Improve the AST visitor further

[turbolent]

Description

Remove the combined Visitor and introduce separate Accept* functions for declarations, statements, and expressions. This allows implementations, like the checker and interpreter, to specify different return values. For example, the interpreter returns Values for expressions, but StatementResult for statements.

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• Targeted PR against master branch
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work
• Code follows the standards mentioned here
• Updated relevant documentation
• Re-reviewed Files changed in the Github PR explorer
• Added appropriate labels

[codecov]

Codecov Report

Merging #1919 (aa41abb) into master (c9a3614) will increase coverage by 0.09%.
The diff coverage is 76.51%.

@@            Coverage Diff             @@
##           master    #1919      +/-   ##
==========================================
+ Coverage   77.62%   77.72%   +0.09%     
==========================================
  Files         303      303              
  Lines       62081    62009      -72     
==========================================
+ Hits        48190    48194       +4     
+ Misses      12171    12096      -75     
+ Partials     1720     1719       -1     

Flag	Coverage Δ
unittests	77.72% <76.51%> (+0.09%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
runtime/ast/block.go	98.23% <ø> (+1.10%)	⬆️
runtime/ast/composite.go	86.64% <ø> (+1.07%)	⬆️
runtime/ast/expression.go	91.01% <ø> (+2.54%)	⬆️
runtime/ast/function_declaration.go	81.35% <ø> (+1.02%)	⬆️
runtime/ast/import.go	91.11% <ø> (-0.20%)	⬇️
runtime/ast/interface.go	100.00% <ø> (ø)
runtime/ast/pragma.go	78.37% <ø> (+4.01%)	⬆️
runtime/ast/program.go	69.23% <ø> (-0.59%)	⬇️
runtime/ast/statement.go	92.10% <ø> (+3.82%)	⬆️
runtime/ast/transaction_declaration.go	82.65% <ø> (+1.65%)	⬆️
... and 52 more

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[github-actions]

Cadence Benchstat comparison

This branch with compared with the base branch onflow:master commit 599dda3
The command for i in {1..N}; do go test ./... -run=XXX -bench=. -benchmem -shuffle=on; done was used.
Bench tests were run a total of 7 times on each branch.

