Restore R 3.6 compatibility (#200)

Part of #173

.github/workflows/R-CMD-check.yaml

@@ -37,6 +37,9 @@ jobs:
           - {os: ubuntu-latest,  r: 'oldrel-3'}
           - {os: ubuntu-latest,  r: 'oldrel-4'}
 
+          - {os: ubuntu-latest,  r: '3.6'}
+
+
     env:
       GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}
       R_KEEP_PKG_SOURCE: yes

DESCRIPTION

@@ -23,7 +23,7 @@ License: MIT + file LICENSE
 URL: https://evaluate.r-lib.org/, https://github.com/r-lib/evaluate
 BugReports: https://github.com/r-lib/evaluate/issues
 Depends:
-    R (>= 4.0.0)
+    R (>= 3.6.0)
 Suggests:
     covr,
     ggplot2 (>= 3.3.6),

R/parse_all.R

@@ -112,8 +112,10 @@ parse_all.character <- function(x, filename = NULL, allow_error = FALSE) {
   # parse() drops comments and whitespace so we add them back in
   gaps <- data.frame(start = c(1, pos$end + 1), end = c(pos$start - 1, n))
   gaps <- gaps[gaps$start <= gaps$end, ,]
-  # in sequence(), nvec is equivalent to length.out
-  lines <- sequence(from = gaps$start, nvec = gaps$end - gaps$start + 1)
+  # some indexing magic in order to vectorise the extraction
+  lengths <- gaps$end - gaps$start + 1
+  lines <- sequence(lengths) + rep(gaps$start, lengths) - 1
+
   comments <- data.frame(
     src = x[lines],
     expr = empty_expr(length(lines)),

R/utils.R

@@ -50,3 +50,7 @@ can_parse <- function(x) {
     error = function(e) FALSE
   )
 }
+
+deparse1 <- function (expr, collapse = " ", width.cutoff = 500L, ...) {
+  paste(deparse(expr, width.cutoff, ...), collapse = collapse)
+}