From 039f57ec4bff170ca0379b638623e2a132342fe8 Mon Sep 17 00:00:00 2001
From: Araq <rumpf_a@web.de>
Date: Fri, 23 Oct 2020 10:33:41 +0200
Subject: [PATCH] fixes #15533 [backport:1.4]

---
 compiler/sigmatch.nim                     | 10 +++++++---
 tests/views/treject_var_inside_option.nim | 12 ++++++++++++
 2 files changed, 19 insertions(+), 3 deletions(-)
 create mode 100644 tests/views/treject_var_inside_option.nim

diff --git a/compiler/sigmatch.nim b/compiler/sigmatch.nim
index 687634e932..2b5b70a0b8 100644
--- a/compiler/sigmatch.nim
+++ b/compiler/sigmatch.nim
@@ -92,6 +92,7 @@ type
     isSubtype,
     isSubrange,              # subrange of the wanted type; no type conversion
                              # but apart from that counts as ``isSubtype``
+    isVarConvertible,
     isBothMetaConvertible    # generic proc parameter was matched against
                              # generic type, e.g., map(mySeq, x=>x+1),
                              # maybe recoverable by rerun if the parameter is
@@ -1191,7 +1192,10 @@ proc typeRel(c: var TCandidate, f, aOrig: PType,
   of tyFloat128: result = handleFloatRange(f, a)
   of tyVar, tyLent:
     if aOrig.kind == f.kind: result = typeRel(c, f.base, aOrig.base, flags)
-    else: result = typeRel(c, f.base, aOrig, flags + {trNoCovariance})
+    else:
+      result = typeRel(c, f.base, aOrig, flags + {trNoCovariance})
+      if result > isVarConvertible:
+        result = isVarConvertible
     subtypeCheck()
   of tyArray:
     case a.kind
@@ -1976,7 +1980,7 @@ proc incMatches(m: var TCandidate; r: TTypeRelation; convMatch = 1) =
   of isFromIntLit: inc(m.intConvMatches, 256)
   of isInferredConvertible:
     inc(m.convMatches)
-  of isEqual: inc(m.exactMatches)
+  of isEqual, isVarConvertible: inc(m.exactMatches)
   of isNone: discard
 
 template matchesVoidProc(t: PType): bool =
@@ -2126,7 +2130,7 @@ proc paramTypesMatchAux(m: var TCandidate, f, a: PType,
     # ``isIntConv`` and ``isIntLit`` here:
     inc(m.intConvMatches, 256)
     result = implicitConv(nkHiddenStdConv, f, arg, m, c)
-  of isEqual:
+  of isEqual, isVarConvertible:
     inc(m.exactMatches)
     result = arg
     if skipTypes(f, abstractVar-{tyTypeDesc}).kind == tyTuple or
diff --git a/tests/views/treject_var_inside_option.nim b/tests/views/treject_var_inside_option.nim
new file mode 100644
index 0000000000..e441fda7e1
--- /dev/null
+++ b/tests/views/treject_var_inside_option.nim
@@ -0,0 +1,12 @@
+discard """
+  errormsg: "type mismatch: got <Option[system.int]> but expected 'Option[var int]'"
+  cmd: "nim check $file"
+  line: 12
+"""
+
+# bug #15533
+
+{.experimental: "views".}
+import options
+var a = [1, 2, 3, 4]
+let o: Option[var int] = some(a[0])