Compilation Error and #637 is not helpful

Summary:

After following #637, still received errors when attempting to run 8schools.stan.

Description:

Windows 7, R 3.5.3 rstan 2.18.2. Followed guidance and #637, but still got error for the simplest 8schools example.

Reproducible Steps:

sessionInfo()
R version 3.5.3 (2019-03-11)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 7 x64 (build 7601) Service Pack 1

Matrix products: default

locale:
[1] LC_COLLATE=English_United States.1252
[2] LC_CTYPE=English_United States.1252
[3] LC_MONETARY=English_United States.1252
[4] LC_NUMERIC=C
[5] LC_TIME=English_United States.1252

attached base packages:
[1] stats graphics grDevices utils datasets methods
[7] base

loaded via a namespace (and not attached):
[1] compiler_3.5.3 tools_3.5.3 yaml_2.2.0

My Makevars.win looks as follows:
CXX14=$(BINPREF)g++ -O2 -march=native -mtune=native
CXX14FLAGS=-O3 -march=native -mtune=native
CXX11FLAGS=-O3 -march=native -mtune=native

Sys.which("g++")
"C:\Rtools\mingw_32\bin\G__~1.EXE"

Current Output:

fit <- stan(file = 'schools.stan', data = schools_dat)
Error in compileCode(f, code, language = language, verbose = verbose) :
Compilation ERROR, function(s)/method(s) not created! file1c8060ad4ca8.cpp:8:39: fatal error: stan/model/model_header.hpp: No such file or directory
#include <stan/model/model_header.hpp>
^
compilation terminated.
make: *** [C:/PROGRA1/R/R-351.3/etc/x64/Makeconf:215: file1c8060ad4ca8.o] Error 1
In addition: Warning message:
In system(cmd, intern = !verbose) :
running command 'C:/PROGRA1/R/R-351.3/bin/x64/R CMD SHLIB file1c8060ad4ca8.cpp 2> file1c8060ad4ca8.cpp.err.txt' had status 1
Error in sink(type = "output") : invalid connection

Expected Output:

Run 8schools example.

RStan Version:

2.18.2

R Version:

3.5.3

Operating System:

Windows 7 x64

Reproduce the failure with the 8schools example using schools.stan and the reported fit <- stan(...) entry point, then inspect Makevars.win and the compiler output for why stan/model/model_header.hpp is not found. Done means the 8schools example compiles and runs on the reported Windows and RStan versions.