## Motivation and context
The TVMScript parser already tracks Python AST locations for
diagnostics, but TIRx statements and expression results emitted through
`IRBuilder` did not retain those locations. After parsing, a direct
intrinsic call, an inlined helper body, or a `TilePrimitiveCall`
therefore could not be traced back to the source range that produced it.
Inline expansion also needs more than a single flat location. The
generated IR should retain both the caller location and the
helper-definition location, while ordinary nested AST evaluation within
one source should not accumulate redundant enclosing spans.
## Changes
- Add an active source-span stack to `IRBuilder`, with scoped push/pop
support.
- Make the parser activate the current AST source range while visiting
statements and evaluating expressions.
- Attach the active span to emitted TIRx statements and to expression
results that do not already carry an explicit span.
- Normalize nested spans from the same source to the innermost relevant
range.
- Preserve cross-source inline expansion history as a `SequentialSpan`,
ordered from the call site to the expanded definition.
- Reuse the same source-coordinate calculation for diagnostics and IR
spans so their line and column conventions remain consistent.
Source spans remain diagnostic metadata: functions parsed from different
source locations keep the same structural hash and remain structurally
equal.
## Testing
- Verify exact parser source coordinates against diagnostic coordinates.
- Verify spans on direct intrinsic calls and `TilePrimitiveCall` nodes.
- Verify that inline expansion produces a `SequentialSpan` containing
caller and callee ranges.
- Verify direct `IRBuilder.with_source_span` behavior.
- Verify that source spans do not affect structural identity.
- Run changed-files pre-commit checks, including clang-format.
Focused result: 9 tests passed.
Hongyi Jin
ae99c3fd92