fixes #5597; wrong eager template instantiation in generic context (#5601)

compiler/semgnrc.nim

@@ -51,10 +51,10 @@ template macroToExpand(s): untyped =
   s.kind in {skMacro, skTemplate} and (s.typ.len == 1 or sfAllUntyped in s.flags)
 
 template macroToExpandSym(s): untyped =
-  s.kind in {skMacro, skTemplate} and (s.typ.len == 1)
+  s.kind in {skMacro, skTemplate} and (s.typ.len == 1) and not fromDotExpr
 
 proc semGenericStmtSymbol(c: PContext, n: PNode, s: PSym,
-                          ctx: var GenericCtx): PNode =
+                          ctx: var GenericCtx; fromDotExpr=false): PNode =
   semIdeForTemplateOrGenericCheck(n, ctx.cursorInBody)
   incl(s.flags, sfUsed)
   case s.kind
@@ -145,7 +145,7 @@ proc fuzzyLookup(c: PContext, n: PNode, flags: TSemGenericFlags,
       elif s.name.id in ctx.toMixin:
         result = newDot(result, symChoice(c, n, s, scForceOpen))
       else:
-        let syms = semGenericStmtSymbol(c, n, s, ctx)
+        let syms = semGenericStmtSymbol(c, n, s, ctx, fromDotExpr=true)
         if syms.kind == nkSym:
           let choice = symChoice(c, n, s, scForceOpen)
           choice.kind = nkClosedSymChoice

tests/generics/t1050.nim

@@ -14,3 +14,16 @@ proc arrayItem(a: ArrayType): auto =
 var arr: ArrayType[int]
 echo arrayItem(arr)
 
+# bug #5597
+
+template fail() = "what"
+
+proc g[T](x: var T) =
+  x.fail = 3
+
+type
+  Obj = object
+    fail: int
+
+var y: Obj
+g y