cmd/compile: rewrite f(g()) for multi-value g() during typecheck

This CL moves order.go's copyRet logic for rewriting f(g()) into t1,
t2, ... = g(); f(t1, t2, ...) earlier into typecheck. This allows the
rest of the compiler to stop worrying about multi-value functions
appearing outside of OAS2FUNC nodes.

This changes compiler behavior in a few observable ways:

1. Typechecking error messages for builtin functions now use general
case error messages rather than unnecessarily differing ones.

2. Because f(g()) is rewritten before inlining, saved inline bodies
now see the rewritten form too. This could be addressed, but doesn't
seem worthwhile.

3. Most notably, this simplifies escape analysis and fixes a memory
corruption issue in esc.go. See #29197 for details.

Fixes #15992.
Fixes #29197.

Change-Id: I86a70668301efeec8fbd11fe2d242e359a3ad0af
Reviewed-on: https://go-review.googlesource.com/c/153841
Reviewed-by: Robert Griesemer <gri@golang.org>

1 files changed, 3 insertions, 3 deletions

diff --git a/test/cmplx.go b/test/cmplx.go
index dedf2bd8d3..d63c7ebc7e 100644
--- a/test/cmplx.go
+++ b/test/cmplx.go
@@ -49,10 +49,10 @@ func main() {
 	_ = complex(f64, F64) // ERROR "complex"
 	_ = complex(F64, f64) // ERROR "complex"
 
-	_ = complex(F1()) // ERROR "expects two arguments.*returns 1"
-	_ = complex(F3()) // ERROR "expects two arguments.*returns 3"
+	_ = complex(F1()) // ERROR "not enough arguments"
+	_ = complex(F3()) // ERROR "too many arguments"
 
-	_ = complex() // ERROR "missing argument"
+	_ = complex() // ERROR "not enough arguments"
 
 	c128 = complex(f32, f32) // ERROR "cannot use"
 	c64 = complex(f64, f64)  // ERROR "cannot use"