many bugfixes for js (#14158)

* many bugfixes for js

fixes #12672, fixes #14153, closes #14123, closes #11331, fixes #11783, fixes #13966, fixes #14087, fixes #14117, closes #12256.

mostly fixes the fact that it was allowed to assign to newly created temp variables. additionally attempts to get rid of null initialized seqs/strings (though they might pop up here and there); this simplifies a lot of things and makes code size smaller. even if null seqs/strings pop up here and there it's still better than all those bugs existing.

* formatting fixes

* CI fixes

* more CI fixes

2 files changed, 16 insertions, 23 deletions

diff --git a/lib/system/jssys.nim b/lib/system/jssys.nim
index 98a7a2032..106283490 100644
--- a/lib/system/jssys.nim
+++ b/lib/system/jssys.nim
@@ -397,24 +397,29 @@ else:
     """.}
 
 # Arithmetic:
+proc checkOverflowInt(a: int) {.asmNoStackFrame, compilerproc.} =
+  asm """
+    if (`a` > 2147483647 || `a` < -2147483648) `raiseOverflow`();
+  """
+
 proc addInt(a, b: int): int {.asmNoStackFrame, compilerproc.} =
   asm """
     var result = `a` + `b`;
-    if (result > 2147483647 || result < -2147483648) `raiseOverflow`();
+    `checkOverflowInt`(result);
     return result;
   """
 
 proc subInt(a, b: int): int {.asmNoStackFrame, compilerproc.} =
   asm """
     var result = `a` - `b`;
-    if (result > 2147483647 || result < -2147483648) `raiseOverflow`();
+    `checkOverflowInt`(result);
     return result;
   """
 
 proc mulInt(a, b: int): int {.asmNoStackFrame, compilerproc.} =
   asm """
     var result = `a` * `b`;
-    if (result > 2147483647 || result < -2147483648) `raiseOverflow`();
+    `checkOverflowInt`(result);
     return result;
   """
 
@@ -432,27 +437,29 @@ proc modInt(a, b: int): int {.asmNoStackFrame, compilerproc.} =
     return Math.trunc(`a` % `b`);
   """
 
+proc checkOverflowInt64(a: int) {.asmNoStackFrame, compilerproc.} =
+  asm """
+    if (`a` > 9223372036854775807 || `a` < -9223372036854775808) `raiseOverflow`();
+  """
+
 proc addInt64(a, b: int): int {.asmNoStackFrame, compilerproc.} =
   asm """
     var result = `a` + `b`;
-    if (result > 9223372036854775807
-    || result < -9223372036854775808) `raiseOverflow`();
+    `checkOverflowInt64`(result);
     return result;
   """
 
 proc subInt64(a, b: int): int {.asmNoStackFrame, compilerproc.} =
   asm """
     var result = `a` - `b`;
-    if (result > 9223372036854775807
-    || result < -9223372036854775808) `raiseOverflow`();
+    `checkOverflowInt64`(result);
     return result;
   """
 
 proc mulInt64(a, b: int): int {.asmNoStackFrame, compilerproc.} =
   asm """
     var result = `a` * `b`;
-    if (result > 9223372036854775807
-    || result < -9223372036854775808) `raiseOverflow`();
+    `checkOverflowInt64`(result);
     return result;
   """
 
diff --git a/lib/system/reprjs.nim b/lib/system/reprjs.nim
index c45053537..c3f3199a4 100644
--- a/lib/system/reprjs.nim
+++ b/lib/system/reprjs.nim
@@ -130,20 +130,6 @@ proc reprAux(result: var string, p: pointer, typ: PNimType, cl: var ReprClosure)
 
 proc reprArray(a: pointer, typ: PNimType,
               cl: var ReprClosure): string {.compilerRtl.} =
-  var isNilArrayOrSeq: bool
-  # isnil is not enough here as it would try to deref `a` without knowing what's inside
-  {. emit: """
-    if (`a` == null) {
-      `isNilArrayOrSeq` = true;
-    } else if (`a`[0] == null) {
-      `isNilArrayOrSeq` = true;
-    } else {
-      `isNilArrayOrSeq` = false;
-    };
-    """ .}
-  if typ.kind == tySequence and isNilArrayOrSeq:
-    return "nil"
-
   # We prepend @ to seq, the C backend prepends the pointer to the seq.
   result = if typ.kind == tySequence: "@[" else: "["
   var len: int = 0