disallow juxtaposition with literals ending in .

part of #15731

Author: JeffBezanson

NEWS.md

@@ -82,6 +82,9 @@ Breaking changes
     is now divided among the fields `code`, `slotnames`, `slottypes`, `slotflags`,
     `gensymtypes`, `rettype`, `nargs`, and `isva` in the `LambdaInfo` type ([#15609]).
 
+  * Juxtaposition of numeric literals ending in `.` (e.g. `1.x`) is no longer
+    allowed ([#15731]).
+
 Library improvements
 --------------------
 

src/julia-parser.scm

@@ -323,6 +323,11 @@
                    (string.sub s 1)
                    s)
                r is-float32-literal)))
+      (if (and (eqv? #\. (string.char s (string.dec s (length s))))
+               (let ((nxt (peek-char port)))
+                 (or (identifier-start-char? nxt)
+                     (memv nxt '(#\( #\[ #\{ #\@ #\` #\~ #\")))))
+          (error (string "invalid numeric constant \"" s (peek-char port) "\"")))
       ;; n is #f for integers > typemax(UInt64)
       (cond (is-hex-float-literal (numchk n s) (double n))
             ((eq? pred char-hex?) (fix-uint-neg neg (sized-uint-literal n s 4)))
@@ -815,27 +820,33 @@
               (- num)))
       num))
 
-; given an expression and the next token, is there a juxtaposition
-; operator between them?
-(define (juxtapose? expr t)
+;; given an expression and the next token, is there a juxtaposition
+;; operator between them?
+(define (juxtapose? s expr t)
   (and (or (number? expr)
            (large-number? expr)
            (not (number? t))    ;; disallow "x.3" and "sqrt(2)2"
            ;; to allow x'y as a special case
            #;(and (pair? expr) (memq (car expr) '(|'| |.'|))
                 (not (memv t '(#\( #\[ #\{))))
            )
+       (not (ts:space? s))
        (not (operator? t))
        (not (initial-reserved-word? t))
        (not (closing-token? t))
        (not (newline? t))
-       (not (and (pair? expr) (syntactic-unary-op? (car expr))))))
+       (not (and (pair? expr) (syntactic-unary-op? (car expr))))
+       ;; TODO: this would disallow juxtaposition with 0, which is ambiguous
+       ;; with e.g. hex literals `0x...`. however this is used for `0im`, which
+       ;; we might not want to break.
+       #;(or (not (and (eq? expr 0)
+                     (symbol? t)))
+           (error (string "invalid numeric constant \"" expr t "\"")))))
 
 (define (parse-juxtapose ex s)
   (let ((next (peek-token s)))
     ;; numeric literal juxtaposition is a unary operator
-    (cond ((and (juxtapose? ex next)
-                (not (ts:space? s)))
+    (cond ((juxtapose? s ex next)
            (begin
              #;(if (and (number? ex) (= ex 0))
                  (error "juxtaposition with literal \"0\""))

test/fft.jl

@@ -11,9 +11,9 @@ m4 = [16.    2     3    13;
 
 true_fft_m4 = [
     34.            34.            34.            34.;
-     7. - 1.im  -5. + 3.im  -3. + 5.im   1. - 7.im;
+     7. - 1.0im  -5. + 3.0im  -3. + 5.0im   1. - 7.0im;
     16.           -16.           -16.            16.;
-     7. + 1.im  -5. - 3.im  -3. - 5.im   1. + 7.im ]
+     7. + 1.0im  -5. - 3.0im  -3. - 5.0im   1. + 7.0im ]
 
 true_fftn_m4 = [
  136.        0          0         0 ;

test/linalg/dense.jl

@@ -311,7 +311,7 @@ end
 ## Issue related tests
 # issue #1447
 let
-    A = [1.+0.im 0; 0 1]
+    A = [1.+0.0im 0; 0 1]
     B = pinv(A)
     for i = 1:4
         @test_approx_eq A[i] B[i]

test/sparsedir/sparsevector.jl

@@ -547,9 +547,9 @@ let x = spv_x1, x2 = spv_x2
     @test exact_equal(complex(x, x),
         SparseVector(8, [2,5,6], [1.25+1.25im, -0.75-0.75im, 3.5+3.5im]))
     @test exact_equal(complex(x, x2),
-        SparseVector(8, [1,2,5,6,7], [3.25im, 1.25+4.0im, -0.75+0.im, 3.5-5.5im, -6.0im]))
+        SparseVector(8, [1,2,5,6,7], [3.25im, 1.25+4.0im, -0.75+0.0im, 3.5-5.5im, -6.0im]))
     @test exact_equal(complex(x2, x),
-        SparseVector(8, [1,2,5,6,7], [3.25+0.im, 4.0+1.25im, -0.75im, -5.5+3.5im, -6.0+0.im]))
+        SparseVector(8, [1,2,5,6,7], [3.25+0.0im, 4.0+1.25im, -0.75im, -5.5+3.5im, -6.0+0.0im]))
 
     # real & imag