Merge #2144 (198fe482) into the footprint pull request

# Conflicts:
#	docs/macros.md

crates/engine/src/macros/run.rs

@@ -520,7 +520,8 @@ impl Guard {
             if Arc::ptr_eq(ps, sa) {
                 continue;
             }
-            let in_input = |c: CellRef| inputs.iter().any(|(_, p, _)| p.sheet == si && p.range.contains(c));
+            // The inputs have followed their cells, so they are on the sheet's index now.
+            let in_input = |c: CellRef| inputs.iter().any(|(_, p, _)| p.sheet == ai && p.range.contains(c));
             let mut hit: Vec<CellRef> = ps
                 .cells
                 .diff(&sa.cells)

crates/engine/src/tests/macros.rs

@@ -205,10 +205,21 @@ fn inputs_and_the_output_follow_their_cells_when_a_step_moves_them() {
         {"command": "home.insertSheet", "params": {"name": "Summary", "before": 0}},
         {"command": "cell.set", "params": {"cell": "Input", "input": "x"}}
     ]);
-    put(&mut s, json!({"name": "Front", "inputs": [{"name": "Input", "kind": "cell"}], "output": {"onConflict": "overwrite"}, "steps": steps}));
+    put(
+        &mut s,
+        json!({"name": "Front", "inputs": [{"name": "Input", "kind": "cell"}], "output": {"onConflict": "overwrite"}, "steps": steps.clone()}),
+    );
     s.execute("macro.run", json!({"name": "Front", "inputs": "Sheet1!B2"})).unwrap();
     assert_eq!((on(&s, "Sheet1", "B2"), on(&s, "Summary", "B2")), ("x".into(), "".into()));
 
+    // Data in the input: the step writes into its own input, which isn't data written over, on
+    // the input's sheet wherever it moved.
+    let mut s = super::s();
+    set(&mut s, "B2", "held");
+    put(&mut s, json!({"name": "Front", "inputs": [{"name": "Input", "kind": "cell"}], "output": {"onConflict": "fail"}, "steps": steps}));
+    s.execute("macro.run", json!({"name": "Front", "inputs": "Sheet1!B2"})).unwrap();
+    assert_eq!(on(&s, "Sheet1", "B2"), "x");
+
     // Rows inserted above: the input and the output move down with their cells.
     let mut s = super::s();
     set(&mut s, "B5", "in");

docs/macros.md

@@ -9,8 +9,11 @@ error (a file it already wrote stays), checks where its results will land before
 and does not touch files without permission.
 Agents run macros with `macro.run` like any other command.
 
-This page describes the macro format, its tokens, and running and checking macros. The engine has
-no macro debugger, recorder or management commands in this version, and no macro interface.
+This page describes the macro format, its tokens, and running and checking macros. `macro.run`
+checks the macro, its inputs, its parameters and the policy before it runs, works out where it
+writes, and checks each step as it runs; `macro.check` reports what a run would do without
+running it. The engine has no macro debugger, recorder or management commands in this version,
+and no macro interface.
 
 ## A macro
 
@@ -123,8 +126,9 @@ refused rather than read as the header.
    or objects that held data when the run started stops the run and rolls the workbook back (a
    file already written stays): it asks (`confirm: …`) under `ask` and fails otherwise, since
    shifting can't make room that late. Moving cells that hold data, as inserting or deleting rows
-   or cells above them does, counts as writing over them, in the footprint and in this check:
-   both compare cells by place.
+   or cells above them does, counts as writing over them, in the footprint and in this check, and
+   so does a formula whose references such a move rewrites: both compare cells by place, so they
+   may ask about data that only moved, never the other way.
 3. **Run.** One undo step, "Run Macro: Totals". Any error rolls the whole run back and names the
    step: `Step 3.1 (cell.set): …` (paths are 1-based; `2.1` is inside a Repeat, `4.then.1` inside
    an If). The message ends "Nothing was changed.", or names the files the run already wrote,