Implement implicit_assignment_linter()

[IndrajeetPatil]

Closes #1777

---

library(lintr)

# will produce lints
lint(
  text = "if (x <- 1L) TRUE",
  linters = implicit_assignment_linter()
)
#> <text>:1:7: warning: [implicit_assignment_linter] Avoid implicit assignments in function calls. For example, instead of `if (x <- 1L) { ... }`, write `x <- 1L; if (x) { ... }`.
#> if (x <- 1L) TRUE
#>       ^~

lint(
  text = "mean(x <- 1:4)",
  linters = implicit_assignment_linter()
)
#> <text>:1:8: warning: [implicit_assignment_linter] Avoid implicit assignments in function calls. For example, instead of `if (x <- 1L) { ... }`, write `x <- 1L; if (x) { ... }`.
#> mean(x <- 1:4)
#>        ^~

# okay
writeLines("x <- 1L\nif (x) TRUE")
#> x <- 1L
#> if (x) TRUE
lint(
  text = "x <- 1L\nif (x) TRUE",
  linters = implicit_assignment_linter()
)

writeLines("x <- 1:4\nmean(x)")
#> x <- 1:4
#> mean(x)
lint(
  text = "x <- 1:4\nmean(x)",
  linters = implicit_assignment_linter()
)

^{Created on 2022-12-08 with reprex v2.0.2}

[codecov-commenter]

Codecov Report

Merging #1814 (2cc6460) into main (77baa3e) will decrease coverage by 0.04%.
The diff coverage is 89.89%.

❗ Current head 2cc6460 differs from pull request most recent head 3469d9d. Consider uploading reports for the commit 3469d9d to get more accurate results

@@            Coverage Diff             @@
##             main    #1814      +/-   ##
==========================================
- Coverage   98.89%   98.85%   -0.05%     
==========================================
  Files         111      112       +1     
  Lines        4713     4796      +83     
==========================================
+ Hits         4661     4741      +80     
- Misses         52       55       +3     

Impacted Files	Coverage Δ
R/get_source_expressions.R	93.93% <50.00%> (-0.46%)	⬇️
R/lint.R	96.72% <95.83%> (-0.07%)	⬇️
R/implicit_assignment_linter.R	100.00% <100.00%> (ø)
R/indentation_linter.R	100.00% <100.00%> (ø)
R/linter_tags.R	97.43% <100.00%> (+0.06%)	⬆️
R/xml_nodes_to_lints.R	100.00% <100.00%> (ø)

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[IndrajeetPatil]

Converting back to draft because found a bunch of false positives.

[AshesITR]

I feel like you need following-sibling everywhere you use following.

axis	description
following	Selects everything in the document after the closing tag of the current node
following-sibling	Selects all siblings after the current node

• https://www.w3schools.com/xml/xpath_axes.asp

[IndrajeetPatil]

I feel like you need following-sibling everywhere you use following.

Thanks! Yes, that was indeed the problem.
In my mind, I was thinking about sibling, but somehow wrote down just following.