Implement Param add/mul as proper methods

[Cryoris]

Summary

This commit implements the methods Param::add(_f64) and Param::mul(_f64), which previously existed as standalone functions in various places. This ensures we have a single place for these methods which is easily discoverable and cleans up the code.

Details and comments

This came up when implementing the C API for Param in #14837.

This also removes the single call to clone_param(&Param) -> Param which is already covered by Param::clone.

[qiskit-bot]

One or more of the following people are relevant to this code:

• @Qiskit/terra-core

[jakelishman]

If we're going to raise these to Param, they need to be given names that clearly indicate at the call site that they do not actually support all Param instances, or we're just asking to make mistakes.

[jakelishman]

This is not unreachable. Unreachable isn't for marking "I don't want you to get here", it's for marking "this is literally impossible but the compiler can't reason about it".

[Cryoris]

yep, that's an oversight from copying it over 😅

[Cryoris]

A nicer way would be to have a proper error here -- we should also propagate the name-conflict error that we currently just .expect()

[jakelishman]

The panic is suitable if it could only have been caused by an internal logic error within the Rust code, but yeah, a non-aborting error for the name conflict would be nicer.

[coveralls]

Pull Request Test Coverage Report for Build 17910214757

Details

• 104 of 120 (86.67%) changed or added relevant lines in 9 files are covered.
• 23 unchanged lines in 5 files lost coverage.
• Overall coverage increased (+0.006%) to 88.283%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
crates/circuit/src/operations.rs	85	101	84.16%

Files with Coverage Reduction	New Missed Lines	%
crates/circuit/src/parameter/parameter_expression.rs	1	82.79%
crates/transpiler/src/passes/unitary_synthesis.rs	1	92.4%
crates/circuit/src/parameter/symbol_expr.rs	4	72.74%
crates/qasm2/src/lex.rs	5	91.75%
crates/qasm2/src/parse.rs	12	97.09%

Totals
Change from base Build 17859742834:	0.006%
Covered Lines:	92683
Relevant Lines:	104984

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💛 - Coveralls

[jakelishman]

The conflicts here are probably mostly related to the move to Rust 2024, especially the format update.

Do you want to include all the mathematical operations on numeric-like arguments that we identified in #14837, so that we can (in a follow up PR) then migrate the C API code of Param to use them?

[Cryoris]

Yeah we can already include them in this PR 👍🏻 though if we move them here, then we should maybe directly update the QkParam class to use them, right?

[jakelishman]

I don't mind if you want to do it in this PR, or move them over in a follow-up.