}));
+}
+
+fn oneItem(x: i32) [1]i32 {
+    return []i32{x};
+}
+
+fn scalar(x: u32) u32 {
+    return x;
+}