issue59338.go

     1  // run
     2  
     3  // Copyright 2023 The Go Authors. All rights reserved.
     4  // Use of this source code is governed by a BSD-style
     5  // license that can be found in the LICENSE file.
     6  
     7  // Smoke test for reverse type inference.
     8  // The type checker has more expansive tests.
     9  
    10  package main
    11  
    12  func main() {
    13  	var f1 func(int) int
    14  	f1 = g1
    15  	if f1(1) != g1(1) {
    16  		panic(1)
    17  	}
    18  
    19  	var f2 func(int) string = g2
    20  	if f2(2) != "" {
    21  		panic(2)
    22  	}
    23  
    24  	if g3(g1, 3) != g1(3) {
    25  		panic(3)
    26  	}
    27  
    28  	if g4(g2, 4) != "" {
    29  		panic(4)
    30  	}
    31  }
    32  
    33  func g1[P any](x P) P    { return x }
    34  func g2[P, Q any](x P) Q { var q Q; return q }
    35  
    36  func g3(f1 func(int) int, x int) int       { return f1(x) }
    37  func g4(f2 func(int) string, x int) string { return f2(x) }
    38
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