array literals uses typed arrays; fix a jsgen bug (#16850)

* array litterals uses typed arrays
* Update compiler/jsgen.nim

Co-authored-by: Timothee Cour <timothee.cour2@gmail.com>
Co-authored-by: Andreas Rumpf <rumpf_a@web.de>

1 files changed, 39 insertions, 16 deletions

diff --git a/compiler/jsgen.nim b/compiler/jsgen.nim
index 1bf204c0f..04009250e 100644
--- a/compiler/jsgen.nim
+++ b/compiler/jsgen.nim
@@ -1991,6 +1991,23 @@ proc genMove(p: PProc; n: PNode; r: var TCompRes) =
   genReset(p, n)
   #lineF(p, "$1 = $2;$n", [dest.rdLoc, src.rdLoc])
 
+proc genJSArrayConstr(p: PProc, n: PNode, r: var TCompRes) =
+  var a: TCompRes
+  r.res = rope("[")
+  r.kind = resExpr
+  for i in 0 ..< n.len:
+    if i > 0: r.res.add(", ")
+    gen(p, n[i], a)
+    if a.typ == etyBaseIndex:
+      r.res.addf("[$1, $2]", [a.address, a.res])
+    else:
+      if not needsNoCopy(p, n[i]):
+        let typ = n[i].typ.skipTypes(abstractInst)
+        useMagic(p, "nimCopy")
+        a.res = "nimCopy(null, $1, $2)" % [a.rdLoc, genTypeInfo(p, typ)]
+      r.res.add(a.res)
+  r.res.add("]")
+
 proc genMagic(p: PProc, n: PNode, r: var TCompRes) =
   var
     a: TCompRes
@@ -2054,8 +2071,9 @@ proc genMagic(p: PProc, n: PNode, r: var TCompRes) =
   of mNew, mNewFinalize: genNew(p, n)
   of mChr: gen(p, n[1], r)
   of mArrToSeq:
-    if needsNoCopy(p, n[1]):
-      gen(p, n[1], r)
+    # only array literals doesn't need copy
+    if n[1].kind == nkBracket:
+      genJSArrayConstr(p, n[1], r)
     else:
       var x: TCompRes
       gen(p, n[1], x)
@@ -2172,21 +2190,26 @@ proc genSetConstr(p: PProc, n: PNode, r: var TCompRes) =
     r.res = tmp
 
 proc genArrayConstr(p: PProc, n: PNode, r: var TCompRes) =
-  var a: TCompRes
-  r.res = rope("[")
-  r.kind = resExpr
-  for i in 0..<n.len:
-    if i > 0: r.res.add(", ")
-    gen(p, n[i], a)
-    if a.typ == etyBaseIndex:
-      r.res.addf("[$1, $2]", [a.address, a.res])
-    else:
-      if not needsNoCopy(p, n[i]):
-        let typ = n[i].typ.skipTypes(abstractInst)
-        useMagic(p, "nimCopy")
-        a.res = "nimCopy(null, $1, $2)" % [a.rdLoc, genTypeInfo(p, typ)]
+  ## Constructs array or sequence.
+  ## Nim array of uint8..uint32, int8..int32 maps to JS typed arrays.
+  ## Nim sequence maps to JS array.
+  var t = skipTypes(n.typ, abstractInst)
+  let e = elemType(t)
+  let jsTyp = arrayTypeForElemType(e)
+  if skipTypes(n.typ, abstractVarRange).kind != tySequence and jsTyp.len > 0:
+    # generate typed array
+    # for example Nim generates `new Uint8Array([1, 2, 3])` for `[byte(1), 2, 3]`
+    # TODO use `set` or loop to initialize typed array which improves performances in some situations
+    var a: TCompRes
+    r.res = "new $1([" % [rope(jsTyp)]
+    r.kind = resExpr
+    for i in 0 ..< n.len:
+      if i > 0: r.res.add(", ")
+      gen(p, n[i], a)
       r.res.add(a.res)
-  r.res.add("]")
+    r.res.add("])")
+  else:
+    genJSArrayConstr(p, n, r)
 
 proc genTupleConstr(p: PProc, n: PNode, r: var TCompRes) =
   var a: TCompRes