fixes #19051 [backport:1.6] (#19133)

compiler/sizealignoffsetimpl.nim

@@ -196,6 +196,11 @@ proc computeUnionObjectOffsetsFoldFunction(conf: ConfigRef; n: PNode; packed: bo
     accum.offset = szUnknownSize
 
 proc computeSizeAlign(conf: ConfigRef; typ: PType) =
+  template setSize(typ, s) =
+    typ.size = s
+    typ.align = s
+    typ.paddingAtEnd = 0
+
   ## computes and sets ``size`` and ``align`` members of ``typ``
   assert typ != nil
   let hasSize = typ.size != szUncomputedSize
@@ -445,6 +450,16 @@ proc computeSizeAlign(conf: ConfigRef; typ: PType) =
       typ.size = szUnknownSize
       typ.align = szUnknownSize
       typ.paddingAtEnd = szUnknownSize
+  of tyInt, tyUInt:
+    setSize typ, conf.target.intSize.int16
+  of tyBool, tyChar, tyUInt8, tyInt8:
+    setSize typ, 1
+  of tyInt16, tyUInt16:
+    setSize typ, 2
+  of tyInt32, tyUInt32:
+    setSize typ, 4
+  of tyInt64, tyUInt64:
+    setSize typ, 8
   else:
     typ.size = szUnknownSize
     typ.align = szUnknownSize

tests/ccgbugs/t5296.nim

@@ -1,6 +1,7 @@
 discard """
 cmd: "nim c -d:release $file"
-output: 1
+output: '''1
+-1'''
 """
 
 proc bug() : void =
@@ -12,3 +13,9 @@ proc bug() : void =
         echo x
 
 bug()
+
+# bug #19051
+type GInt[T] = int
+
+var a = 1
+echo -a