Dereferencing as reassignment target

[ironcev]

Description

This PR implements dereferencing in reassignment targets, as defined in references. The overall effort related to references is tracked in #5063.

Up to now, it was only possible to read the values references refer to. This PR allows values to be written over &mut references. In other words, any *<expression that results in &mut>is now an l-values and can be used in left-hand sides (LHS) of assignments. In most of the cases, the <expression> will very likely be just a reference variable, but any expression that results in &mut is allowed and supported. E.g.;

*mut_ref_to_u64 = 42;

*if condition { &mut x } else { &mut y } = 42;

*max_mut(&mut x, &mut y) = 42;

Additionally, the PR:

• fixes Internal compiler error when using generic items in array indexing in reassignments #5736 by properly replacing decls in reassignment LHSs.
• fixes Internal compiler error when using generic types in array indexing in reassignments #5737 by properly substituting types in reassignment LHSs.
• fixes Wrong "This declaration is never used." warning when variables are used only in reassignment LHS in index expressions  #5920 by properly connecting expressions in array indices to the DCA graph.
• fixes Type of the array index not type-checked in reassignment LHS #5922 by type-cheking the array indices in reassignment LHSs and forcing them to be u64.
• improves misplaced and misleading error messages when assigning to constants and other items (see demo below).
• improves error message when assigning to immutable variables by pointing to variable declaration.
• improves error message when expression cannot be assigned to by pointing to the problematic part of the expression. Since Sway is more restrictive here then Rust, the restrictions, without being explained, could cause confusion. That's why special attention was given to point to the exact issue and explain what is actually supported in Sway (see demo below).
• reduces number of expected warnings in references E2E tests that were previously set high because of DCA issues that are fixed in the meantime.

The PR also brings additional analysis and checks to IR optimizations. Among other things, it explicitly points out the cases in which a potential usage of a symbol cannot be deterministically confirmed or denied. In this PR properly reacting for such cases is done in some optimizations. Rolling it out fully will be done in a follow up PR #5924. More advanced escape analysis will be done later on, as a part of allocating values on the heap in case of referencing.

This PR implements only dereferencing in LHS. Support for referenced elements in the element based access (without dereferencing) will be done in a separate step as an ongoing work on implementing #5063.

Closes #5736, #5737, #5920, #5922.

Demo

Before:

After:

Expression cannot be assigned to:

Checklist

• I have linked to any relevant issues.
• I have commented my code, particularly in hard-to-understand areas.
• I have updated the documentation where relevant (API docs, the reference, and the Sway book).
  • If my change requires substantial documentation changes, I have requested support from the DevRel team
• I have added tests that prove my fix is effective or that my feature works.
• I have added (or requested a maintainer to add) the necessary Breaking* or New Feature labels where relevant.
• I have done my best to ensure that my PR adheres to the Fuel Labs Code Review Standards.
• I have requested a review from the relevant team or maintainers.

[github-actions]

Benchmark for fd7f2c7

Click to view benchmark

Test	Base	PR	%
code_action	5.5±0.11ms	5.6±0.12ms	+1.82%
code_lens	329.6±3.90ns	288.1±11.22ns	-12.59%
compile	6.2±0.09s	6.1±0.05s	-1.61%
completion	5.0±0.08ms	5.0±0.14ms	0.00%
did_change_with_caching	6.5±0.08s	6.1±0.07s	-6.15%
document_symbol	1080.0±38.74µs	967.1±28.00µs	-10.45%
format	74.1±0.91ms	89.3±1.07ms	+20.51%
goto_definition	362.7±4.74µs	353.0±3.80µs	-2.67%
highlight	9.0±0.04ms	9.0±0.19ms	0.00%
hover	598.5±6.34µs	598.0±19.65µs	-0.08%
idents_at_position	122.7±0.57µs	123.5±2.60µs	+0.65%
inlay_hints	667.5±23.68µs	662.4±27.65µs	-0.76%
on_enter	495.6±6.85ns	483.1±11.80ns	-2.52%
parent_decl_at_position	3.7±0.03ms	3.7±0.18ms	0.00%
prepare_rename	359.5±5.72µs	358.4±24.16µs	-0.31%
rename	9.7±0.19ms	9.6±0.14ms	-1.03%
semantic_tokens	1035.6±15.45µs	1029.0±15.80µs	-0.64%
token_at_position	354.3±3.06µs	355.6±7.33µs	+0.37%
tokens_at_position	3.7±0.02ms	3.7±0.06ms	0.00%
tokens_for_file	416.9±1.87µs	421.1±1.78µs	+1.01%
traverse	52.5±1.54ms	51.0±2.46ms	-2.86%

