feat: formatting strings at runtime

src/Sema.zig

@@ -425,6 +425,30 @@ fn irStr(sema: *Sema, inst: Ir.Inst.Index) InnerError!ValueInfo {
     return .{ .value = ip_index };
 }
 
+fn irStrFormat(
+    sema: *Sema,
+    builder: *Builder,
+    _: *Block,
+    inst: Ir.Inst.Index,
+) InnerError!ValueInfo {
+    const data = sema.ir.instructions[@intFromEnum(inst)].data.payload;
+    const extra = sema.ir.extraData(Ir.Inst.MultiOp, data.extra_index);
+    const args_slice = sema.ir.refSlice(extra.end, extra.data.operands_len);
+
+    try builder.addByteOp(.string_builder);
+
+    var index: usize = 0;
+    while (index < args_slice.len) : (index += 1) {
+        const arg = args_slice[index];
+        const arg_inst = sema.resolveInst(arg);
+        try builder.ensureLoad(arg_inst);
+        try builder.addByteOp(.string_append);
+    }
+
+    try builder.addByteOp(.string_freeze);
+    return .stack;
+}
+
 fn irUnaryOp(
     sema: *Sema,
     builder: *Builder,
@@ -1081,6 +1105,7 @@ fn analyzeBodyInner(
             .int => try irInt(sema, inst),
             .float => try irFloat(sema, inst),
             .str => try irStr(sema, inst),
+            .str_format => try irStrFormat(sema, builder, block, inst),
             .add => try irBinaryOp(sema, builder, inst, .add),
             .sub => try irBinaryOp(sema, builder, inst, .sub),
             .mul => try irBinaryOp(sema, builder, inst, .mul),