[NNX] Checkpoint restore: name the parameter path on ShapeDtypeStruct mismatch

[ecnal-cienet]

Description

When Orbax skips a parameter during an NNX checkpoint restore (a structural/shape mismatch under partial_restore), it leaves an unmaterialized jax.ShapeDtypeStruct in the restored state. Today the guard that catches this reports only the raw struct, so the failure surfaces as a cryptic, low-level compile/allocation error deep in the first train_step.

This makes _assert_no_shaped_dtype_struct carry the tree path and report the offending parameter and its shape/dtype, pointing straight at the config that doesn't match the checkpoint (e.g. emb_dim, mlp_dim, num layers, scan_layers).

Tests

• tests/unit/checkpointing_nnx_load_test.py::TestShapeDtypeStructPath — a surviving ShapeDtypeStruct raises naming its path and shape; concrete arrays pass.

Checklist

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[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 3 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/maxtext/common/checkpointing.py	50.00%	3 Missing ⚠️

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