[github-actions]

Benchmark for 66646f7

Click to view benchmark

Test	Base	PR	%
code_action	5.6±0.07ms	5.5±0.02ms	-1.79%
code_lens	334.9±8.37ns	287.0±21.85ns	-14.30%
compile	6.1±0.08s	6.1±0.03s	0.00%
completion	5.0±0.09ms	4.9±0.07ms	-2.00%
did_change_with_caching	6.0±0.05s	6.1±0.04s	+1.67%
document_symbol	989.3±39.15µs	1050.8±21.43µs	+6.22%
format	71.6±1.10ms	86.4±0.89ms	+20.67%
goto_definition	361.7±6.25µs	384.3±3.50µs	+6.25%
highlight	9.0±0.09ms	9.2±0.10ms	+2.22%
hover	608.2±9.06µs	601.4±7.24µs	-1.12%
idents_at_position	122.9±0.60µs	123.3±1.22µs	+0.33%
inlay_hints	662.0±12.58µs	687.5±9.54µs	+3.85%
on_enter	496.8±15.31ns	479.8±12.94ns	-3.42%
parent_decl_at_position	3.7±0.02ms	3.7±0.05ms	0.00%
prepare_rename	365.3±5.97µs	356.6±17.05µs	-2.38%
rename	9.8±0.13ms	9.6±0.01ms	-2.04%
semantic_tokens	1007.5±10.53µs	1033.0±25.52µs	+2.53%
token_at_position	360.4±9.09µs	363.8±3.27µs	+0.94%
tokens_at_position	3.7±0.03ms	3.7±0.03ms	0.00%
tokens_for_file	417.9±2.20µs	433.5±2.80µs	+3.73%
traverse	49.3±1.49ms	49.2±1.14ms	-0.20%

[github-actions]

Benchmark for d32779f

Click to view benchmark

Test	Base	PR	%
code_action	5.5±0.02ms	5.5±0.04ms	0.00%
code_lens	327.3±10.42ns	289.9±4.96ns	-11.43%
compile	6.1±0.07s	6.1±0.08s	0.00%
completion	4.9±0.06ms	5.0±0.15ms	+2.04%
did_change_with_caching	6.1±0.08s	6.0±0.06s	-1.64%
document_symbol	1054.4±27.95µs	929.8±14.51µs	-11.82%
format	70.1±0.89ms	87.1±0.92ms	+24.25%
goto_definition	363.1±4.77µs	366.8±7.32µs	+1.02%
highlight	9.1±0.14ms	8.9±0.03ms	-2.20%
hover	597.5±14.17µs	604.2±20.93µs	+1.12%
idents_at_position	122.4±0.24µs	123.2±1.62µs	+0.65%
inlay_hints	666.4±22.23µs	662.3±27.24µs	-0.62%
on_enter	489.4±11.74ns	482.0±13.08ns	-1.51%
parent_decl_at_position	3.7±0.02ms	3.7±0.06ms	0.00%
prepare_rename	365.9±8.17µs	361.8±7.04µs	-1.12%
rename	9.8±0.14ms	9.5±0.16ms	-3.06%
semantic_tokens	1096.3±11.56µs	1039.3±14.25µs	-5.20%
token_at_position	356.8±1.80µs	356.0±13.21µs	-0.22%
tokens_at_position	3.7±0.04ms	3.8±0.30ms	+2.70%
tokens_for_file	419.1±3.76µs	429.0±2.54µs	+2.36%
traverse	51.4±1.78ms	51.3±2.09ms	-0.19%

