Fix #7977: Disallow unsupported pattern in summonFrom

compiler/src/dotty/tools/dotc/typer/Applications.scala

@@ -915,6 +915,13 @@ trait Applications extends Compatibility {
             // applications of inline functions.
             tree.args match {
               case (arg @ Match(EmptyTree, cases)) :: Nil =>
+                cases.foreach {
+                  case CaseDef(Typed(_: Ident, _), _, _) => // OK
+                  case CaseDef(Bind(_, Typed(_: Ident, _)), _, _) => // OK
+                  case CaseDef(Ident(name), _, _) if name == nme.WILDCARD => // Ok
+                  case CaseDef(pat, _, _) =>
+                    ctx.error("Unexpected pattern for summonFrom. Expeced `x: T` or `_`", pat.sourcePos)
+                }
                 typed(untpd.InlineMatch(EmptyTree, cases).withSpan(arg.span), pt)
               case _ =>
                 errorTree(tree, em"argument to summonFrom must be a pattern matching closure")

tests/neg/i7977.scala

@@ -0,0 +1,28 @@
+import scala.compiletime.summonFrom
+class Main(b: Boolean) {
+  inline def foo(): Any = {
+    summonFrom {
+      case x => println(x) // error
+    }
+
+    summonFrom {
+      case x if b => println(x) // error
+    }
+
+    summonFrom {
+      case Some(x) if b => println(x) // error
+    }
+
+    summonFrom {
+      case x if b => println(x) // error
+      case _ => println()
+    }
+
+    summonFrom { // ok but useless
+      case _ if b => println()
+      case _ => println()
+    }
+  }
+
+  foo()
+}