TODO

Built-ins where to_ast() fails:

[?] Adobe_glyphs -- This is not a function; unclear how/what rstatic should do with this or how it relates to code analysis.
[?] tools::charset_to_Unicode -- This is not a function.

package:stats - selfStart objects

[1] "SSasymp"     "SSasympOff"  "SSasympOrig" "SSbiexp"    
[5] "SSfol"       "SSfpl"       "SSgompertz"  "SSlogis"    
[9] "SSmicmen"    "SSweibull"

These are functions that have unusual classes.

Warnings about formals(args(fn)) on primitives that do not have named parameters.
Code Normalization
- pull out if-statements nested in other expressions
- pull out loops nested in other expressions
- determine evaluation order of default arguments
- collapse namespaces onto symbols
- repeat is while (TRUE)
- replacement functions: parse trees represent length(x) <- 6 as "<-"(length(x), 6) but the meaning is "length<-"(x, 6). That is, this is a call to a replacement function, not an assignment to a call.
- explicit return() at end of function
- non-breaking: dead code after return(), next, break
Code Analysis
- Collect reads correctly for replacement functions, function definitions, and any other missing cases. These need unit tests!
- Collect global uses by called functions. Currently toSSA() only detects global uses in the function being converted to SSA form (and not in the functions that function calls).
Syntax Objects (ASTNode subclasses)
- ...
- S4
- Closures (Functions must to keep track of parent environment)
- <<-
- (
- break and next
- invisible()
- Functions
- [ and [[
- Namespace operators :: and :::?

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