[github-actions]

Benchmark for 3d17592

Click to view benchmark

Test	Base	PR	%
code_action	5.6±0.07ms	5.6±0.12ms	0.00%
code_lens	324.3±4.60ns	288.7±9.70ns	-10.98%
compile	6.2±0.06s	6.2±0.07s	0.00%
completion	5.0±0.08ms	5.1±0.33ms	+2.00%
did_change_with_caching	6.2±0.03s	6.2±0.06s	0.00%
document_symbol	994.0±34.71µs	934.7±21.83µs	-5.97%
format	72.9±1.10ms	90.2±1.36ms	+23.73%
goto_definition	364.1±2.67µs	368.0±8.50µs	+1.07%
highlight	9.1±0.07ms	9.0±0.24ms	-1.10%
hover	642.4±11.14µs	603.5±23.91µs	-6.06%
idents_at_position	122.5±0.59µs	123.5±2.06µs	+0.82%
inlay_hints	664.6±19.77µs	668.3±7.61µs	+0.56%
on_enter	493.0±13.36ns	482.2±15.95ns	-2.19%
parent_decl_at_position	3.7±0.04ms	3.7±0.10ms	0.00%
prepare_rename	356.1±4.05µs	363.3±6.39µs	+2.02%
rename	9.9±0.25ms	9.8±0.22ms	-1.01%
semantic_tokens	1023.6±18.79µs	1030.7±11.58µs	+0.69%
token_at_position	360.4±2.70µs	359.7±3.33µs	-0.19%
tokens_at_position	3.7±0.03ms	3.7±0.09ms	0.00%
tokens_for_file	462.5±4.40µs	429.4±1.42µs	-7.16%
traverse	51.0±1.46ms	51.5±1.22ms	+0.98%

[github-actions]

Benchmark for 2722d9b

Click to view benchmark

Test	Base	PR	%
code_action	5.6±0.09ms	5.5±0.12ms	-1.79%
code_lens	342.1±5.61ns	284.2±6.72ns	-16.92%
compile	6.1±0.05s	6.1±0.10s	0.00%
completion	5.0±0.05ms	4.9±0.11ms	-2.00%
did_change_with_caching	6.2±0.07s	6.2±0.07s	0.00%
document_symbol	937.8±19.60µs	984.1±34.75µs	+4.94%
format	73.0±7.59ms	87.6±1.05ms	+20.00%
goto_definition	364.1±4.79µs	361.6±8.86µs	-0.69%
highlight	9.2±0.11ms	9.0±0.16ms	-2.17%
hover	616.9±13.16µs	595.9±8.78µs	-3.40%
idents_at_position	122.9±2.46µs	121.9±0.66µs	-0.81%
inlay_hints	672.4±6.60µs	661.1±12.04µs	-1.68%
on_enter	465.5±23.65ns	478.9±15.16ns	+2.88%
parent_decl_at_position	3.7±0.11ms	3.7±0.03ms	0.00%
prepare_rename	359.6±2.92µs	362.8±15.48µs	+0.89%
rename	9.8±0.15ms	9.6±0.41ms	-2.04%
semantic_tokens	1050.0±16.64µs	1045.0±18.71µs	-0.48%
token_at_position	360.0±10.27µs	354.3±4.25µs	-1.58%
tokens_at_position	3.7±0.08ms	3.7±0.05ms	0.00%
tokens_for_file	422.9±7.55µs	423.1±3.49µs	+0.05%
traverse	51.7±2.21ms	49.8±2.15ms	-3.68%

