Arrow parse

[Lan2u]

Fixes #1032
Fixes a bug in arrow function parsing which prevented the assignment of arrow functions with a single argument using parentheses (e.g. let foo = (a) => a )

Arrow functions with > 1 argument or arrow functions that don't use parentheses already parse correctly

[github-actions]

Test262 conformance changes:

Test result	master count	PR count	difference
Total	78,497	78,497	0
Passed	24,548	24,557	+9
Ignored	15,585	15,585	0
Failed	38,364	38,355	-9
Panics	28	28	0
Conformance	31.27	31.28	+0.01%

[github-actions]

Benchmark for 033786f

Click to view benchmark

Test	PR Benchmark	Master Benchmark	%
Arithmetic operations (Execution)	315.8±20.33ns	297.9±19.15ns	+6.01%
Arithmetic operations (Full)	190.7±12.91µs	210.0±8.89µs	-9.19%
Array access (Execution)	5.4±0.30µs	5.3±0.33µs	+1.89%
Array access (Full)	208.3±14.18µs	211.8±14.63µs	-1.65%
Array creation (Execution)	2.8±0.11ms	2.5±0.16ms	+12.00%
Array creation (Full)	2.8±0.15ms	2.7±0.15ms	+3.70%
Array pop (Execution)	952.1±36.77µs	805.0±52.18µs	+18.27%
Array pop (Full)	1206.7±72.91µs	1171.3±73.16µs	+3.02%
Boolean Object Access (Execution)	4.3±0.21µs	4.2±0.27µs	+2.38%
Boolean Object Access (Full)	199.1±12.65µs	204.1±12.37µs	-2.45%
Clean js (Execution)	595.8±31.53µs	563.7±33.70µs	+5.69%
Clean js (Full)	863.2±47.31µs	843.9±39.20µs	+2.29%
Clean js (Parser)	116.7±29.77µs	29.0±1.82µs	+302.41%
Create Realm	408.2±27.85ns	429.2±32.37ns	-4.89%
Dynamic Object Property Access (Execution)	4.7±0.34µs	4.2±0.26µs	+11.90%
Dynamic Object Property Access (Full)	212.8±13.05µs	199.3±12.88µs	+6.77%
Expression (Parser)	6.0±0.39µs	5.9±0.41µs	+1.69%
Fibonacci (Execution)	758.2±40.43µs	711.7±44.59µs	+6.53%
Fibonacci (Full)	941.1±49.16µs	930.6±49.88µs	+1.13%
For loop (Execution)	18.8±1.31µs	19.3±1.24µs	-2.59%
For loop (Full)	258.8±6.92µs	222.5±13.75µs	+16.31%
For loop (Parser)	14.4±0.76µs	14.4±0.90µs	0.00%
Goal Symbols (Parser)	10.3±0.52µs	9.5±0.62µs	+8.42%
Hello World (Parser)	2.7±0.16µs	2.5±0.14µs	+8.00%
Long file (Parser)	674.3±42.28ns	696.9±40.48ns	-3.24%
Mini js (Execution)	546.1±24.85µs	513.4±33.37µs	+6.37%
Mini js (Full)	833.0±49.64µs	750.2±41.52µs	+11.04%
Mini js (Parser)	92.6±30.14µs	25.6±1.41µs	+261.72%
Number Object Access (Execution)	3.4±0.20µs	3.4±0.21µs	0.00%
Number Object Access (Full)	195.0±11.96µs	207.0±12.82µs	-5.80%
Object Creation (Execution)	4.2±0.10µs	3.6±0.21µs	+16.67%
Object Creation (Full)	207.7±13.75µs	201.8±11.81µs	+2.92%
RegExp (Execution)	8.9±0.34µs	8.0±0.53µs	+11.25%
RegExp (Full)	212.1±13.78µs	219.0±13.61µs	-3.15%
RegExp Literal (Execution)	10.1±0.45µs	9.1±0.61µs	+10.99%
RegExp Literal (Full)	220.3±18.60µs	215.8±13.46µs	+2.09%
RegExp Literal Creation (Execution)	9.1±0.33µs	7.8±0.46µs	+16.67%
RegExp Literal Creation (Full)	210.7±13.28µs	211.3±12.02µs	-0.28%
Static Object Property Access (Execution)	4.5±0.09µs	3.9±0.26µs	+15.38%
Static Object Property Access (Full)	208.0±12.77µs	215.2±14.86µs	-3.35%
String Object Access (Execution)	5.9±0.29µs	6.3±0.33µs	-6.35%
String Object Access (Full)	205.0±12.67µs	221.2±10.72µs	-7.32%
String comparison (Execution)	5.9±0.29µs	5.4±0.31µs	+9.26%
String comparison (Full)	221.7±12.69µs	214.1±12.99µs	+3.55%
String concatenation (Execution)	4.9±0.17µs	4.3±0.25µs	+13.95%
String concatenation (Full)	197.6±12.24µs	211.7±12.98µs	-6.66%
String copy (Execution)	3.5±0.20µs	3.3±0.22µs	+6.06%
String copy (Full)	193.5±11.57µs	198.6±11.55µs	-2.57%
Symbols (Execution)	2.8±0.17µs	2.8±0.17µs	0.00%
Symbols (Full)	206.4±9.29µs	191.2±12.23µs	+7.95%

[Razican]

Looks very good, thanks! Could we add also a test to check for 3 arguments? Just in case.