Collapsed results for better readability

	old.txt	new.txt
	time/op		delta
CheckContractInterfaceFungibleTokenConformance-2	211µs ± 9%	182µs ± 4%	−13.95%	(p=0.001 n=7+6)
ContractInterfaceFungibleToken-2	55.6µs ±12%	49.5µs ± 7%	−10.91%	(p=0.002 n=7+7)
InterpretRecursionFib-2	3.54ms ± 6%	3.08ms ± 6%	−13.00%	(p=0.001 n=7+7)
NewInterpreter/new_interpreter-2	1.45µs ± 4%	1.39µs ± 9%	~	(p=0.097 n=7+7)
NewInterpreter/new_sub-interpreter-2	839ns ± 2%	799ns ± 8%	~	(p=0.101 n=6+7)
ParseArray-2	10.9ms ± 2%	10.3ms ± 5%	−5.46%	(p=0.002 n=7+6)
ParseDeploy/byte_array-2	16.9ms ± 7%	15.8ms ± 5%	−6.82%	(p=0.005 n=7+6)
ParseDeploy/decode_hex-2	1.49ms ± 3%	1.41ms ± 3%	−5.14%	(p=0.001 n=7+6)
ParseFungibleToken/With_memory_metering-2	277µs ± 4%	272µs ± 9%	~	(p=0.710 n=7+7)
ParseFungibleToken/Without_memory_metering-2	211µs ± 7%	197µs ± 4%	−6.73%	(p=0.014 n=7+6)
ParseInfix-2	9.41µs ± 3%	9.11µs ±11%	~	(p=0.128 n=7+7)
QualifiedIdentifierCreation/One_level-2	3.48ns ± 3%	3.27ns ± 2%	−6.03%	(p=0.001 n=7+6)
QualifiedIdentifierCreation/Three_levels-2	185ns ± 5%	174ns ± 7%	−5.89%	(p=0.017 n=7+7)
RuntimeFungibleTokenTransfer-2	876µs ±23%	787µs ±25%	~	(p=0.073 n=7+7)
RuntimeResourceDictionaryValues-2	6.71ms ± 6%	6.13ms ± 5%	−8.68%	(p=0.002 n=7+6)
RuntimeScriptNoop-2	25.5µs ±47%	22.2µs ±54%	~	(p=0.165 n=7+7)
ValueIsSubtypeOfSemaType-2	118ns ± 6%	112ns ± 1%	−4.99%	(p=0.018 n=7+5)
	alloc/op		delta
CheckContractInterfaceFungibleTokenConformance-2	61.5kB ± 0%	61.5kB ± 0%	−0.01%	(p=0.001 n=7+7)
ContractInterfaceFungibleToken-2	23.9kB ± 0%	23.9kB ± 0%	~	(all equal)
InterpretRecursionFib-2	1.23MB ± 0%	1.23MB ± 0%	−0.00%	(p=0.003 n=7+6)
NewInterpreter/new_interpreter-2	848B ± 0%	848B ± 0%	~	(all equal)
NewInterpreter/new_sub-interpreter-2	264B ± 0%	264B ± 0%	~	(all equal)
ParseArray-2	2.81MB ± 2%	2.79MB ± 3%	~	(p=0.334 n=7+7)
ParseDeploy/byte_array-2	4.47MB ± 3%	4.47MB ± 3%	~	(p=0.710 n=7+7)
ParseDeploy/decode_hex-2	214kB ± 0%	214kB ± 0%	~	(p=0.639 n=7+6)
ParseFungibleToken/With_memory_metering-2	36.3kB ± 0%	36.3kB ± 0%	~	(p=0.538 n=6+7)
ParseFungibleToken/Without_memory_metering-2	36.3kB ± 0%	36.3kB ± 0%	~	(p=0.559 n=7+7)
ParseInfix-2	2.17kB ± 0%	2.17kB ± 0%	~	(p=1.000 n=7+7)
QualifiedIdentifierCreation/One_level-2	0.00B	0.00B	~	(all equal)
QualifiedIdentifierCreation/Three_levels-2	64.0B ± 0%	64.0B ± 0%	~	(all equal)
RuntimeFungibleTokenTransfer-2	111kB ± 1%	111kB ± 1%	~	(p=0.620 n=7+7)
RuntimeResourceDictionaryValues-2	2.27MB ± 0%	2.27MB ± 0%	~	(p=0.805 n=7+7)
RuntimeScriptNoop-2	8.64kB ± 1%	8.63kB ± 1%	~	(p=0.902 n=7+7)
ValueIsSubtypeOfSemaType-2	48.0B ± 0%	48.0B ± 0%	~	(all equal)
	allocs/op		delta
CheckContractInterfaceFungibleTokenConformance-2	1.03k ± 0%	1.03k ± 0%	~	(all equal)
ContractInterfaceFungibleToken-2	426 ± 0%	426 ± 0%	~	(all equal)
InterpretRecursionFib-2	22.5k ± 0%	22.5k ± 0%	~	(all equal)
NewInterpreter/new_interpreter-2	14.0 ± 0%	14.0 ± 0%	~	(all equal)
NewInterpreter/new_sub-interpreter-2	5.00 ± 0%	5.00 ± 0%	~	(all equal)
ParseArray-2	70.0k ± 0%	70.0k ± 0%	~	(p=1.000 n=7+7)
ParseDeploy/byte_array-2	105k ± 0%	105k ± 0%	~	(p=1.000 n=7+7)
ParseDeploy/decode_hex-2	77.0 ± 0%	77.0 ± 0%	~	(all equal)
ParseFungibleToken/With_memory_metering-2	1.06k ± 0%	1.06k ± 0%	~	(all equal)
ParseFungibleToken/Without_memory_metering-2	1.06k ± 0%	1.06k ± 0%	~	(all equal)
ParseInfix-2	66.0 ± 0%	66.0 ± 0%	~	(all equal)
QualifiedIdentifierCreation/One_level-2	0.00	0.00	~	(all equal)
QualifiedIdentifierCreation/Three_levels-2	2.00 ± 0%	2.00 ± 0%	~	(all equal)
RuntimeFungibleTokenTransfer-2	2.20k ± 0%	2.20k ± 0%	~	(p=1.000 n=7+7)
RuntimeResourceDictionaryValues-2	36.9k ± 0%	36.9k ± 0%	~	(p=1.000 n=7+6)
RuntimeScriptNoop-2	143 ± 0%	143 ± 0%	~	(all equal)
ValueIsSubtypeOfSemaType-2	1.00 ± 0%	1.00 ± 0%	~	(all equal)

[dsainati1]

Nice