[github-actions]

Benchmark for b76f699

Click to view benchmark

Test	Base	PR	%
code_action	5.6±0.13ms	5.5±0.11ms	-1.79%
code_lens	324.1±10.40ns	285.8±9.24ns	-11.82%
compile	6.1±0.06s	6.2±0.06s	+1.64%
completion	4.9±0.02ms	4.9±0.01ms	0.00%
did_change_with_caching	6.0±0.06s	6.2±0.08s	+3.33%
document_symbol	1013.0±32.81µs	942.0±17.28µs	-7.01%
format	70.7±0.64ms	86.0±1.34ms	+21.64%
goto_definition	366.3±5.48µs	365.1±5.96µs	-0.33%
highlight	9.0±0.02ms	9.0±0.09ms	0.00%
hover	618.1±25.50µs	601.1±18.78µs	-2.75%
idents_at_position	123.3±0.42µs	122.3±1.42µs	-0.81%
inlay_hints	672.5±10.46µs	678.3±17.47µs	+0.86%
on_enter	507.7±9.11ns	484.1±20.58ns	-4.65%
parent_decl_at_position	3.7±0.03ms	3.7±0.03ms	0.00%
prepare_rename	359.8±4.36µs	354.8±7.33µs	-1.39%
rename	9.6±0.31ms	9.5±0.14ms	-1.04%
semantic_tokens	1050.7±13.51µs	1072.7±15.26µs	+2.09%
token_at_position	356.5±2.42µs	352.9±3.52µs	-1.01%
tokens_at_position	3.7±0.02ms	3.7±0.03ms	0.00%
tokens_for_file	424.3±6.56µs	422.1±1.40µs	-0.52%
traverse	50.2±1.68ms	49.4±1.56ms	-1.59%

[jjcnn]

I have not yet had a chance to look through your tests, so I'm holding off on final approval. I've looked through all the code, though, and except for a couple of minor issues here and there everything looks sound.

[jjcnn]

One small but (I think) important mistake in one of the tests, but other than that the tests look fine.

[github-actions]

Benchmark for 4215a05

Click to view benchmark

Test	Base	PR	%
code_action	5.6±0.10ms	5.4±0.03ms	-3.57%
code_lens	359.8±29.44ns	289.3±28.37ns	-19.59%
compile	6.3±0.04s	6.3±0.04s	0.00%
completion	5.0±0.09ms	4.9±0.20ms	-2.00%
did_change_with_caching	6.3±0.07s	6.3±0.06s	0.00%
document_symbol	1010.0±51.15µs	955.5±32.31µs	-5.40%
format	72.7±1.71ms	86.9±1.74ms	+19.53%
goto_definition	361.0±6.74µs	370.9±7.37µs	+2.74%
highlight	9.0±0.15ms	9.0±0.23ms	0.00%
hover	605.7±9.27µs	603.8±17.83µs	-0.31%
idents_at_position	123.4±0.35µs	123.0±1.74µs	-0.32%
inlay_hints	666.9±16.86µs	665.8±21.00µs	-0.16%
on_enter	490.6±17.45ns	479.8±20.92ns	-2.20%
parent_decl_at_position	3.7±0.02ms	3.7±0.05ms	0.00%
prepare_rename	355.6±8.34µs	365.7±12.86µs	+2.84%
rename	9.6±0.08ms	9.7±0.86ms	+1.04%
semantic_tokens	1026.1±7.24µs	1046.3±13.09µs	+1.97%
token_at_position	379.0±5.96µs	352.4±2.04µs	-7.02%
tokens_at_position	3.7±0.04ms	3.7±0.06ms	0.00%
tokens_for_file	463.8±2.46µs	424.3±2.55µs	-8.52%
traverse	51.9±2.04ms	51.5±1.33ms	-0.77%

[jjcnn]

LGTM