Also a couple of prints left.

[codecov]

Codecov Report

Merging #1051 (c3efb60) into master (c083c85) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #1051   +/-   ##
=======================================
  Coverage   58.31%   58.31%           
=======================================
  Files         172      172           
  Lines       12007    12007           
=======================================
  Hits         7002     7002           
  Misses       5005     5005           

Impacted Files	Coverage Δ
boa/src/syntax/parser/cursor/buffered_lexer/mod.rs	85.91% <ø> (ø)
...tax/parser/expression/assignment/arrow_function.rs	89.18% <ø> (ø)
boa/src/syntax/parser/expression/assignment/mod.rs	50.00% <100.00%> (ø)

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[github-actions]

Benchmark for b4c6ed8

Click to view benchmark

Test	PR Benchmark	Master Benchmark	%
Arithmetic operations (Execution)	349.9±5.19ns	346.5±5.14ns	+0.98%
Arithmetic operations (Full)	223.2±4.24µs	226.4±3.16µs	-1.41%
Array access (Execution)	6.1±0.10µs	6.1±0.11µs	0.00%
Array access (Full)	246.5±5.79µs	243.6±2.90µs	+1.19%
Array creation (Execution)	2.9±0.04ms	2.9±0.03ms	0.00%
Array creation (Full)	3.2±0.08ms	3.2±0.03ms	0.00%
Array pop (Execution)	947.8±16.46µs	925.5±11.14µs	+2.41%
Array pop (Full)	1369.0±16.37µs	1369.3±16.71µs	-0.02%
Boolean Object Access (Execution)	4.9±0.11µs	4.7±0.08µs	+4.26%
Boolean Object Access (Full)	235.0±3.39µs	236.7±3.35µs	-0.72%
Clean js (Execution)	657.1±10.75µs	658.8±9.24µs	-0.26%
Clean js (Full)	943.3±21.59µs	932.6±14.36µs	+1.15%
Clean js (Parser)	33.4±0.45µs	33.3±0.47µs	+0.30%
Create Realm	473.8±5.51ns	479.6±8.90ns	-1.21%
Dynamic Object Property Access (Execution)	4.9±0.07µs	5.0±0.07µs	-2.00%
Dynamic Object Property Access (Full)	240.0±4.06µs	238.4±2.45µs	+0.67%
Expression (Parser)	6.5±0.09µs	6.6±0.13µs	-1.52%
Fibonacci (Execution)	829.6±9.88µs	824.4±10.79µs	+0.63%
Fibonacci (Full)	1079.4±16.63µs	1078.6±16.34µs	+0.07%
For loop (Execution)	22.3±0.36µs	22.1±0.70µs	+0.90%
For loop (Full)	261.2±3.93µs	262.4±3.42µs	-0.46%
For loop (Parser)	16.8±0.26µs	16.7±0.28µs	+0.60%
Goal Symbols (Parser)	11.1±0.15µs	11.0±0.16µs	+0.91%
Hello World (Parser)	3.0±0.04µs	2.9±0.05µs	+3.45%
Long file (Parser)	780.1±9.25ns	765.1±9.31ns	+1.96%
Mini js (Execution)	593.4±11.16µs	587.8±9.18µs	+0.95%
Mini js (Full)	848.3±11.64µs	856.7±12.94µs	-0.98%
Mini js (Parser)	29.6±0.61µs	29.3±0.41µs	+1.02%
Number Object Access (Execution)	3.8±0.07µs	3.8±0.08µs	0.00%
Number Object Access (Full)	237.0±4.29µs	235.0±3.76µs	+0.85%
Object Creation (Execution)	4.2±0.06µs	4.2±0.05µs	0.00%
Object Creation (Full)	235.4±3.67µs	236.9±4.73µs	-0.63%
RegExp (Execution)	9.3±0.13µs	9.2±0.13µs	+1.09%
RegExp (Full)	249.2±3.93µs	247.7±4.26µs	+0.61%
RegExp Literal (Execution)	10.7±0.31µs	10.5±0.17µs	+1.90%
RegExp Literal (Full)	245.7±3.71µs	244.5±3.40µs	+0.49%
RegExp Literal Creation (Execution)	9.3±0.18µs	9.2±0.11µs	+1.09%
RegExp Literal Creation (Full)	239.8±3.46µs	239.9±2.94µs	-0.04%
Static Object Property Access (Execution)	4.5±0.06µs	4.5±0.08µs	0.00%
Static Object Property Access (Full)	236.0±3.23µs	237.9±2.96µs	-0.80%
String Object Access (Execution)	6.7±0.10µs	6.6±0.07µs	+1.52%
String Object Access (Full)	238.9±3.86µs	242.1±4.03µs	-1.32%
String comparison (Execution)	6.3±0.08µs	6.3±0.12µs	0.00%
String comparison (Full)	243.4±4.52µs	244.8±5.51µs	-0.57%
String concatenation (Execution)	5.1±0.09µs	5.0±0.09µs	+2.00%
String concatenation (Full)	235.5±3.63µs	234.1±2.95µs	+0.60%
String copy (Execution)	3.9±0.06µs	3.8±0.07µs	+2.63%
String copy (Full)	228.7±3.34µs	230.4±3.10µs	-0.74%
Symbols (Execution)	3.3±0.08µs	3.2±0.05µs	+3.12%
Symbols (Full)	226.0±3.36µs	225.8±3.78µs	+0.09%